Home

1771-6.5.15, Bulletin 1771 Communication Controller Module User

1. Timer Ctr 12 Acc Pre Timer Ctr 13 Acc Pre Pre Pre Timer Ctr 15 Acc Acc Pre Timer Ctr 14 Acc Timer Ctr 5 Acc Pre Timer Ctr 8 Pre Pre Pre Timer Ctr 10 Acc Pre Pre Timer Ctr 9 Acc Pre Timer Ctr 6 Timer Ctr 2 Pre Pre Timer Ctr 1 Acc Timer Ctr 3 Timer Ctr 4 Timer Ctr 7 Timer Ctr 11 6 11 Chapter 6 Data Manipulation Binary Code PLC 4 Data Table word Bit Location ref d 10 9 8 7 6 5 4 c A ce N Timer Ctr 16 Acc 1 34 0 0 0 0 0 0 1 0 1 1 0 0 P P P Pre 1 33 0 0 0 0 0 0 1 0 1 1 0 1 P P P Timer Ctr 17 Acc 1 32 0 0 0 0 0 0 1 0 1 1 1 0 P P P Pre 1 31 0 0 0 0 0 0 1 0 1 1 1 1 P P Timer Ctr 18 Acc 1 30 0 0 0 0 0 0 1 1 0 00 0 P P P Pre 1 29 0 0 0 0 0 0 1 1 0 0 0 1 P P P Timer Ctr 19
2. Level 6 Value 0 is the flag byte In this case it indicates that the addresses for levels 3 5 and 6 specified the bytes that follow Default values are used for the levels 1 2 and 4 is the value of the level 3 address is a delimeter that says the next two bytes are one address is the low byte of the level 5 address is the high byte of the level 5 address Note that bytes 4 and 5 together give a value of 260 for the level 5 address is the value of the level 6 address Even though it is the default value it must be specified because itis the last level in the desired extended address 11160 1 6 9 Chapter 6 Data Manipulation 6 10 In Figure 6 7 the first byte contains the bit flags to indicate which addressing levels are specified In this example only levels 3 5 and 6 are specified default values are used for the other levels In Figure 6 7 the level 5 address is 260 decimal which is too large to fit in one byte Therefore a byte of all 1 s is used to delimit the 2 byte address value for this level The value 260 is then coded low byte first Note that the last level level 6 in this example must be specified in the address field even though it is equal to the default value of zero NOTE PLC 3 controllers can also accept PLC PLC 2 type command messages with the PLC PLC 2 logical addressing format Before sending this type of command to a PL
3. Odd high byte Even low byte 16 Bit Computer Word with Left to Right Byte and Bit Order Bit number decimal 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Value A576 hex 0 1 1 1 0 1 1 0 1 0 1 0 0 1 0 1 after byte swapping Even high byte Odd low byte 16 Bit Computer Word with Left to Right Byte Order and Right to Left Bit Order Bit number decima 15 14 13 12 11 109 8 7 6 5 4 3 2 1 0 Value A576 hex 0 1 1 1 0 1 1 0 1 0 1 0 0 1 0 1 after byte swapping 5 F 4 Even high byte Odd low byte 11159 1 PLC PLC 2 PLC and PLC 2 Family controllers access their data tables by using an octal word address In PLC PLC 2 command messages this type of logical word address must be represented as an equivalent byte address This byte address appears in the 2 byte field labeled ADDR in the message block formats chapter 5 To encode a logical PLC PLC 2 address convert the octal word address to whatever number system you are using in your computer application programs Next double this converted word address to get the corresponding byte address Place the result in the ADDR field low byte first 6 7 Chapter 6 Data Manipulation 6 8 For example to address PLC word 020 you would first convert the octal value 20 to the desired base In this example let s use hexadecimal values Octal 20 is 10 hex Doubling this value gives 20 hex for the byte address You would then code the value 0020 hex in the ADDR field of the mess
4. 4 1 Message Packet Formats 5 1 General deco tine ee De p epHUPEEY eR REFS ea eR as 54 Application Layer 5 1 Network 5 1 Message Packet 5 3 Message Formats 5 7 Data Manipulation 6 1 General Pees 6 1 Data 6 1 Addressing 6 6 Table of Contents Error Reporting Generalis Erb eee noses eco ee ato aa a a a ERROR WORD in User Programming 1771 KG 1771 KA and 1774 KA Modules Error Codes for 1775 KA Internal Error Transmissions Between Computer and Full Duplex Modules Switch Settings Switch Settings Detailed Flow Charts General About This Manual Module Description Introduction Communication Controller Modules cat nos 1771 KE and 1771 KF link intelligent RS 232 C devices to an Allen Bradley Data Highway Each of these modules gives you a choice of two protocols on its RS 232 C link Full duplex Half duplex The 1771 KE and 1771
5. R Routing Subroutine Entry Q Incoming Message Queue 11150 1 Messages do not necessarily arrive at their destination in the same order in which they were sent It is impossible for the network layer to guarantee delivery and in some cases it may not be possible to provide notification of non delivery In particular the network layer does not notify the command executor about non delivery of a reply message Therefore it is advisable that your command initiator maintain a timer for each outstanding command message If the time limit expires before the command initiator receives the corresponding reply to its command it can either re transmit the same command message or indicate an error condition Message Packet Chapter 5 Message Packet Formats If your network layer software cannot deliver a command message it should generate a reply message with an error code in it and send that reply to the command initiator If it cannot deliver a reply message the network layer software should simply destroy the reply without notification to the command executor If your link layer software cannot deliver a message over the RS 232 C link it also should return an error message to the command initiator The message bytes contain unsigned binary data from both the application layer and the network layer Figure 5 2 shows the general format of a command message Network layer fields are shaded The meanings o
6. Terminal Barrier Strip m m ES pe Z E OV dc Enable 5y dc Earth Signal Ground 11118 1 Chapter 3 Installation Figure 3 7 Enable Signal Switches for 1771 KF Module Remove Remove Screws Screws 002 On B Enable signal switches Enable signal switch settings 1 2 1 2 0 0 suf elg PE po UE Lo True Hi True Shaded side is setting 101194 3 Carefully remove the metal cover plate from the module 4 Locate the enable signal switches on the module circuit board These switches are situated on the right side of the circuit board between the indicator lights and the DATA HIGHWAY connector Figure 3 7 5 switches for the type of enable signal issued by the power supply Figure 3 7 shows the settings Low true means that the signal line goes low when the supply s output power is enabled high true means that the signal line goes high when the supply s output power is enabled The enable signal must conform to the following specifications High 3V to 5V DC Low 0 2V to 0 6V DC 3 16 Chapter 3 Installation If the power supply s enable signal does not meet the above specifications then set both enable signal switches 1 and 2 to the OFF position CAUTION
7. Reply Format 44 NX Physical Write This command writes bytes of data into the PC data table or program memory Use this command to download the contents of a computer file into PLC memory Use the SIZE field to specify the number of bytes to be written To specify a number of PC words SIZE should be an even value because PC words are two bytes long Command Format E ADDR DATA Max of 243 bytes N Reply Format se es 5 23 Chapter 5 Message Packet Formats PLC 2 COMMANDS PLC 2 Stations can execute all of the commands in the basic command set They can also execute the following commands which apply only to PLC 2 Family controllers Enter download mode Enter upload mode Exit download upload mode Physical read Physical write Set data table size The above commands are privileged commands This means that only a computer can initiate them Their primary use is for uploading and downloading PLC 2 memory Enter Download Mode This command puts the PLC processor into the download mode Use this command on a PLC 2 station before attempting to send any physical write commands to the station Command Format 07 04 Reply Format Berges When you send an Enter Download Upload mode command the Industrial Terminal Port is disabled until you send an Exit Download Upload mode command When the Industrial Terminal Port is disabled it enters the Mode Se
8. 4 CA e 5 P 5 CB 6 i P T 6 CC 8 e 8 CF Pn pi 11 20 CD e 4 mSS 9 2 22 13 A 11 15 Pin Male 25 Pin Male Connector Connector b Wiring Diagram ee This type of connection includes the DTR signal to allow each end to detect the loss of the other end s ability to communicate If your computer does not provide the DTR signal jumper pins 6 and 8 at the module to pin 11 Connection to a Modem To connect the module to a modem you can use the modem interface cable cat no 1770 CP This cable plugs into the COMPUTER RS 232 C connector on the module and the RS 232 C compatible connector on the modem Figure 3 10 3 22 Chapter 3 Installation The 1770 CP cable is 16 5 feet long If you need a longer cable or a male female adapter cable you can construct your own according to the wiring diagram in Figure 3 10 Connect the cable shield at one end only Be sure that the cable length does not exceed the RS 232 C limit of 50 feet The module can be connected to standard American dial up modems and some European modems Other European standards specify that the DTR signal will make the modem answer the phone whether it is ringing or not causing the phone always to be busy Do not use the module with any type of modem that asserts the DTR signal even while waiting for a call The types of dial up network modems that you can use are Manual these are typically acoustically
9. Protocol Environment Definition To fully define the environment of the protocol the transmitter needs to know where to get the message it sends and the receiver must have a means of disposing of messages These are implementation dependent functions which shall respectively be called the message source and the message sink We assume that the message source supplies one message at a time upon request from the transmitter and requires notification of the success or failure of the transfer to station B before supplying the next message When the message source is empty the transmitter waits in an inactive state until a message is available Whenever the receiver has received a message successfully it attempts to give it to the message sink The possibility exits that the message sink will be full The receiver requires an indication of this Figure 4 6 shows this representation of the protocol environment Message Characteristics Ideally the link protocol should not be at all concerned with the content or form of the message it is transferring However full duplex protocol places the following restrictions on the message that are submitted to it for transfer 1 Minimum size of a valid message is 6 bytes maximum is 250 bytes 2 Some protocol implementations point to point links to a 1771 KG module for example require that the first byte of a message match the station address The receiver will ignore messages that do not contain the
10. XMTG Transmitting a RCVG Receiving RDY Ready to transmit Chapter 3 Installation a Active a CU CPU indicator The XMTG light comes on when the KE KF module is current master of the Data Highway and is transmitting a command or reply message The RCVG light comes on when the module is receiving a command or reply message from another station on the Data Highway If the XMTG and RCVG lights are on at the same time this indicates that the module is current master of the Data Highway and is polling the other stations to transfer mastership The RDY light comes on when the module has a message stored in its transmit buffer and it is waiting to acquire mastership of the Data Highway so it can transmit the message The light remains on as long as the cable between the COMPUTER RS 232 C socket and the interfacing RS 232 C device is properly connected This light will appear to flicker whenever characters are being transmitted across the RS 232 C link If this light goes off check the cable and connectors for possible problems The CPU light comes on for about half a second every time the module transmits or receives a DLE NAK protocol sequence chapter 4 If this light flickers frequently or stays on the RS 232 C link might need better isolation or noise immunity Figure 3 13 Diagnostic Indicators ww ALLEN BRADLEY COMM CONTROL O XMTG Transmitting RC
11. A First Digit Station SW 2 SW 3 SW 4 Data Highway Baud Rate SW 5 Baud Rate Switch 38 400 57 600 recommended 76 800 115 200 A 3 Appendix A Switch Settings Computer Link Baud Rate and Parity SW 6 Baud Rate Switch If you have revisions A G module Switch 4 On Even parity Off No If you have revision H module Switch 4 On Execute diagnostic command Off Pass through diagnostic command A4 Appendix A Switch Settings Figure A 1 1771 KE KF Communication Controller Module Computer Ling Baud Switch Station Data Highway Rate and Diagnostic Assembly Baud Rate Past Through ADDRESS od 2 a od 2 3 N N 0 0 F F F F 69 unn n C9 d d d D d 7 s guo e9 Parity prior to series A revision H A 5 General Appendix Detailed Flow Charts This appendix presents flow charts that give detailed views of an example of software logic for implementing full duplex protocol The flow charts in chapter 4 gave you a simplified view of this software logic We have not shown any error checking or recovery relating to interaction with the modem handshake drive a third process To do this would overly complicate t
12. Diagnostic command 1771 KF module 3 6 Reply message Switch 5 on pire ea 1771 module sin i ae NER 4 peri 1771 KG module PLC 2 15 Data processor Highway Link 1 To other stations Switch 5 off p a 1771 l module 4 4 A 4 A ae J 4 Y X e 1771 KG module PLC 2 15 Data processor Highway Link To other stations 11114 1 Chapter 3 Installation Figure 3 4 Station Number Switch assembly If you want to set this digit If you want to set this First Digit Second and Third Digits Switch Setting Example Station No 037 Station No Digits or on on on on on 11115 3 7 Chapter 3 Installation 3 8 This section for the revision H module only Switch 3 determines whether the module uses and recognizes the following handshaking signals data set ready request to send clear to send data carrier detect and data terminal ready If you want your module to set switch 3 detect and ignore duplicate messages fon accept all messages regardless of duplication Switch 4 determines whether or not the RS 232 C port of the KE KF module can detect duplicate messages transmitted to it If you want to the
13. The 1775 K A module inserts the reply error code in the STS or EXT STS bytes of any reply message packet it returns to a remote station For reply errors there is a direct correlation between the error codes in the STS and EXT STS bytes of reply messages and the error codes stored at the command station Refer to section titled PLC 3 below Transmissions Between Computer and Full Duplex Modules for EXT STS bytes The meaning of each error code depends on the command message received from the remote station The sections below described the error conditions that the various commands can generate The error codes are listed according to the decimal value that would be stored at the command initiating station 7 13 Chapter 7 Error Reporting When a remote station transmits one of the commands listed below the local 1775 KA module might issue a reply message that contains one of the error codes listed under that command Error codes 81 to 88 appear in the STS byte of the reply message and codes 231 to 241 appear in the EXT STS byte PLC 3 and PLC family processors can only display error codes contained in the STS byte 80 89 Error codes contained in the EXT STS bytes are only available if either another PLC 3 or computer originates the command message Chapter 7 Error Reporting Diagnostic Read Command EXT STS Code STS Code Error if applicable if applicable Code Possible Causes 10 81 1 A 2 byte ADDR fie
14. Ty Allen Bradley Bulletin 1771 Communication Controller Module Cat No 1771 KE KF User Manual Table of Contents 1 1 Generali 2028 wk ad Sb 21 1 About This 1 1 Module Description 1 1 Specifications dus da cade vee 1 3 5 1 3 Communication Concepts 2 1 General ssi debi tbs herd E cA ees 2 1 Physical Link Layer 2 1 Software 2 8 instalation 242 2e onm Rory 3 1 Generals iied eo hee Pa Sok Qed to bb Reges edens 3 1 Communication Option Switches 3 1 Mounting 5 25 ume ies Shwe bedded be oo eee RES 3 1 Power SUDDly 3 14 Interface Connections 3 17 Diagnostic Indicators 3 2 RS 232 C Link Protocols 4 1 General eee ee ei a Se ade beds 4 1 Definition of Link Protocol 41 Full Duplex 4 2 Half Duplex Protocol
15. 9 FO 239 There are more than 65 535 words in the source file A FO 240 Sum of total transaction size and the word level of PLC 3 addressing is greater than 65 535 B FO 241 Source station does not have access to the destination file 7 17 Chapter 7 Error Reporting PLC 3 Read Commands EXT STS Code STS Code Error if applicable if applicable Code Possible Causes 81 1 There is more than one byte of data after the byte address 2 Number of bytes to read is odd 3 Number of bytes to read is zero 4 Number of bytes to read is greater than the maximum allowed in a reply packet 244 5 Sum of packet offset and size of data in words is greater than 65 535 6 Sum of packet offset and size of data in words is greater than the total transaction size 83 The local 1775 KA module has executed a shutdown request 84 Backplane error either memory parity or timeout disconnect 87 Local PLC 3 is in program mode 1 FO 231 Error in converting the block address major section gt 63 context gt 15 section gt 15 2 FO 232 Three or fewer addressing levels specified in for a PLC 3 word address 3 FO 233 Conversion of a file address to block address resulted in more than 9 addressing levels 4 FO 234 Symbolic address not found 5 FO 235 Symbolic address is of length zero or is longer than 8 bytes 6 FO 236 1 File not found 2 Destination address does not have enough levels to specify a PLC 3 word for word range reads o
16. Any two successive messages between polls that have the same sequence number fields and the same command reply bit are assumed to be duplicates Aborts Counts the number of aborts received The HDLC abort signal is not used on the Data Highway but can be detected by the SIO in certain circumstances Some stations whose addresses match the ringing pattern after a transmitter shutoff can be particularly susceptible to this error stations 36 76 and 176 for example These numbers will depend on highway configurations Transmitted messages A 16 bit counter that records the number of messages successfully transmitted Received messages A 16 bit counter that records the number of messages successfully received Commands send A 16 bit counter that records the number of command messages that were successfully generated as the result of a start bit being set Some of these messages may not be recorded as being transmitted either because they were not successfully sent or because they were sent to the same station that originated them Messages executed A 16 bit counter that records the number of command messages that were received to be executed from the highway This count does not depend on whether execution was successful For each message counted as received a reply message is sent Chapter 7 Error Reporting 25 Replies received A 16 bit counter that records the number of reply messages that were received that resulted in the
17. Chapter 4 RS 232 C Link Protocol Figure 4 16 Implementation of Half Duplex Protocol XCVR 3 Y Select Station ied Y Poll Selected Station Y Start Timeout Receive No DLE Yes Set Active Station Flag Network Layer has Message to send Yes Y Get Message from Network Layer X Y Send Message Y Start Timeout Received DLE ACK Timeouts for this Message Tell Network Layer of Failure Receive Message Active Station 3 Timeouts for this Poll Yes Y No MORE Duplicate Message No Give Message to Network Layer r Y Send DLE ACK Remove Station from Active List 4 30 11141 1 Chapter 4 RS 232 C Link Protocol When a DLE ACK is received the message currently held is discarded When the next poll is received the next message available from the message source is sent or a DLE EOT When a DLE NAK is received the transceiver takes messages from the source until it is empty Each message will be discarded with an error code sent back to the message source This can be used by the master to clear up the message source buffers of all slaves after the master has been down Half Duplex Protocol Diagrams The f
18. Never set switches 1 and 2 both ON Doing so disables the 1771 KF module If you want this enable signal Set switch issued None High True Low True Do not use 6 Replace the metal cover plate and screws After setting the enable signal switches connect the power supply cable to the terminal strip at the bottom of the module Figure 3 6 Figure 3 6 illustrates the terminal strip which should be connected as follows 1 Connect the right most terminal to earth ground If the module is mounted inside an enclosure that is already connected to earth ground then you may connect the right most terminal to the grounding bus of the enclosure instead 2 Connect the zero volt or ground lead from the power supply to the first terminal on the left 3 Connect the 5V DC lead from the power supply to the third terminal from the left 4 Ifthe power supply has an enable signal line connect this line to the second terminal from the left Interface Connections The KE KF module has 3 connectors on its front edge Figure 3 8 The top connector labeled DATA HIGHWAY connects to the Data Highway dropline cable Plug the 15 pin connector of the dropline into the DATA HIGHWAY socket For details on how to construct the dropline refer to publication 1770 810 or 1770 925 The center connector labeled DATA HIGHWAY MONITOR is for future product development Do not make any connections to this socket Chapter 3 Insta
19. Word symbol address DST SR MD ST TNS FNC PACKET TOTAL ge gest wu ASCII symbol WIF SIZE 8 characters max 01 B File symbol address plus word offset DST R MDI ST TN FNC PACKET TOTAL ost sc E OFFSET TRANS ASCII symbol W F WORD SIZE 8 characters max 01 OFFSET C Logical address DST SRC CMD STS TNS FNC PACKET TOTAL fqwolsis is ae Ts PLC 3 logical address SIZE 92 51 bytes Reply Format This is the same as the reply packet format for all current unprotected protected and privilege reads A Format when successful execution DATA Max of 244 bytes or 122 words 4F Format when reporting an error 4F STS Where the extended status byte is optional 5 35 Chapter 5 Message Packet Formats 5 36 Word Range Write This is a write command whose starting address is either a word symbol a file symbol plus a word offset or a logical address This starting address must point to a word in a file The function code is 0 zero A special case of this command is the single word write where the data field is only one word long Command Format A Word symbol address DST SRC CMD STS TNS FNC PACKET TOTAL els sle Beer mds ASCII symbol 8 characters max B File symbol address plus word offset DST SRC CMD STS TNS FNC PACKET TOTAL PST sre quo sts me ne OFFSET TRANS ASCII symbol WI
20. _7 9 Message formats 5 7 Message packet 5 3 Message transsmission 2 13 Mounting KE KF 3 12 Multidrop configuration 1 4 Multidrop topology 4 20 NAKs set 5 19 Network management layer 2 11 Newtwork layer 5 1 O Octal numbers _6 3 PC Programming to Data Highway 2 3 PC to PC 2 4 peer to peer communication 2 6 Physical link layer 2 1 physical write 5 32 PLC 2 commands 5 24 PLC 3 commands 5 27 PLC 4 commands 5 37 Point to point configuration 1 4 Polling 2 15 Power supply KE KF 3 14 Processor Data Highway interface 2 7 Processor RS 232 C interface 2 7 Protected write 5 18 Protocol definition 4 8 Protocol environment 4 8 Protocol link 4 1 R Read physical 5 39 Reads 2 10 Receiver actions 4 11 Replace KC KD with KE KF 3 11 RS 232 C link features 3 3 RS 232 C Data Highway interface 2 7 S SIZE byte 5 6 Software layers 2 8 Specifications KE KF 1 3 Stand alone links 2 4 Stations 2 2 STS 55 Switch Settings 1 T TNS 5 5 Transmission Codes 4 21 Transmission codes 4 2 Transmitter structured English 4 9 W Write physical 5 39 Writes 2 11 N Rockwell Automation Allen Bradley a Rockwell Automation Business has been helping its customers improve pro a ductivity and quality for more than 90 years We design manufacture and support a broad range Allen Bradley of automation products worldwide They include logic processors power a
21. a one Illegal use of EXIT command Illegal use of STOP command STOP encountered in procedure Attempt to read write a bad address Unable to evaluate the expression in the given base This will occur for example if the argument of a FROM BCD function is not a valid BCD bit pattern It will also occur when invalid characters occur in numeric values e g 57 12X Function being used is not defined Expression is too complex Attempt to divide by zero Bad port specifier That is the character following the is other than H orm User symbol used as part of remote address specification Undefined data following assignment command This error would occur for instance if the modifier UNRPOT were used instead of UNPROT Error in remote specification 1 A character other than or following the station num specification H045 T 2 Something other than EOL PROT OR UNPROT following remote source address 012 95 8 9 Third party transfer That is in an assignment command both the source and the destination were remote addresses Error in evaluating a PLC 2 address or PLC 2 address greater than 65 535 Zero range specified in an assignment command Chapter 7 Error Reporting EXT STS Code STS Code if applicable if applicable 207 Word range specified in destination address 208 Destination and source addresses disagree in type 209 Not of Da
22. mastership passes from one station to another in a round robin fashion During installation you assign each station a unique number between 001 and 376 octal Each master passes mastership to the station with the next higher station number that is requesting mastership All polling arithmetic is performed modulo 256 relative to the station number of the current master For example when the master is 200 octal station 220 will receive mastership before station 177 since 220 is closer in sequence to 200 than is 177 Figure 2 6 illustrates this polling scheme The mechanics of the polling algorithm are essentially transparent to you This is because the communication modules handle this automatically However the polling algorithm does lead to the following basic rules that you should follow to optimize your Data Highway performance Number your stations sequentially whenever possible Keep the number of high priority messages as low as possible Chapter 2 Communication Concepts 2 16 Large numbers of high priority messages slow all traffic on the network In general you should limit the number of high priority messages to less than 1 of the total traffic on the Data Highway Figure 2 6 Polling Scheme 01 075 011 076 010 077 376 110 375 111 374 112 373 113 e e e 303 174 302 175 301 176 300 177 277 200 276 201 275 02 2 274 e e 203 11111 Data Security There are two checks used in Data
23. possibility exists that the message sink will be full The transceiver requires an indication of this Figure 4 15 Slave Transceiver Network Network Packet Link Packet MASTER SLAVE SOURCE TRANSCEIVER RECEIVER SOURCE OK OK m Message Message SINK SINK Full Full Y To Other Slaves Software Software Hardware 11140 1 Message Characteristics Ideally the link protocol should not be at all concerned with the content or form of the messages it is transferring However half duplex protocol places the following restrictions on the messages that are submitted to it for transfer 1 Minimum size of a valid message is 6 bytes maximum is 250 bytes 2 Some protocol implementations require that the first byte of a message match the station address These receivers will ignore messages that do not contain the correct address This filtering is not required since the message sink can also provide the address filtering function 4 27 Chapter 4 RS 232 C Link Protocol 4 28 3 As part of the duplicate message detection algorithm the receiver checks the second third fifth and sixth bytes of each message There must be a difference in at least one of these bytes between a message and its predecessor for it to be recognized as distinct rather than a retransmission of the previous message Master Polling Responsibilities The master polling algorithm
24. 0 gt 1 21 2 0 20 0 7 0 23 0 1x22 4 7 1 21 2 1 20 1 1 0 0 1 0x163 0 1x16 256 10 x 16 160 7x 169 7 01A746 42310 ied 64 Chapter 6 Data Manipulation Figure 6 5 Octal Numbers 1 21 2 1 20 1 1x22 4 0x2 0 98 1x20 21 1x22 4 1 21 2 gt 1 1_ 7 3x8 192 5x8 40 1 1 1 011111 7 80 7 3578 23910 11158 1 Order of Transmission PCs store data in 16 bit 2 byte words The bits in these words are numbered addressed 0 through 17 octal going from right to left within a word as follows PC Word Bis 1 15 14 toj 11 10 07 oef os oaf os c2 In PC memory the words are arranged as shown above However when the KE KF module transmits data over its RS 232 C link it transmits one byte at a time The module always transmits the low byte bits 00 through 07 of a word before the high byte bits 10 through 17 of the same word Also transmits the low bit first within a byte Thus when a PC word is traveling over the RS 232 C link it will look like this First Byte Second Byte Bis os aa osf 021010 tr te ts 14 13 12 n 10 Time This does not present a problem at PC stations on the link because PCs always store and retrieve their data in the same order of low byte first It can however require you to do some extra computer ap
25. 1 2 5 6 7 8 Operating status of PLC 3 processor Bits 0 to 1 0 Program mode 1 Test mode 2 Run mode Bit 2 Not used Bit 3 0 Normal 1 Major processor fault Bit 4 0 Normal 1 Shutdown requested Bit 5 0 Normal 1 Shutdown in effect Bits 6 to 7 Not used Type of station interface Bits 0 to 3 6 1775 KA data highway port 7 1775 KA RS 232 C port Bits 4 to 7 4 PLC 3 processor Current context stored in bits 4 to 7 Thumbwheel number Mode control word The logical address of the mode control word is E0 0 0 8 Starting byte address of the diagnostic counters and timers There is a separate block of diagnostic timers and counters for the data highway port and the RS 232 C port The address given here is the one for the port that received the diagnostic status command Series and revision number of the 1775 KA module Bit 0 to 4 0 Revision A 1 Revision B etc Bits 5 to 7 0 Series A 1 Series B etc Not used The physical address of the unused word of PLC 3 system memory This is the physical address corresponding to the logical address E60 0 0 0 The total number of words in PLC 3 system memory both used and unused This is the physical word address corresponding to the logical address E63 0 0 0 5 17 Chapter 5 Message Packet Formats 5 18 Protected Bit Write This command sets or resets individual bits within limited areas of the PC data table memory I
26. 1771 KC KD switches assembly SW 4 switches 1 2 and 3 SW 5 1 2 Same setting as 1771 KC KD switches assembly SW 5 switches 1 and 2 Sw elt 1 2 3 Same setting as 1771 KC KD switches assembly SW 6 switches 1 2 and 3 4 same settying as 1771 KC KD switches assembly SW 1 switch 5 The RS 232 C port of the KE KF module can communicate at a maximum rate of 19 200 bits per second If your 1771 KC KD module was set to communicate at a higher rate then you might have to make some modifications to your RS 232 C link before installing the replacement KE KF module The 1771 KE module differs from the 1771 KF in the way it is mounted The 1771 KE module mounts in an Allen Bradley Bulletin 1771 I O rack while the 1771 KF module is designed for stand alone mounting In both cases you must mount the KE KF module within 100 cable feet of the Data Highway truckline If you are connecting the module directly to an RS 232 C device you must also mount the module within 50 cable feet of the device If the RS 232 C device is another Allen Bradley communication module you can mount the KE KF module up to 7 000 away from it by using the longline connection section titled Interface Connections If you are using a modem link to connect the KE KF module to the RS 232 C device then the module and the device may be as far apart as the modem link will allow 1771 KE Module To install a 1771 KE module in an Allen Bradley
27. 2 Destination address does not specify a PLC 3 word 3 The PLC 3 address specifies more levels than required 4 Word specified by the PLC 3 address does not exist File is larger than 65 535 words Remote station does not have access to the destination file Remote Error Codes Remote error codes are those reported in a reply message from a remote station that received a command message from the local PLC 3 station These error codes are stored under user symbol ERROR in the local PLC 3 station The meaning of a particular remote error code will vary depending on the type of communication interface module at the remote station For example if the remote station is a PLC 3 processor with a 1775 KA interface module the remote error codes will have the meanings listed above For the meanings of other remote error codes refer to section titled ERROR WORD in User Programming errors 80 89 7 19 Chapter 7 Error Reporting Internal Error Counter 7 20 These counters can be read through the diagnostic read command They are available only to a device that can format the diagnostic commands PC user program is unable to set up a diagnostic command They are used to record events of interest for debugging new highway software and for longer term reliability analysis The counters occupy a block of the internal scratch RAM Most are single byte counters that wrap around to zero when they overflow These counters provi
28. 232 C and Data Highway links The types of commands that a station can transmit and receive vary with the type of processor at that station Chapter 5 describes the commands that each type of PC processor can transmit or receive To program your computer to communicate with a PC use the appropriate command message formats shown in chapter 5 Message Structures All messages on a Data Highway network have the same fundamental structure regardless of their function or destination If you could freeze a block while it is in transmission you would see two types of message bytes Protocol bytes Data bytes The methods by which these bytes are filled is determined by the nature of the station from which the transmission block originates For example if a transaction originates from a PC station the station interface module automatically fills the protocol bytes If the transaction originates from a computer station your computer software must supply the necessary protocol In both cases the data bytes contain information supplied by application programs Command Reply Cycle Any transaction on a Data Highway network consists of two parts A command Areply This provides extra data integrity by ensuring that a required action always returns some sort of status whether an error code or data As a frame of reference the command initiator is always referred to as a local station and reply initiator is always referred to as a r
29. 3 PLC 2 30 Loop Processor Processor 1773 KA 1775 KA 1771 KG Module Module Module 1771 KG 1771 KG 1771 KG Module Module Module PLC 2 30 PLC 2 20 PLC 2 15 Processor Processor Processor Chapter 2 Communication Concepts Figure 2 3 Stand alone Point to Point Link to a Computer Computer 1771 KG Module PLC 2 30 Processor 11108 I Both of the PC to PC links in Figure 2 2 are longline RS 232 C links limited to 7 000 cable feet each If you need a longer distance you can use modems to create such a link Computer to PC A computer can communicate directly with PC through either a point to point or a multidrop RS 232 C link Figure 2 3 shows a point to point link to a computer This is an RS 232 C link limited to 50 cable feet If you need a longer distance you can use modems to create this link Figure 2 4 shows multidrop link between a computer and three PC stations The computer can communicate with each of the PC stations directly This type of configuration requires a modem link 2 5 Chapter 2 Communication Concepts Figure 2 4 Stand Alone Multidrop Link to a Computer Computer MODEM MODEM MODEM MODEM 1771 KG 1775 KA 1771 KG Module Module Module PLC 2 15 PLC 3 PLC 2 30 Processor Processor Processor 11109 1 For a point to p
30. A station consists of a computer or PC processor and the module or modules that interface it with the Data Highway link Within a station that contains a KE KF module an RS 232 C link is required as an auxiliary link to the Data Highway Figure 2 1 shows three such stations One station consists of an Advisor Color Graphic System connected to a KE KF module through an RS 232 C link limited to 50 cable ft Another station consists of a computer interfacing with a KE KF module through modem link that is limited only by the nature of the modems themselves The third such station consists of a 1773 KA module interfacing a PLC 4 Microtrol loop with a KE KF module through longline RS 232 C link limited to 7 000 cable ft If you want a link longer than 7 000 ft you must use modems PC Programming Chapter 2 Communication Concepts All Allen Bradley PC processor can connect to the Data Highway through an appropriate station interface module All of these processors can receive and reply to command messages and some of them can also transmit command messages For an explanation of how to program PCs to send and receive messages refer to the user s manual for the appropriate station interface module Figure 2 1 Data Highway Network PLC 3 Processor Computer 1775 KA Computer Module MODEM 2 RS 232 C Link lt MODEM 50 Cable
31. Acc 1 28 0 0 0 0 0 0 1 1 0 0 1 0 P P P Pre 1 27 0 0 0 0 0 0 1 1 0 0 1 1 P P PJH Timer Ctr 20 Acc 1 26 0 0 0 0 0 0 1 1 0 1 0 0 P P P Pre 1 25 0 0 0 0 0 0 1 1 0 1 0 1 P P PJH Timer Ctr 21 Acc 1 24 0 0 0 0 0 0 1 1 0 1 1 0 P P P Pre 1 23 0 0 0 0 0 0 1 1 0 1 1 1 P P P Timer Ctr 22 Acc 1 22 0 0 0 0 0 0 1 1 1 0 0 0 P P P Pre 1 21 0 0 0 0 0 0 1 1 1 0 0 1 P P P IH Timer Ctr 23 Acc 1 20 0 0 0 0 0 0 1 1 1 0 1 0 P 1 19 0 0 0 0 0 0 1 1 1 0 1 1 P P PJH Timer Ctr 24 Acc 1 18 0 0 0 0 0 0 1 1 1 1 0 0 P P IH 1 17 0 0 0 0 0 0 1 1 1 1 0 1 P P P Timer Ctr 25 Acc 1 16 0 0 0 0 0 0 1 1 1 1 1 0 P 1 15 0 0 0 0 0 0 1 1 1 1 1 1 P P PJH Timer Ctr 26 Acc 1 14 0 0 0 0 0 1 0 0 0 00 0 P P P JH Pre 1 18 0 0 0 0 0 1 0 0 0 0 0 1 P P P Timer Ctr 27 Acc 1 12 0 0 0 0 0 1 0 0 0 0 1 0 P P P Pre 1 11 0 0 0 0 0 1 0 0 0 0 1 1 P P P Timer Ctr 28 Acc 1 10 0 0 0 0 0 1 0 0 0 1 0 0 P P P Pre 1 9 0 0 0 0 0 1 0 0 0 1 0 41 P P P Timer Ctr 29 Acc 1 8 0 0 0 0 0 1 0 0 0 1 1 0 P P Pre 1 7 0 0 0 0 0 1 0 0 0 1 1 1 P P PJH Timer Ctr 30 Acc 1 6 0 0 0 0 0 1 0 0 1 00 0 P P P Pre 1 5 0 0 0 0 0 1 0 0 1 0 0 1 P P P Timer Ctr 31 Acc 14 0 0 0 0 0 1 0 0 1 0 1 0 P P P Pre 1 3 0 0 0 0 0 1 0 0 1 0 1 1 P P P Timer Ctr 32 Acc 1 2 0 0 0 0 0 1 0 0 1 1 0 0 P P P Pre 1 0 0 0 0 0 1 0 0 1 1 0 1 P P P These are the number of words which can be read or written to a given location These co
32. C port 1771 KA 1774 KA Data Highway Counters only 0 CRC error on ACK 1 ACK timeout Counts the number of times that the sender timed out waiting for an acknowledgement This is a common error and will be one of the first to respond to reflections or low level noise on the highway It seems to be especially sensitive to problems on longer cables It will also show up often if the receiver or transmitter circuitry on a module is marginal or if the cable connections are loose 2 Contention Counts the number of times contention was detected This will also show up quickly on noisy or overlength cables This counter corresponds to error 93 If 93 is a common error on a highway system then expect 37 start bit timeout errors also since any reply that experiences contention will not be re tried 10 11 Chapter 7 Error Reporting Bad ACK status Counts the number of times the ACK was successfully received but contained a nonzero status code other than memory full Currently the only other implemented ACK code is buffer overflow This condition should never occur except when debugging new code Returned messages Counts the number of times the highway driver returns a message to sender Each count corresponds to one local error bit set or one reply message lost Transmit memory full Counts the number of times that the receiving station s memory was full Each time this happens the message is placed on a waiting queue f
33. DLE STX Circuit BA DLE STX DLE ACK DLE ETX BCC DLE ACK DLE STX embedded response ACK on AB delayed slightly because ETX BCC are indivisible Embedded Response Option To allow simplification of the design of the receiver in some cases you can disable transmission of embedded responses by turning off communication option switch 2 of switch group SW 1 If this switch is off the KE KF module s multiplexer will not allow response codes to be sent within a message Instead it will delay response codes until after it receives the next DLE ETX BCC sequence Half duplex protocol is an alternate link protocol to full duplex protocol You can select this protocol by turning on communication option switch 1 of switch assembly SW 1 Half duplex protocol is based on full duplex but extends or redefines several features Half duplex protocol is a multidrop protocol for one master and one or more slaves Modems must be used unless there is only one slave The units have slave mode capability only the master function must currently be provided by a user programmed intelligent device 4 19 Chapter 4 RS 232 C Link Protocol 4 20 Half duplex protocol provides a lower effective utilization of resources than full duplex but it is much easier to implement Its use is indicated by the following Multiple stations and a single computer are connected in a multidrop configuration using multi drop modems Half duplex modems are
34. Ft Max Link MODEM 1771 KF Module 1771 KF Module Data Highway Link 1771 KF Module Longline RS 232 C Link gt 7 000 Cable Ft Max 1771 KA 1773 KA 1771 KG Module Module Module PLC 2 15 PLC 4 PLC 2 30 Processor Loop Processor 11106 1 2 3 Chapter 2 Communication Concepts 2 4 Computer Programming The communication protocol for the Data Highway link is transparent to a computer on the network However for a computer to send or receive messages through the Data Highway network it must be programmed to communicate with its KE KF module over an RS 232 C link Chapters 4 5 and 6 describe the protocol that you must program your computer to use on this RS 232 C link Stand Alone Links A stand alone communication link is totally separate from any Data Highway network Through use of interface modules other than the KE KF your computer can communicate directly with one or more PCs over an RS 232 C link Two PCs can also communicate directly over a similar RS 232 C link PC to PC Figure 2 2 shows two possible stand alone PC to PC communication links Each is a point to point link in which two PC processors can communicate as peers Ladder diagram programs in the PC processors initiate the transfer of messages between stations Figure 2 2 Stand alone PC to PC Links PLC 4 PLC
35. Graphics 1 3 Application layer 2 8 5 1 Applications 1 3 Basic command set 5 9 Bit write protected 5 18 Bit write unprotected 5 20 Bit Writes 5 29 C CMD and FNC 5 4 Command structures 2 10 Communication Controller Modules 1 1 Communication option switches 3 1 Computer programming 2 4 Computer to PC communication 2 5 Configurations 2 6 Cyclic Redundancy Check 4 25 D Data Highway LAN 2 2 Data Highway Link 2 1 Data Highway link communication rate Index Data link layer 2 12 Data manipulation 6 1 Data security 2 16 DATA field 5 7 Decimal numbers 6 3 Diagnostic commands 2 11 Diagnostic indicators 3 26 Diagnostic status 5 11 Diagnostice status 5 26 DST and SRC 5 4 E ENQ set 5 19 Error checking 2 12 Error codes reply 7 13 Error codes internal 7 20 Error codes local 7 10 Error codes remote 7 19 Error number 7 3 Error reporting 7 1 Error word user programming 7 1 F Floating master 2 13 Flow charts B 1 Full Duplex Protocol diagram 4 15 4 13 Full Duplex Protocol receiver Full Duplex receiver routine 22 H Half Duplex Protocl implementation 4 30 Half Duplex protocol 4 19 Half Duplex Protocol diagrams 4 31 Hexadecimal numbers 6 3 Highway counters 7 20 Installation 3 1 Index Interface connections KE KF 3 17 K Keying 3 13 L Link disconnect _2 1 Local and Remote error bits
36. Local Reply Remote Local errors are those that the 1775 KA module encounters while trying to execute one of its own message procedures Reply errors are those that the 1775 KA module inserts in the STS byte of a reply that it generates in response to a command from a remote station Remote errors are those that are returned to the 1775 KA module in a reply message from a remote Data Highway station NOTE The frame of reference in this chapter is that of the 1775 KA All error codes listed here are a result of some action of a 1775 KA Error 93 is rare but not impossible on a well functioning highway If it persists the internal diagnostic counters should be used to pinpoint the location of the faulty module or cable This error code corresponds with STS code 03 7 9 Chapter 7 Error Reporting Local Error Codes The 1775 KA module stores local error codes under the user symbol ERROR Possible local errors are as listed below EXT STS Code STS Code Error if applicable if applicable Code Meaning 32 The size of the local file involved in a file assignment command is greater than 65 535 bytes 34 A station number greater than 376 octal was specified for the remote address in an assignment command 35 Attempt to send unprotected command is invalid 37 The per packet timeout which can be set through LIST ran out before a reply was received This means that the remote station acknowl edged ACK the command mes
37. Reply Format A Format when successful execution leah B Format when reporting an error 4E STS Where the extended status byte is optional Physical Write With Mask This command sets or resets bits ina memory word of the selected controller The ADDRESS field contains the physical PLC 4 address of the memory word to be modified Refer to chapter 6 for a description of physical addresses The BIT MASK field specifies which bits in the PLC 4 word are to be modified and the DATA field specifies whether those bits are to be set or reset For each bit that is 1 in the BIT MASK the corresponding bit is the addresses PLC 4 word is set to the same value 1 or 0 as the corresponding bit in the DATA field For each bit that is 0 in the BIT MASK the corresponding bit of the addresses PLC 4 word is left unchanged Note that you can modify up to 40 PLC 4 words in this way by specifying a series of ADDRESS DATA and BIT MASK fields Command Format 0E OF sel ADDR DATA BIT MOVE repeated up tp 40 times Reply Format A Format when successful execution poma B Format when reporting an error Emo 4E STS Where the extended status byte is optional Chapter 5 Message Packet Formats Set To Program Mode This command sets the selected controller to the Program Load mode Command Format 0E 0i sel Reply Format A Format when successful execution 4E B Format when reporting an error 4E S
38. TIMEOUT D Appendix B Detailed Flow Charts Scheduled By e STARTTIME Aborted By e STOPTIME WAKEUP Wake Up the Process Sleeping at WTRESP If Any RETURN 11169 1 B 7 Appendix B Detailed Flow Charts Figure B 8 GETMSG Subroutine SLEEP Go to Sleep At WTMSG No Indivisible Zone UNLINK Common w WTMSG Remove a Message From W Output Queue Queue Output A Message Boxed area above must be executed indivisibly i e with the scheduler or RETURN interrupts disabled depending on implementation B 8 Appendix B Detailed Flow Charts Figure B 9 SIGOK SIGFAIL Subroutine SIGOK SIGFAIL Place Success Place Failed Code in Message Code in Message Control Block Control Block LINK Place Message on RETURN Queue WAKEUP NET Implementation Dependent Procedure to Tell Network Layer that RETURN Queue Entry Has Been Made RETURN 11171 1 9 Appendix B Detailed Flow Charts Figure B 10 Sharing the Transmit Side of the UART XMIT RCVE M lt TXALLOC rae i UART Usage Not In Use gt Signal hs lt XMIT RCVE Since the tramsit side of the UART is shared by the transmit and receive processes a mutual exclusion mechanism is used to gain sole access during transmission of each indivisible code sequence T
39. TTE e 06 00 Reply Format E DATA Max of 243 bytes Diagnostic Read This command reads up to 244 bytes of data from the PROM or RAM of the station interface module You can use it to read the module s diagnostic timers and counters Use the diagnostic status command to obtain the starting address of the diagnostic counters Command Format 06 01 Reply Format E DATA Maxof244 bytes 4 N Chapter 5 Message Packet Formats Diagnostic Status This command reads a block of status information from the station interface module The reply to this command contains the status information in its DATA field Command Format 06 03 Reply Format a STS is DATA Max of 244 bytes 4 y The status information varies with the type of station interface module Table 5 A describes the contents of the status DATA field for 1771 KA 1771 KC KD 1771 KE KF 1771 KG and 1174 KA modules Table 5 B lists the status DATA for 1773 KA module Table 5 C describes this DATA for 1775 KA modules 5 11 Chapter 5 Message Packet Formats Table 5 A Contents of Status DATA for 1771 KA 1771 KC KD 1771 KE KF 1771 KG and 1774 KA Modules 1 Operating status of PC processor Bits 0 to 2 0 Program load mode 1 Test mode 2 Run mode 3 not used 5 Remote test 4 Remote program load 6 Remote run monitor PLC Bit 3 0 Normal 1 No communication with PC Bit
40. This command initializes or clears memory in the selected PLC 4 controller Use this command to clear the data table memory of the controller before downloading to it The controller must be in program load mode and must not be executing any other privileged command Command Format 0E 0C sel Chapter 5 Message Packet Formats Reply Format A Format when successful execution Gece B Format when reporting an error 4 STS Where the extended status byte is optional Physical Read This command reads the specified number of bytes from the memory of the selected PLC 4 controller Use this command to upload the contents of PLC 4 memory to your computer The SIZE field contains the number of bytes to be read and it may have a value from 1 to 242 decimal Command Format 0E 00 Reply Format A Format when successful execution 4E B Format when reporting an error 4 STS Where the extended status byte is optional Physical Write This command writes bytes of data into the memory of the selected PLC 4 controller Use this command to download data from your computer to the controller The PLC 4 ADDRESS field contains the physical byte address where the data will begin being written into PLC 4 memory Refer to chapter 6 for a description of this physical address Command Format OE 0E sel _ address DATA 1 239 bytes 5 39 Chapter 5 Message Packet Formats 5 40
41. applicable STS Code if applicable 125 126 127 129 140 142 143 144 145 146 147 148 149 150 154 156 159 160 161 163 Chapter 7 Error Reporting Illegal modifier for the CREATE command That is the command was CREATE and the was other than LOCAL GLOBAL or a legal abbreviation of one of these The CREATE command was specified but the symbol did not begin with an missing in CREATE system symbol address Attempt to delete nonexistent symbol Unrecognized or ambiguous command cf error 124 Illegal data following GOTO command Illegal use of label e g not in a procedure Label not found Duplicate label User symbols must be distinct from labels Too many nested procedures Insufficient privilege for the specified operation This error can occur when an attempt is made via the assignment command to write into a major section of memory in which the 1775 KA module does not have access privileges namely major section 0 1 or 2 Unbalanced parenthesis in expression A procedure name was used in a field that required a symbolic ad dress or a user symbol variable A label was used in a field that required a symbolic address or a user symbol variable Error in reading address for symbol entry Illegal symbol in expression Bad level specified in extended address 1 More than 9 levels were specified in an extended address 2 Some
42. because the noise is mistaken for a poll response and the wrong station is selected as the next master When this occurs the old master resumes polling It also can happen on a long highway if the poll response is very attenuated and is not picked up by the carrier detect circuit If the new station does respond but the old master does not hear it the old master will record a false poll and continue polling and the new master will start polling also This usually leads to the second station detecting contention and relinquishing Receiver heard status Counts the number of times that the receiver received a status frame instead of a message frame This should only occur if a poll timeout is imminent a master has had mastership for more than 170 ms and the station has disabled its address recognizer to test for any valid traffic The probability of errors in 8 9 and 10 increases substantially Frame too small Counts the number of frames that were rejected because the header was incomplete This should only be counted because of undebugged software or in the unlikely event that a bad frame fooled the CRC checker Wrong destination address Counts the number of frames that were rejected because the destination address was incorrect This can have the same cause as 8 This counter also detects frames that have the same source and destination address Receiver memory full Counts the number of times that the receiver sent an ACK without fir
43. between the desired word and the beginning of the addressed file The offset is zero for the first word of a file In word range read and write commands this field can be combined with a symbolic file address to specify a word address 5 28 Chapter 5 Message Packet Formats Bit Writes This is a bit write command to modify the bits at the address specified by either a word symbol a file symbol plus a word offset or a logical address This address must point to a word within a file The function code is 2 Unlike the current unprotected and protected bit writes in the basic command set this command can be change the bits in a single word only Command Format A Word symbol address ASCII bol co WIF SET RESET Mask Mask 00 B File symbol address plus word offset ASCII bol eee T sa W F WORD SET RESET 01 Mask Mask C Logical address N DST FNC PLC 3 logical address rise Mask Mask Reply Format This is the same as the reply packet format for all current unprotected protected and privileged bit writes A Format when successful execution 4F B Format when reporting an error 4F STS Where the extended status byte is optional 5 29 Chapter 5 Message Packet Formats 5 30 Download Request A computer can use this command to inform the 1775 KA module that it wants to do a download If the 17
44. can be read only by issuing a diagnostic read command from a device connected to one of the modules that supports an RS 232 C port The section titled Transmissions Between Computer and Full Duplex Modules explains the STS byte that is contained in the command header This data is presented as part of the RS 232 protocol and is available only to modules that support this e g KE KF module A brief note Error codes pointing to traffic problems or other ambiguous situations should be dealt with only after a troubleshooter has thoroughly tested the highway cabling for shorts and bad connections Most application problems can be traced initially to bad cabling What can be very frustrating is that bad cabling does not necessarily mean that a point is completely shorted or completely open Some traffic may get through narrowed bandwidth but the frequency of re tries on a given message becomes very high An error code word specified in the header rung is the primary source of explanation for programming problems and runtime problems Error codes are stored in this word for most events that can be observed by a Data Highway user It is important to note that the display of an error code at a given location does not necessarily mean a faulted condition exists on the highway Due to the nature of the polling algorithm and the built in re try and recovery procedures random noise or contention can easily be ignored if normal procedures are fo
45. correct address Chapter 4 RS 232 C Link Protocol SOURCE Figure 4 6 Protocol Environment Network Network Packet Path 1 Packet Transmitter Receiver o I fg i A SINK Status Path 2 Full Software Software Hardware gt 11131 1 3 part of the duplicate message detection algorithm the receiver checks the second third fifth and sixth bytes of each message There must be a difference in at least one of these bytes between a message and the previous one for it to be recognized as distinct rather than a retransmission of the previous message If switch 3 of switch group SW 1 is off the KE KF module does not implement duplicate message detection section titled RS 232 C Link Features Revisions Protocol Definition Whenever the message source can supply a message and the transmitter is not busy it sends a message packet on path 1 It then starts a timeout and waits for a response on path 2 When a DLE ACK is received the message has been successfully transferred After signaling the message source that the message has been sent the transmitter proceeds with the next message If a DLE NAK is received the message will be retransmitted The transmitter restarts the timeout and waits again for a response This can be repeated several times There is a user defined limit to the number of ti
46. data bits represents one hexadecimal digit between 0 and F In this way each 16 bit data word can have a hexadecimal value between and FFFF Each digit of a hexadecimal number has a place value that is a multiple of 16 To convert a hexadecimal number to its decimal equivalent multiply each hexadecimal digit by its corresponding place value and add the results of the multiplications Figure 6 4 shows the hexadecimal representation of the decimal number 423 Octal The octal number system is also a relatively easy way to represent binary data This system uses the eight digits through 7 Each group of three data bits represents one octal digit between 0 and 7 This factor presents a slight conversion problem because bytes and words usually contain an even number of bits Thus an 8 bit byte can have an octal value between 0 and 377 while 16 bit word can have an octal value between 0 and 177777 6 3 Chapter 6 Data Manipulation Each digit of an octal number has a place value that is a multiple of 8 To convert from octal to decimal multiply each octal digit by its corresponding place value and add the results of the multiplications Figure 6 5 shows the octal representation of the decimal number 239 Figure 6 4 Hexadecimal Numbers 0x 23 0 0 22 0 016 0x2 0 0x20 0 0x23 20 0x22 0 116 0 21 0 1x20 z 1 1x23 8 0x22
47. existing application without having to make any changes in your application programs If you have revision A G module In Set Switch Switch Assembly Number off 2 Same setting as 1771 KC KD switch assembly SW 1 switch 1 3 off 4 off 5 Same setting as 1771 KC KD switch assembly SW 1 Switch 5 SW 2 1 2 Same setting as 1771 KC KD switches assembly SW 2 switches 1 and 2 SW 3 1 2 3 Same setting as 1771 KC KD switches assembly SW 3 switches 1 2 and 3 SW 4 1 2 3 Same setting as 1771 KC KD switches assembly SW 4 switches 1 2 and 3 SW 5 1 2 Same setting as 1771 KC KD switches assembly SW 5 switches 1 and 2 sw elt 1 2 3 Same setting as 1771 KC KD switches assembly SW 6 switches 1 2 and 3 4 off The RS 232 C port of the KE KF module can communicate at a maximum rate of 19 200 bits per second If your 1771 KC KD module was set to communicate at a higher rate then you might have to make some modifications to your RS 232 C link before installing the replacement KE KF module 3 11 Chapter 3 Installation Mounting 3 12 If you have revision H module In Set Switch Switch Assembly Number SW 1 1 off 2 Same setting as 1771 KC KD switch assembly SW 1 switch 1 3 off 4 off 5 off SW 2 1 2 Same setting as 1771 KC KD switches assembly SW 2 switches 1 and 2 SW 3 1 2 3 Same setting as 1771 KC KD switches assembly SW 3 switches 1 2 and 3 SW 4 1 2 3 Same setting as
48. for the KE KF module is 128 cycles or about 3 seconds Command Format 06 04 Reply Format corni Set Variables This command is a combination of the above three commands It sets the maximum ENQs NAKs and timeout all at once Put the timeout setting in the first byte of the DATA field the NAKs setting in the second byte and the ENQs in the third byte If you do not specify a data value for any one the variables in this command that variable is automatically reset to zero Command Format Enea 06 02 Reply Format je afe 46 Unprotected Bit Write This command sets or resets individual bits in any area of PC data table memory The data field in this packet consists of 4 byte blocks each of which contains a 16 bit address field a set mask and a reset mask Use the ADDR field to specify the address of the byte to be modified in the PC data table memory Put the low byte least significant bits of the PC address value into the first byte of the ADDR field Refer to chapter 6 for more details on how to specify an address value Use the SET mask to specify which bits to set to 1 in the addressed PC byte A 1 in a bit position of the SET mask means to set the corresponding bit in the addressed PC byte to 1 a O in a bit position of the SET mask means to leave the corresponding bit in the PC byte unchanged Chapter 5 Message Packet Formats Use the RESET mask to specify which bits to reset to 0 in
49. frames that have the same source and destination address Receiver memory full Counts the number of times that the receiver sent an ACK without first being able to allocate a receiver buffer This may result in a memory overflow error when the next message is received Bad frame status Counts the number of frames that were rejected because of a bad CRC This error is very common on a noisy highway Buffer overflow Counts the number of times a message was received that contained more than 250 bytes Memory overflow Counts the number of times a message was received when there was no buffer space allocated for it This usually follows a memory full error Retransmits Counts the number of duplicate frames received A duplicate frame is sent by a transmitter when it fails to receive an ACK If the reason it failed to receive an ACK was that the ACK was lost rather than 7 27 Chapter 7 Error Reporting 7 28 16 17 18 19 20 because the original message was lost the duplicate is redundant and should be discarded Any two successive messages between polls that have the same sequence number fields and the same command reply bit are assumed to be duplicates Aborts Counts the number of aborts received The HDLC abort signal is not used on the Data Highway but can be detected by the SIO in certain circumstances Some stations whose addresses match the ringing pattern after a transmitter shutoff can be particul
50. in the EXT STS byte the STS byte will contain FOH which in effect functions as a flag that there has been an error value generated If the STS byte is zero then the EXT STS will also be zero The following is a listing of relevant PLC 3 status codes for both the STS byte and the EXT STS byte Chapter 7 Error Reporting 1 Illegal command or command size 2 Specified data size number of bytes is zero odd or greater than 512 PLC 3 backplane fault occurred during message execution Read write file does not exist PLC 2 addressing violation read write file too small Read write file overflow more than 65 535 words Diagnostic read command attempted to read the PLC 3 backplane window Invalid physical address Attempted to write data past the end of memory Attempted to read data from beyond the end of user program memory Memory protect keyswitch disallows access into file Upload download option is not enabled at the des tination station PLC 3 in Program Mode No file assigned to source station 04 to 07 in STS Byte F Extended error format look in the EXT STS byte for the error code Error in conversion of block address Improper format for PLC 3 word address EXT STS byte Error in conversion of file address Invalid symbol Improper symbol specification format 6 Invalid PLC 3 word address 7 Improper file size File size changed during message execution 9 File size too larg
51. is a write command where the starting address is a PLC 3 physical address It is used to download to a PLC 3 from a computer The destination 1775 KA module will accept this command only after the source station has successfully transmitted a shutdown request The function code for this command is 8 Command Format DST SRC CMD STS TNS FNC PLC 3 OF 09 physical address DATA Max of 238 bytes or 119 words Chapter 5 Message Packet Formats Reply Format This is the same as the reply packet format for all current unprotected protected and privileged writes A Format when successful execution spe eese B Format when reporting an error Te Tele eL 4F STS Where the extended status byte is optional Restart Request This command is used by the computer to terminate an upload or a download The computer cannot issue this command until after it has successfully completed an upload or download operation with the destination station This command causes the 1775 KA module to revoke the upload and download privileges for the source computer station and to initialize a PLC 3 restart The function code for this command is 10 decimal Command Format Te Tele Ep OF 0 Reply Format A Format when successful execution spe eese B Format when reporting an error Te Tele er 4F STS Where the extended status byte is optional Shutdown Request This command is used by the computer to ask the
52. is too small then send DLE NAK else if message is too large then send DLE NAK else if header is same as last message send a DLE ACK else if message sink is full send DLE NAK else begin send message to message sink send a DLE ACK save last header end end else if DLE ENQ then send LAST RESPONSE else LAST RESPONSE NAK end GET CODE is defined as loop variable GET CHAR if char is not a DLE begin add char to BCC return the char and data flag end else begin GET CHAR if char is a DLE begin add char to BCC return a DLE and a data flag end else if char is an ACK or NAK send it to the transmitter else if char is an ETK begin 4 14 OK Chapter 4 RS 232 C Link Protocol GET CHAR add char to BCC return ETX with a control flag end else return character with a control flag end end end GET CHAR is defined as an implementation dependent function that returns one byte of data from the link interface hardware Full Duplex Protocol Diagrams The following figures show some events that can occur on the various interfaces Time is represented as increasing from the top of the figure to the bottom Figure 4 9 Normal Message Transfer SOURCE XMTR LINK RCVR SINK Data DLE STX Data DLE ETX BCC gt NotFull Data ACK 11134 1 4 15 Chapter 4 RS 232 C Link Protocol Figure 4 10 Message Transfer w
53. may vary depending on the expected flow of traffic through the system A simple master that does not expect unsolicited messages continuously polls each slave once in a round robin fashion If a message is received it should be handled then the next station polled An alternative scheme would poll each station repeatedly until it was empty and then proceed to the next Relaying of peer to peer messages is best left to the network layer which is the lowest level of the body of software that includes the message source and sink Figure 4 16 is a flowchart of the software logic for implementing half duplex protocol from the master station s point of view Slave Transceiver Actions Since the transceiver receives dirty input from the physical world it must be capable of responding to many adverse situations Some of the things that could conceivably happen are listed below 1 The message sink can be full leaving nowhere to put a message 2 message can contain a parity error 3 BCC can be invalid 4 TheDLE SOH DLE STX or DLE ETX BCC my be missing 5 The message can be too long or too short 6 spurious control or data code can occur outside a message 7 A spurious control code can occur inside a message 8 The DLE ACK response can be lost causing the transmitter to send a duplicate copy of a message that has already been passed to the message sink The slave is always in a passive mode until it receives a messa
54. number of times that this station has tried to relinquish mastership and the station that was expected to take over failed to respond This happens often on a noisy highway because the noise is mistaken for a poll response and the wrong station is selected as the next master When this occurs the old master resumes polling It also can happen on a long highway if the poll response is very attenuated and is not picked up by the carrier detect circuit If the new station does respond but the old master does not hear it the old master will record a false poll and continue polling and the new master will start polling also This usually leads to the second station detecting contention and relinquishing Receiver heard status Counts the number of times that the receiver received a status frame instead of a message frame This counter will never be incremented because the message size is checked first and all status messages are too small to be accepted Frame too small Counts the number of frames that were rejected because they were less than 6 bytes long This counter will record all status frames that were received by a station that disabled its address recognizer in the second step of the mastership timeout process This will happen often on heavily loaded highway Wrong destination address Counts the number of frames that were rejected because the destination address was incorrect This can have the same cause as 9 This counter also detects
55. of messages in the message source which use up all free pool memory In this case the memory can be freed up by receiving messages from the station Waiting for the memory to clear by the action of the station alone may not work since it could be that the only way to free up space is to send a message to the master Chapter 4 RS 232 C Link Protocol Line Monitoring When monitoring half duplex protocol in two wire mode you need to monitor only one line The example below shows a message sent by the master and a reply sent by the slave in response to a poll Slave responses are underlined Message from master to slave DLE SOH stn DLE STX message DLE ETX BCC DLE ACK Message sent from slave to master in response to poll DLE ENQ stn BCC DLE STX message DLE ETX BCC DLE ACK Poll with a DLE EOT in response DLE ENQ stn BCC DLE EOT 4 37 General Application Layer Network Layer Message Packet Formats This chapter describes how your computer application programs should format command and reply messages for transmission over the RS 232 C link It covers both application level and network level functions Basically the application layer specifies the contents of messages and initiates their transmissions The network layer takes the information from the application layer and formats it in a way that is acceptable to the data link layer described in chapter 4 Application programs are of two types command initiators a
56. operation is that no single station disables communication on the Data Highway as long as other stations continue to operate This means that even with disconnection or faulted operation of a module or a processor communication between other operating station interface modules continues This minimizes the need for backup in some applications When a station gains control of the Data Highway to transmit messages it has become a master station All other station interface modules assume a slave mode This enables these stations to receive and acknowledge messages sent to them Basically a station has three states of operation Transmitting messages Polling to determine which station gets mastership next Receiving messages and polls Thus each Data Highway station can transmit and receive both messages and polling sequences Figure 2 5 shows the change of states at a Data Highway station Message Transmission A station must have mastership of the Data Highway before it can transmit any messages or polling sequences As part of the data integrity of the highway all commands must receive a reply before a transaction is considered complete Since the highway treats commands and replies as the same type of message it takes at least one change of mastership to complete a single transaction 2 13 Chapter 2 Communication Concepts 2 14 Any command has to be formatted in the application program of the local or transmitting s
57. set It is possible but not probable that the message will be executed at the remote station The local error bit will be set by this error If the done or remote error bits are set they will occur after the local error bit Reasons for this error include Disconnection of the Data Highway Noise on the highway Bad cabling or connections Remote station is powered off Remote station does not exist Wrong station address is being used Remote module is faulted Some module on the highway is in a bus hog condition and prevents proper operation of the highway If an error 92 persists the internal diagnostic counters should be used to pinpoint the location of the faulty module or cable This error code corresponds with STS code 02 93 This error will occur if the local module while attempting to send a message detects another master on the highway The local error bit for the rung that sent the message will be set Like error 92 this error does not mean that the message was not received It is quite probable that the message will be executed If it is the done bit or remote error bit may be set after the local error bit if the start bit stays on If the start bit is unlatched by the local error bit a 53 or 56 error may result Occurrence of this error is probably related to general highway conditions not to the message or the stations sending and receiving it The message should be re tried Possible causes of t
58. setting of a done or remote error bit 26 27 Breaks Counts the number of breaks sent to the IT 28 Resyncs Counts the number of times the PC driver has to resyncronize with the PC This counter will always count at least one resync because of powerup 29 IT errors Counts down modulo 5 the number of errors on the KA to IT cable Every time this count reaches zero the KA does a handshake to reset the forced I O table in the PC 30 Undeliverable replies Counts the number of replies that were lost because they could not be delivered over the highway Undeliverable commands can be signaled to the user because the user is located in PC memory and can always be reached If a reply message cannot be delivered over the highway there is no way to signal the user of that message who is also over the highway that this station cannot signal a reply The local user is not concerned with the problems of the remote user and can take no meaningful action anyway so there is not much to do but destroy the message and count it 1771 KC NOTE The intelligent device can read the memory of the 1771 KC it is hooked to by setting the destination equal to the module address 0 Bad CRC on ACK 1 timeout Counts the number of times that the sender timed out waiting for an acknowledgement This is a common error and will be one of the first to respond to reflections or low level noise on the highway It seems to be especially s
59. that station In some cases switch settings on the station interface module can disable execution of a particular type of command at that station For more details refer to the user s manual for the station interface module Basic commands are in two categories Privileged Commands n Diagnostic counters reset Diagnostic loop Diagnostic read Diagnostic status Set ENQs Set NAKs Set timeout Set variables Non privileged Commands Protected bit write Protected write Unprotected bit write Unprotected read Unprotected write 1 Computer initiates commands and PCs execute command 2 Computer and PC stations can initiate commands only PCs can execute commands unless the computer is programmed for execution Diagnostic Counters Reset This command resets to zero all the diagnostic timers and counters in the station interface module The diagnostic status command gives the starting address for this block of counters and timers Command Format DST SRC STS TNS FNC 46 07 Reply Format 5 9 Chapter 5 Message Packet Formats 5 10 Diagnostic Loop You can use this command to check the integrity of transmissions over the communication link The command message transmits up to 243 bytes of data to a station interface module The receiving module should reply to this command by transmitting the same data back to the originating station Command Format spe
60. that a message has been successfully received DLE NAK also a response code signals that an attempt to transfer a message has failed DLE ENQ is a message code It requests the re transmission of the last receiver code Link Layer Message Packets A link layer message packet starts with a DLE STX ends with a DLE ETX BCC CRC and includes all link layer data codes in between Data codes can occur only inside a message packet Response codes can also occur between a DLE STX and a DLE ETX BCC CRC but these response codes are not part of the message packet they are referred to as embedded responses Figure 4 1 shows the format of a link layer message packet for full duplex protocol and the layer at which each portion should be implemented At the end of each message packet is the one byte BCC field Block Check The block check character BCC is a means of checking the accuracy of each message packet transmission It is the 2 s complement of the 8 bit sum modulo 256 arithmetic sum of all data bytes between the DLE STX and the DLE ETX BCC CRC It does not include any other message packet codes or response codes For example if message packet contained the data codes 8 9 6 0 2 4 and 3 the message packet codes would be in hex 10 02 08 09 06 00 02 04 03 10 03 EO DLE STX Data DLE ETX BCC CRC The sum of the data bytes in this message packet is 20 hex The BCC is the 2 s complement of this sum or EO hex This is shown in
61. that match the previous message Number of STX full duplex mode or SOH half duplex mode received This is in effect a count of the number of messages that were started Number of messages characters or message fragments that were ignored Number of messages that were aborted by receipt of a DLE ENQ Number of messages that were aborted by the receipt of an unexpected control code other than DLE ENQ Number of times the DLE ACK response was sent but no buffer space for the next message Number of times DLE NAK was sent because there was no buffer Number of broadcast messages received Number of broadcast messages that were successfully received Number of messages seen that were not for this station Number of DLE EOTs sent Number of calls received Number of times that phone was hung up by the module Number of times that DCD was lost Number of times that the phone was hung up because of a DCD timeout 7 29 Chapter 7 Error Reporting 1771 KG Error Counters MODEM CHANNEL COUNTERS 0 16 61 count of the number of times the station attempted to send a message 2 16 bit count of the number of messages that were successfully transmitted and ACKed 4 16 bit count of the number of ACKs that were received 6 Number of ACKs successfully passed from the receiver s separator to the transmitted 7 Number of NAKs received 8 Number of NAKs passed from the separator to the transmitter 9 Num
62. the message sink is full the message is discarded and not acknowledged If while waiting for a message a DLE ENQ is received the transceiver accepts the next two characters The last character is read directly from the link since it is a BCC and is not byte stuffed If the station address does not match or there is an error the poll is ignored If the poll is accepted there are three possible situations 1 transceiver could still be holding a message that it had transmitted previously but had not been ACKed There is a limit on the number of times each message can be sent If this limit is exceeded when the poll is received the message is returned to the message source with an error indication and the transceiver tries to send the next message from the message source If the limit is not exceeded the response to the poll will be to re send the current message 2 no message is currently being held the transceiver tries to get one from the message source If one is available the transceiver will initialize its re try counter and transmit it in response to the poll 3 no message is available the response to a poll will be to transmit a DLE EOT When a message is transmitted after receiving a poll its format is identical to a full duplex message packet After sending a message the transceiver will hold the message until a DLE ACK is received or the number of times the message has been polled exceeds the limit 4 29
63. to an intelligent RS 232 C device if the KE KF module is mounted within 50 cable feet of the device Longline connection to an Allen Bradley 1775 KA 1773 KA or 1771 KG interface module if the KE KF module is within 7 000 cable feet of the other module Modem connection if the KE KF module is within 50 cable feet of an RS 232 C compatible modem You may also use the 1771 KE module to replace a 1771 KC module or the 1771 KF module to replace a 1771 KD module in an existing application By properly setting some option switches on the KE KF module you can make this replacement without having to change any application programs that you were using with the 1771 KC KD module Refer to section titled RS 232 C Communication Rate Parity and Diagnostic Commands in chapter 3 for an explanation of how to set the KE KF option switches Chapter 1 Introduction 1 6 Figure 1 3 Multidrop Link Computer Multidrop Modem Link Modem Modem Modem KE KF Data Highway Link 1771 KG module module PLC 2 15 processor 1775 KA 1773 KA module module PLC 3 titra processor processor Modem Data Highway Link KE KF Mego module KE KF 1771 KA 1774 KA module module module PLC 2 PLC processor processor Computer 11105 1 General Physical Lin
64. ungap of a rung before the zone or by changing the data table size 31 This will not be generated by rev F 1771 KA Previous modules generated this code if the start bit scanner detected a hard error on the PC to module cable 32 The data block of a read or write command is too large to fit in one Data Highway message This error causes the module to enter an error state 33 An invalid command code was detected by the start bit scanner This has the same cause as error 30 This error causes the module to enter an error state 34 An invalid station address was detected by the start bit scanner See error 30 This error causes the module to enter an error state 35 The KA attempted to send an unprotected write or bit control command while the DIP switch that enables unprotected commands was off This can only occur at run time if the DIP switch that controls this option was changed without removing power from the module 36 The start bit was turned off after a message was sent but before the done bit local error or remote error bit was set This is the situation that causes the local error to turn on then off for 85 ms after the start bit 1s reset The error code word is set before the local error bit turns on 37 The start bit was timed out by the automatic module timer before a reply message arrived This happens for one of the following reasons Noise on the highway causes loss of a message In this case the message p
65. ways depending on your application needs Number Systems You may use any one of the following number systems to represent data in your computer application programs Binary Binary coded decimal 1 Decimal Hexadecimal Octal You must design your computer application programs to make any necessary conversions from one number system to another Once you have selected the number system that is best for your applications try to use only that one system and convert all data values to that base to avoid confusion Binary The binary number system is probably the simplest to use for computer and PC applications because it is the most natural way to represent data bits However since the binary system uses only the digits 0 and 1 it is cumbersome to show values in binary format Each digit in a binary number has a certain place value expressed as a power of 2 You can calculate the decimal equivalent of a binary number by multiplying each binary digit by its corresponding place value and then adding the results of the multiplications Figure 6 1 shows the binary representation of the decimal number 239 6 1 Chapter 6 Data Manipulation 6 2 Figure 6 1 Binary Numbers 1x27 128 1x26 64 1x25 32 0 24 0 128 1 23 8 64 32 1x22 4 8 4 1x21z2 0 1x2 1 23910 1l1ililolilililile 111011115 23940 11154 1 Binary Coded Decimal Quite often P
66. 0 NAK 15 The term code means in the following paragraphs an indivisible sequence of one or more bytes having a specific meaning to the link protocol Indivisible means that the component characters of a code must be sent one after another with no other characters inserted between them It does not refer to the timing of the characters This definition has less significance than for full duplex protocol since there is no multiplexing of transmission codes in half duplex protocol 4 21 Chapter 4 RS 232 C Link Protocol These codes are used in half duplex protocol Control Codes DLE SOH DLE STX DLE EXT BCC CRC DLE ACK DLE NAK DLE ENQ DLE EOT Data Codes DATA single characters having values 00 OF and 11 FF DLE DLE to represent the data 10 DLE SOH indicates the start of a message DLE STX separates the link level header from the data field of a message DLE ETX BCC CRC terminates a message DATA 00 OF AND 11 FF encode the corresponding values in the message itself DLE DLE encodes the occurrence of the value 10 hex in the message DLE ACK signals that a message has been successfully received DLE NAK is used as a global link reset command This causes all slaves to cancel all messages that are ready to be transmitted to the master Typically the slave will return the messages to the command originator with an error code DLE ENQ starts a poll command DLE EOT is used by slaves as a response to
67. 1 rack 1771 KF stand alone mounting Communication Ports Data Highway RS 232 C Cabling Data highway Data highway dropline cable cat no 1770 CD RS 232 C Data terminal Interface Cable cat no 1770 CG or Modem Interface Cable cat no 1770 CP Power Requirements 1 2A 5V DC Power Source 1771 KE Bulletin 1771 1 0 rack power supply 1771 KF User supplied Allen Bradley cat no 1771 P2 or similar Ambient Temperature Rating 0 C to 60 C 32 F to 140 F operational 400C to 85 C 40 F to 185 F storage Ambient Humidity Rating 5 to 95 without condensation A KE KF module provides either point to point link or a multidrop link between an Allen Bradley Data Highway and an intelligent RS 232 C device By intelligent RS 232 C device we mean any device that complies with RS 232 C electrical standards and that can be programmed to handle the communication protocol described in chapters 4 through 6 of this manual Throughout this manual we will also use the term computer in a general sense to refer to this type of device Some examples include An Allen Bradley Advisor Color Graphics System A PLC 3 Programmable Controller and connected Communication Adapter Module cat no 1775 KA A PLC 2 Family Programmable Controller and connected PLC 2 Family RS 232 C Interface Module cat no 1771 KG Chapter 1 Introduction A PLC 4 Microtrol Programmable Controller and con
68. 1 B 3 Appendix B Detailed Flow Charts Figure B 3 WTAK Subroutine WTAK STARTTIME Start the ACK Timeout SLEEP Receive No a Response Go to Sleep at WTRESP Yes Indivisible Zone Y STOPTIME Common Cancel the w WTRESP A Sleep Location w RESP A Variable Used to Pass the Response Code From the Receiver to the Transmitter Get the Response Code if Any From RESP RETURN 11165 1 4 Appendix B Detailed Flow Charts Figure B 4 SENDM Subroutine C SENDM B Input Message address Size of message Internal BCC accumulator Reset BCC Message pointer accumulator Message size counter SENDCTL Send DLE STX BCC Link Data D m Include Byte in BCC SENDETX SENDDATA Send DLE ETX BCC Send Link Data Byte RETURN 11166 1 B 5 Appendix B Detailed Flow Charts Figure B 5 STARTTIME Subroutine STARTTIME l An Implementation Dependant Routine that Schedules TIMEOUT to Be Executed at the To of an Interval of Time Typically 12 Character Times RETURN n Figure B 6 STOPTIME Subroutine STOPTIME d An Implementation Dependent Routine to Cancel TIMEOUT RETURN 4 B 6 11167 1 11168 1 Figure B 7 TIMEOUT Subroutine
69. 1 4 Related Data Highway Documentation Publication Number Title 1770 810 Data Highway Cable Assemble and Installation Manual 1770 843 Network Communication Software User s Manual 1770 801 Communication Adapter Module cat no 1771 KA User s Manual 1771 802 Communication Controller Module cat no 1771 KC KD User s Manual 1771 811 PLC 2 Family RS 232 C Interface Module cat no 1771 KG User s Manual 1773 801 PLC 4 Communication Interface Module cat no 1773 KA User s Guide 1774 819 Communication Adapter Module cat no 1774 KA User s Manual 1775 802 PLC 3 Communication Adapter Module cat no 1775 KA User s Manual Figure 1 1 Communication Controller Modules pe eas amp Ig Ty o Q ot z e Cat No 1771 KF 1 2 Specifications Applications Chapter 1 Introduction Table 1 B lists the specifications for a KE KF module Table 1 B KE KF Communication Controller Module Specifications Communication Rates Data highway 57 600 bits per second recommended RS 232 C switch selectable from 110 to 19 200 bits per second Functions Interface a programmable RS 232 C compatible device with an Allen Bradley Data Highway Serve as a replacement for 1771 KC KD Communication Controller Modules Location 1771 KE single slot in Bulletin 177
70. 1775 KA module to initiate either a PLC 3 shutdown if the computer has download privileges or a freeze on file allocations if the computer has upload privileges The computer cannot issue this command until it has successfully transmitted an upload or download request to the 1775 KA module This command has a function code of 7 5 33 Chapter 5 Message Packet Formats Command Format me gels OF 07 Reply Format A Format when successful execution 4F B Format when reporting an error 4F STS Where the extended status byte is optional Upload Request This command is used by the computer to inform the 1775 K A module that it wants to do an upload If the module grants the upload privilege the computer may begin issuing physical reads If a different station already has the upload privilege the second station is denied the privilege The function code is 6 Command Format OF 06 Reply Format A Format when successful execution 4F B Format when reporting an error 4F STS Where the extended status byte is optional Chapter 5 Message Packet Formats Word Range Read This is a read command whose starting address is either a word symbol a file symbol plus a word offset or a block address This starting address must point to a word in a file The function code is 1 A special case of this command is the single word read where the number of bytes to read is only two bytes one word Command Format A
71. 4 0 Normal 1 Download mode Bit 5 0 Normal 1 Format error in communication zone of PC program Bits 6 and 7 Always zero 2 Type of station interface module and processor Bits 0 to 3 0 1771 KC KD module 1 1771 KA module also KA2 2 1774 KA module 3 1771 KE KF module 4 1771 KG module 5 not used 6 1775 KA data highway port 7 1775 KA RS 232 C port 8 1771 KA data highway port 9 1773 KA RS 232 C port Bits 4 to 7 0 PLC processor 1 PLC 2 processor 2 PLC 2 20 1 1 processor 3 Mini PLC 2 processor 4 PLC 3 processor 5 PLC 2 20 LP2 processor 6 PLC 2 15 processor 7 PLC 2 30 processor 5 12 Chapter 5 Message Packet Formats 8 PLC 4 Microtrol processor 15 Computer 3 4 Octal word address of the start of PC program 5 6 Memory size number of bytes for PLC processors zero otherwise 7 8 Starting byte address of diagnostic counters and timers 9 Series and revision level of station interface module Bits 0 to 4 0 Revision A 1 Revision B etc Bits 5 to 7 0 Series A 1 Series B etc KA 2 series B revision A 10 Settings of the option switches on the station interface module This byte is not used in replies by 1771 KC KD or 1771 KE KF modules For the other modules the bits of this byte are defined as follows 1771 KA Module Bits 0 to 1 0 56 700 bits per second 1 76 800 bits per second 2 38 400 bits per second 3 115 200 bit
72. 7 16 PLC PLC 2 Read Commands EXT STS Code STS Code Error if applicable if applicable Code Possible Causes 10 81 1 The required 2 byte ADDR field and 1 byte SIZE field are missing in the command message 2 The ADDR value is odd that is it does not specify a word address 3 The value of SIZE is 0 zero 4 The value of SIZE is greater than 244 5 The SIZE value specifies an odd number of bytes 30 83 Same as for PLC PLC 2 write commands above 40 84 Same as for PLC PLC 2 write commands above 50 85 1 Destination file does not exist 2 Destination file is too small 3 Source file is more than 65 535 words long 70 87 PLC 3 processor is in program mode PLC PLC 2 Bit Write Commands EXT STS Code STS Code Error if applicable if applicable Code Possible Causes 10 81 Incomplete bit description because the number of bytes after the TNSW is not a multiple of 4 30 83 Same as for PLC PLC 2 word write commands above 40 84 Same as for PLC PLC 2 word write commands above 50 85 1 Destination file does not exist 2 Destination bits do not exist in destination file 3 Length of source file is greater than 64 535 words 60 86 Keyswitch setting at local PLC 3 processor prohibits access 70 87 Local PLC 3 processor is in program mode Chapter 7 Error Reporting PLC 3 Write Commands EXT STS Code STS Code Error if applicable if applicable Code Possible Causes 10 81 1 There are not at
73. 75 KA module grants the download privilege the computer may begin issuing physical reads or writes If a different station already has the download privilege the second station is denied the privilege The function code is 5 Command Format OF 05 Reply Format A Format when successful execution 4F B Format when reporting an error 4F STS Where the extended status byte is optional File Read This is a read command whose starting address is either a file symbol or a block address This starting address must point to a file of words The function code is 4 Command Format A File symbol address DST SR MD ST TNS FNC PACKET TOTAL ASCII symbol SIZE 8 characters max B Logical address DST SRC STS TNS FNC PACKET TOTAL PLC 3 logical address SIZE 2 51 bytes Chapter 5 Message Packet Formats Reply Format This is the same as the reply packet format for all current unprotected protected and privileged reads A Format when successful execution DATA Max of 244 bytes or 122 words 4F X B Format when reporting an error 4F STS Where the extended status byte is optional File Write This is a write command whose starting address is either a file symbol or a block address This starting address must point to a file of words The function code is 3 Command Packet Format A File symbol address DST SRC STS TNS FNC PACKET TOTAL P
74. Appendix B Detailed Flow Charts SLEEP Wait For RXD Interrupt at RXDWAIT Disable UART Received Interrupt Check Parity Framing and Receiver Overrun No Get Byte From UART Enable Processor Interrupts RETURN NOTE This figure assumes the use of Z80 510 11189 1 25 Appendix B Detailed Flow Charts Figure B 28 SENDNET Subroutine Input ENDNET e Message Buffer An Implementation Dependent Routine to Put a Message on the INPUT Queue Reset the BUFFER Flag RETURN 11190 1 B 26 Appendix B Detailed Flow Charts Figure B 29 GETBUF Subroutine GETBUF Yes Is there a Buffer Ca Nee z GETFREE Get an Empty Buffer No RETURN Yes Is there a Buffer Save Address of Buffer Set the BUFFER Flag RETURN 11191 1 B 27 Appendix B Detailed Flow Charts Figure B 30 GETFREE Subroutine GETFREE An Implementation Dependent Routine to Try to Allocate an Empty Message Buffer RETURN 1119241 B 28 Symbols Empty 4 2 5 23 7 12 A ACK 7 20 7 23 ADDR 5 6 Addresses logical PLC 4 6 8 Addressing 6 6 PLC 6 13 PLC 2 6 13 PLC 3 6 8 6 14 PLC 4 6 15 PLC 4 Microtrol 6 10 PLC PLC 2 6 7 Addressing symbolic 6 1 Advisor tm Color
75. Bulletin 1771 I O rack follow these steps 1 Turn off all power to the I O rack and to its controlling PC processor Chapter 3 Installation 2 Carefully slide the module into one of the slots in the I O rack 3 Secure the module in the I O rack by snapping down the latch on the top of the slot that contains the module 4 on the power to the PC processor and I O rack Keying The 1771 KE module is keyed to guard against installation in the wrong module slot To implement this protection insert keying bands supplied with your I O chassis into a Keying Positions 11116 1 You can change the position of keying bands if subsequent system design requires the insertion of a different type of module in this slot WARNING Remove system power before removing or installing your module in the 1771 I O chassis Failure to observe this warning could result in damage to module circuitry and or undesired operation with possible injury to personnel 1771 KF Module The rear edge of the 1771 KF module contains a mounting bracket that allows you to mount the module almost anywhere Figure 3 5 gives the mounting dimensions for the module To protect the module from harmful environmental effects enclose it in a standard industrial enclosure NEMA type 12 or similar 3 13 Chapter 3 Installation Power Supply The KE K
76. C 3 station you must first allocate a PLC 3 input file to simulate PLC PLC 2 memory refer to publication 1775 802 In addition PLC 3 controllers can transmit both PLC 3 and PLC PLC 2 type command messages each with its appropriate logical addressing format Therefore if you plan to transmit commands from a PLC 3 to your computer you should set up a computer buffer to simulate a PLC 3 file and write computer application programs that are capable of interpreting all the types of addressing formats that will appear in the command messages PLC 4 Microtrol PLC 4 Microtrol controllers use a form of logical addressing that specifies the identification number of the controller in the loop the section of memory and the bit address To specify a PLC 4 logical address in a command message you would use the appropriate binary code listed in Table 6 A Note that these binary codes let you address only PLC 4 words not bits PLC 4 controllers can accept only PLC PLC 2 type non privileged commands The binary code for the PLC 4 logical address goes in the 2 byte field labeled ADDR in the PLC PLC 2 message block formats chapter 5 Put the low byte bits 0 through 7 of the binary address code into the first byte of ADDR For example suppose we want to address storage word 4 in controller 3 in a PLC 4 Microtrol loop The binary code for this address is 00000000 00110100 In the command message that accesses this storage word the ADDR field woul
77. C data is represented in binary coded decimal BCD form In this system each group of four bits in a PC word represents one decimal number between 0 and 9 In this way each 16 bit word can represent a BCD value between 0 and 9 999 Figure 6 2 shows the BCD representation of the decimal number 239 Figure 6 2 BCD Representation of Decimal 239 0x 23 0 0x22 0 2 1 21 2 0x20 0 0x23 0 0x22 0 3 1x2 2 0x20 0 1x23 8 0x22 0 0x21 0 9 1x20 1 0 0 1 0 0 0 1 11001 11155 1 Chapter 6 Data Manipulation Decimal The decimal number system is probably the easiest for us to use because it is most familiar to us It uses the common digits 0 through 9 and each digit has a place value that is a power of 10 Figure 6 3 However despite the convenience of decimal numbers it is often easier to convert binary data to a number system other than decimal Figure 6 3 Decimal Representation Number 239 2 x 102 20049 29 3x 10 300 9 x 100 919 23910 2 3 9 1 11156 1 Hexadecimal The hexadecimal number system is the most compact way to represent binary data and it allows for the easiest conversion to and from binary This system uses a number set of 16 digits the numbers 0 through 9 and the letter A through F where the letter A through F are equivalent to the decimal numbers 10 through 15 respectively Each group of four
78. EUP without losing would probably be limited to lowever immediate control of the processor Con baud rates text switching would be deferred until B it self executed a SLEEP PROCESS B PROCESS C A Previous Wakeup SLEEP B 18 WAKEUP NOTE Sequence of processor execution is indicated by circled numbers 11181 1 Appendix B Detailed Flow Charts Figure B 20 POWERUP Routine Powerup At powerup the Z 80 starts executing code at location 0 The powerup routine starts the XMIT and RCVE processes by executing a SPAWN A SPAWN is very similar to a WAKEUP except the corresponding SLEEP is imaginary and is located ahead of the first instruction of the SPAWNed process POWERUP SPAWN RCVE SPAWN XMIT Continue Initialization 11182 1 B 19 Appendix B Detailed Flow Charts The Address of a Queue is the Address of its Root NOTE Messages are added to the end of the queue and removed from the head B 20 Figure B 21 Message Queue MESSAGE ROOT CONTROL BLOCKS MESSAGES e FIRST MESSAGE Network Data LAST SIZE Block STATUS NEXT MESSAGE Network Data SIZE Block STATUS L A 0 MESSAGE Network Data SIZE Block STATUS 11153 1 Figure B 22 UNLINK Subroutine An Implementation Depend
79. English procedures Figure 4 7 is a flowchart of the software logic for implementing the transmitter 4 9 Chapter 4 RS 232 C Link Protocol TRANSMITTER is defined as loop Message GET MESSAGE TO SEND Status TRANSFER Message SIGNAL RESULTS Status end TRANSFER Message is defined as initialize nak limit and enq limit SEND Message start timeout loop WAIT for response on path 2 or timeout if received DLE ACK then return SUCCESS else if received DLE NAK then begin if nak limit is exceeded then return FAILURE else begin count NAK re tries SEND MESSAGE message end end else if timeout begin if eng limit is exceeded then return FAILURE else begin count ENQ re tries send DLE ENQ on path 1 start timeout end end end loop send DLE STX on path 1 for every byte in the message do begin add the byte to the BCC send the corresponding data code on path 1 end send DLE ETX BCC on path 1 end GET MESSAGE TO SEND This is an operating system dependent interface routine that waits and allows the rest of the system to run until the message source has supplied a message to be sent SIGNAL RESULTS This is an implementation dependent routine that tells the message source of the results of the attempted message transfer 4 10 Chapter 4 RS 232 C Link Protocol WAIT This is an operating system dependent routine that waits for any of several events to occur while allowing other parts of the system to ru
80. F WORD DATA Max of 226 bytes 8 characters max 01 OFFSET or 113 words C Logical address DST SRC CMD STS TNS FNC PACKET TOTAL PLC 3 logical address DATA Max length is 239 bytes minus the 2 51 bytes length of the PLC 3 block address must be an EXE a of bytes WIF DATA Max of 228 bytes 01 or 114 words Reply Format This is the same as the reply pack format for all current unprotected protected and privileged writes A Format when successful execution spe eese B Format when reporting an error meea 4F STS Where the extended status byte is optional Chapter 5 Message Packet Formats PLC 4 Commands PLC 4 stations can execute all of the commands in the basic command set They can also execute the following commands which apply only to PLC 4 Microtrols Allocate processor De allocate processor Initialize processor Physical read Physical write Physical write with mask Set to program mode Set to run mode Set to single scan test mode Set to test mode The above are privileged commands This means that only a computer can execute them Their primary purpose is for uploading and downloading PLC 4 memory Note that PLC 4 stations cannot initiate any type of command message In addition to the message packet fields already described for the basic command set section titled Message Packet PLC 4 messages may also contain a by
81. F module requires 5V DC power for operation The 1771 KE module obtains this power from the 1771 I O rack in which it is mounted The 1771 KF module needs an independent power supply To provide power to a 1771 KF module use an Allen Bradley power supply cat no 1771 P2 or equivalent The power supply connects to a terminal strip at the bottom of the module Figure 3 6 Use an Allen Bradley power cable cat no 1770 CF to make this connection Before connecting the 1771 KF module to its power supply determine whether the supply issues a signal to indicate that its output power is enabled Some power supplies issue a low true enable signal some issue a high true signal and others issue no enable signal The 1771 KF module contains a set of switches that can be set to accept either of these cases The switches are set incorrectly if all 5 LEDs come on To set these switches do the following Figure 3 5 Mounting Dimensions for 1771 KF Module 10 5 8 75 ARP d T 125 0 625 1111741 1 the module down so that the white identification label is face down and the front edge of the module is to your right 2 Remove the screws from the corners of the metal cover place Figure 3 7 Chapter 3 Installation Figure 3 6 Power Supply Connections for 1771 KF Module o d 2 Em mm AS
82. Highway network message transmission A 16 bit CRC cyclic redundancy check a Data Highway link A 8 bit BCC block check character or a 16 bit CRC series A rev only on an RS 232 C link Some station interface modules also have a switch that lets you select a parity check even parity only on an RS 232 C link A block check is used to detect errors at the link level Beginning with revision H you can select a CRC instead of this block check Any device connected to the RS 232 C link must be capable of generating a BCC A BCC is added to the end of every message block to help detect errors of transmission between station interface modules The command station generates a BCC by first summing every byte of the text excluding control characters then taking the 2 s complement of that sum The result is the BCC Any final carry out bit is ignored in the BCC computations The receiving station also sums the text bytes then adds that sum to the BCC to produce zero Any sum other than zero indicates an error has been made in the transmission and causes the receiving station to respond with DEL NAK Chapter 2 Communication Concepts The CRC is used at the data link layer to validate messages transmitted on the Data Highway link The station interface module at the sending station appends the CRC to the message The CRC is based on the bit pattern of the transmitted message The receiving station also computes a CRC base
83. KF modules perform the same functions They differ only in the way they are mounted and in the way they receive power Where these differences are discussed each module is referenced separately Otherwise both modules are referred to collectively as the KE KF module This manual describes installation operation and communication protocols of the KE KF module and it assumes that you are already thoroughly familiar with how to program your computer or other intelligent RS 232 C device It does not assume prior knowledge of the Allen Bradley Data Highway Table 1 A lists related Data Highway documentation that might be helpful in conjunction with this manual For more details about the programming and operation of specific Allen Bradley programmable controllers refer to the appropriate user s manual for that controller This manual is organized as follows Chapter 2 Explains some Data Highway concepts Chapter 3 Tells how to install a KE KF module Chapters 4 5 and 6 Describe the communication protocol use by a KE KF module Chapter 7 Summarizes error reporting Figure 1 1 shows both the 1771 KE and 1771 KF modules These modules have the following hardware features Diagnostic indicators Connectors for Data Highway and RS 232 C devices a Communication option switches Stand alone mounting bracket 1771 KF only Terminal strip for power supply connection 1771 KF only Chapter 1 Introduction Table
84. RS 232 C signal lines Duplicate message detection Embedded responses Protocol type 11113 1 3 2 Chapter 3 Installation RS 232 C Link Features Revision A G Figure 3 2 illustrates the switches in switch assemblies SW 1 You use these switches to control the special features of the KE KF module s RS 232 C port This section shows you how to control this feature protocol embedded responses duplicate message detection RS 232 C handshaking signals diagnostic commands Protocol Switch number 1 determines what type of protocol the KE KF module uses in communicating through its RS 232 C port If you want your module set switch 1 to have half duplex protocol on This section for revision A G modules only Refer to chapter 4 if you need a description of protocols Embedded Responses Switches 1 and 2 determine whether or not the KE KF module can transmit and receive embedded responses If you want your module to set switch 1 set switch 2 transmit or receive embedded responses Refer to chapter 4 if you need a description of embedded responses 3 3 Chapter 3 Installation 3 4 This section for revision A G modules only Switch 3 determines whether or not the RS 232 C port of the KE KF module can detect duplicate messages transmitted to it Duplicate Messages If you want your module to set switch 3 detect and ignore duplicate messages on
85. SINK SINK MASTER LINK SLAVE NotFull gt DLE ENQ SIN Data DLE STX Noise DLE ETX BCC DLE ENQ SIN gt lt lt DLE STX Data DLE ETX BCC Same Message Data DLE ACK OK Note that the message sent for the second poll is the same as the first since the first transmission was not ACKed 11146 1 4 33 Chapter 4 RS 232 C Link Protocol Figure 4 22 Duplicate Message Transmission SOURCE SOURCE SINK MASTER LINK SLAVE SINK Not Full DLE ENQ SIN BCC Data lt DLE STX Data DLE ETX BCC Data DL Noise CK Sometime Later NotFull DLE ENQ SIN BCG DLE STX Data DLE ETX BCC DLE ACK Discard Retransmission OK gt Note that the message sent for the second poll is the same as the first since the first transmission was not ACKed Also the master should ACK and discard the second message since it was a retransmission This means that the master must either poll a station repeatedly until it receives a DLE EOT without polling any other stations to be sure it has detected all retransmissions If each station is polled only once per cycle the master must keep a record of the last header from each station since other stations may transfer messages between
86. ST sac quo sts ne OFFSET TRANS ASCII symbol DATA Max of 228 bytes or 114 words 8 characters max B Logical address DST SRC STS TNS FNC PACKET TOTAL osr sac ris ruc OFFSET TRANS PLC 3 logical address DATA Max length is 239 bytes minus the 2 51 bytes length of the PLC 3 block address must be an shal as C of bytes Reply Format This is the same as the reply packet format for all current unprotected protected and privileged writes A Format when successful execution 5 31 Chapter 5 Message Packet Formats 5 32 B Format when reporting an error Tele eL 4F STS Where the extended status byte is optional Physical Read This is a read command where the starting address is a PLC 3 physical address It is used to upload from a PLC 3 to a computer The destination 1775 KA module will accept this command only after the source station has successfully transmitted a shutdown request The function code for this command is 9 Command Format DST SRC STS TNS FNC PLC 3 SIZE OF 09 physical address Reply Format This is the same as the reply packet format for all current unprotected protected and privileged reads A Format when successful execution DATA Max of 244 bytes or 122 words 4F X B Format when reporting an error meea 4F STS Where the extended status byte is optional Physical Write This
87. Switch assembly SW 5 Both switches ON for 57 600 bits per second RS 232 C Communication Rate Parity and Diagnostic Commands Switch assembly SW 6 lets you select the communication rate parity and diagnostic commands for the KE KF module s RS 232 C port Switch assembly SW 6 Parity revision A G module Diagnostic commands revision H module Communication rate 3 9 Chapter 3 Installation 3 10 Communication Rate You set the communication rate switches the same for both the revisions A G and H modules Bits per Set switch second as L pw pee ON OFF OFF 600 OFF ON OFF m pw o or sw por por or ms pow oro sw poro o wm wj NOTE Any switch settings not shown above will give a communication rate of 9 600 bits per second Parity You can set parity switches only if you hae revision A G module If you want your module to have mmy Diagnostic Commands To set diagnostic commands for revision A G modules refer to the table in the section titled Diagnostic Commands If you want your module to execute dignostic commands pass through ddiagnostic ccommands Chapter 3 Installation Replacing a 1771 KC KD Module with a KE KF Module By setting the switches properly on the KE KF module you can use it to replace an older 1771 KC KD module in an
88. T and SRC The DST destination byte contains the station number of the station that is the ultimate destination of the message The SRC source byte is the station number of the station that originated the message The network layer supplies the DST and SRC values Allowed values for these bytes are 0 to 254 decimal Note that you can form the DST and SRC bytes of a reply message simply by interchanging the DST and SRC bytes of the corresponding command message CMD and FNC The CMD command and FNC function bytes together define the activity to be performed by the command message at the destination station CMD defines the command type and FNC if used defines the specific function under that command type Appendix A lists all the available CMD and FNC codes in hexadecimal notation The exact format for a particular message depends on the CMD and FNC values Section titled Message Packet explains the use of each command or function and gives a detailed description of the message text format for each Figure 5 4 shows the format for the CMD byte itself Bits 0 through 4 contain the command code Bits 4 and 7 should always be set to 0 Bit 5 is the priority indicator set it to 0 for normal priority messages and 1 for high priority messages chapter 2 Bit 6 is the command reply indicator set it to 0 in a command message and 1 in a reply message 54 Chapter 5 Message Packet Formats Note that reply messages also con
89. TS Where the extended status byte is optional Set To Run Mode This command sets the selected controller to Run mode Command Format 0E 02 sel Reply Format A Format when successful execution 4E Format when reporting an error 4E STS Where the extended status byte is optional Set To Single Scan Test Mode This command sets the selected controller to Single Step Test mode Command Format 04 sel 5 41 Chapter 5 Message Packet Formats 5 42 Reply Format A Format when successful execution oleae B Format when reporting an error Te Tele er 4E STS Where the extended status byte is optional Set To Test Mode This command sets the select controller to Test mode Command Format 0E 03 sel Reply Format A Format when successful execution Cono B Format when reporting an error onune 4E STS Where the extended status byte is optional General Data Encoding Data Manipulation This chapter explains two areas of special concern when you are transmitting messages between computers and PC s Data encoding Addressing formats This information contained in this chapter gives some application details that relate to the data and address fields of the message formats described in chapter 5 In general PC store binary data 1s and Os in 16 bit groups called words If you are looking at this data from a computer however you may interpret it in a number of different
90. UPT Subroutine TRANSMIT INTERRUPT NOTE This figure assumes the use of 280 510 NOTE UART transmit interrupt must be enabled and disabled without affecting the current state of the receive status interrupt flags enable WAKEUP Resume es eepin TXWAT INTERRUPT RETURN 11179 1 B 16 Figure B 18 SLEEP AND WAKEUP Subroutines SLEEP An Implementation Dependent Routine to Suspend Own Process at a Sleep Variable Until Another Process Wakes This One UP C RETURN WAKEUP An Implementation Dependent Routine to Wake Up the Process at a Sleep Variable if Any is Sleeping There RETURN Appendix B Detailed Flow Charts Input The Address of a Sleep Variable Sleep Variables Typically an address of a stack or a process or context save area e A Process can suspend itself and place its address in a sleep variable e Subsequently another process can wake up the sleeping process by referring to sleep variable When no process is sleeping at a sleep variable a WAKEUP has no effect Input The Address of a Sleep Variable 11180 1 B 17 Appendix B Detailed Flow Charts NOTE SLEEP and WAKEUP are always used in connection with some type of indivisible interprocess interlock Indivisibly is achieved on many processors e g Z 80 by disabling processor interrupts For this reason SLEEP and WAKEUP assume that interr
91. VG 4 Receiving O RDY lt Message Ready lt Computer Link Active CPU lt RS 232 C Channel Communcation Error o o 3 27 General Definition of Link Protocol RS 232 C Link Protocols This chapter describes the communication protocol used on the RS 232 C link to the KE KF module If you are connecting a KE KF module to another Allen Bradley communication interface module such as a 1771 KG 1773 KA or 1775 KA module then you need not be concerned with protocol because the modules automatically take care of it However if you are connecting a KE KF module to a computer then you must program the computer to understand and to issue the proper protocol character sequences as described in chapters 4 through 6 of this manual A link consists of a wire and associated hardware such as transceivers UARTs and error checkers A link protocol carries a message error free from one end of the link to the other or it indicates failure with an error code Internally it delimits messages detects and signals errors retries after errors and controls message flow It requires that the link hardware send characters from one end of the wire to the other The only purpose of a link protocol is to carry a message intact over a link It has no concern for the content of the message the message s function in the operation of higher levels in the system or the ultimate fate or purpose o
92. a poll when they have no messages to send Link Layer Packets Half duplex protocol uses three types of transmissions Polling packet Master message packet Slave message packet The master station transmits both polling packets and master message packets while slave stations transmit slave message packets Figure 4 14 illustrates the formats of these packets Note that the slave message packet has the same format as the full duplex message packet section titled 4 22 Chapter 4 RS 232 C Link Protocol Link Layer Message Packets The master message packet is the same as the slave message packet except that it is prefixed with DLE SOH and an address code to specify a slave station number At the end of each polling packet there is a BCC byte At the end of each message packet there is either a one byte BCC field or a two byte CRC field With a series A G module you must use BCC With series H module you can select BCC or CRC through switch settings Block Check The block check character BCC is a means of checking the accuracy of each packet transmission It is the 2 s complement of the 8 bit sum modulo 256 arithmetic sum of the slave station number STN and all the data bytes in the packet For polling packets the BCC is simply the 2 s complement of STN The BCC does not include any other message packets codes or response codes 4 23 Chapter 4 RS 232 C Link Protocol Figure 4 14 Formats for Hal
93. able industrial terminal communication Command Format 07 05 Reply Format Berges 5 25 Chapter 5 Message Packet Formats 5 26 Physical Read This command reads bytes of data from the PC data table or program memory Use this command to upload the contents of PLC 2 memory to your computer Use the SIZE field to specify the number of bytes to be read To specify a number of PC words SIZE should be an even value because PC words are two bytes long Command Format connie Reply Format meee 44 N Physical Write This command writes bytes of data into the PC data table or program memory Use this command to download the contents of a computer file into PLC 2 memory Use the SIZE field to specify the number of bytes to be written To specify a number of PC words SIZE should be an even value because PC words are two bytes long Command Format E ADDR DATA Max of 243 bytes N Reply Format Gorge Chapter 5 Message Packet Formats Set Data Table Size This command sets the data table size for the PLC 2 processor Use this command immediately before performing any physical writes on the PLC 2 processor For the DATA field in this command enter the number of bytes of memory that you want to allocate to the PLC 2 data table Since PC words are two bytes long the DATA value is double the number of words in the PLC 2 data table The DATA value is also equivalent to the physi
94. accept all messages regardless of duplication Refer to chapter 4 if you need a description of duplicate messages Handshaking Signals Switch 4 determines whether the module uses and recognizes the following handshaking signals data set ready request to send clear to send data carrier detect and data terminal ready If you want the module s RS 232 C port to set switch 4 use handshaking signals on ignore handshaking signals Diagnostic Commands Switch 5 determines how the KE KF module treats diagnostic commands sent to it by aremote Data Highway station You can connect the RS 232 C port of the KE KF module directly to a 1771 KG 1773 KA or 1775 KA communications interface module Figure 1 2 In such applications you can set switch 5 so that the KE KF module will either execute any received diagnostic commands itself or else pass those commands to the other attached communication module If you want your module to EDEN execute any received execute any received diagnostic commands commands pass any received Se command to the RS 232 C device Chapter 3 Installation Note that switch 5 relates only to diagnostic commands sent to the KE KF module from a remote Data Highway station Since only computers can transmit diagnostic commands the remote station must be a computer connected to the Data Highway by means of another KE KF module At the computer station the setting of swit
95. age low byte first In binary format ADDR would look like ADDR First Byte Second Byte ofofifofofofofo Low Byte High Byte value 20 hex value 00 Hex NOTE PLC and PLC 2 family controllers use this same logical addressing format when they transmit command messages to another station If you plan to transmit a command message to your computer from one of these PCs you should set up a buffer space in your computer to simulate PC memory You would then have to write computer application programs to accept and execute commands from the PC stations and to translate the ADDR value into the corresponding address in the simulated PC memory PLC 3 PLC 3 controllers use a form of logical addressing known as extended addressing With extended addressing you specify the address of each level or subdivision of PLC 3 memory down to the smallest subdivision you want to access You can use this method to specify up to 6 levels of PLC 3 extended addressing which is enough to give the address of a particular word in PLC 3 memory To send a command message to a PLC 3 station you would put the extended address in the field labeled PLC 3 extended addr in the message block formats chapter 5 Figure 6 7 shows an example of how to enter a PLC 3 extended address in this message field The first byte in the extended address field is a set of bit flags that indicate which addressing levels are specified in the bytes following the bit fl
96. ags If a flag bit is set to 1 the address bytes must contain a specification for the corresponding level of the extended address If a flag bit is zero the address bytes should not contain a specification for that addressing level instead a default value is assumed For Level The default address is 1 3 data table 2 Current context All others 0 PLC 3 Extended Address Logical Addressing Format Byte 1 Byte 2 Byte 3 Byte 4 Byte 5 Byte 6 Chapter 6 Data Manipulation You must always specify the value for the last level of the desired extended address even if it is the default value If the address values can be specified in one byte each then you can code the values directly If it takes two bytes to specify an address then you must use a delimiter byte of value FF hex before each 2 byte address Any 2 byte value should be encoded low byte first Figure 6 7 Example of PLC 3 Logical Addressing Format Level 1 Level 2 Level 3 Level 4 Level 5 Level 6 1 2 0 260 0 2 A Always zero dcs Byte 1 Byte 2 Byte 3 Byte 4 Byte 5 Byte 6 Flag bit for level Level 1 Default 3 for date table Level 2 Default 1 for current context Level 3 Value 2 Level 4 Default 0 Level 5 Value 260 6 5 4 3 2 00110110 1 1 1 1 1 1 1 1 0 0 0 0 0 1 0 0
97. ally to transmitter B receiver A and paths 3 and 4 There are actually two independent instances of the protocol operating simultaneously For simplicity the protocol will be defined on the subsystem that carries messages for A to B with reference to Figure 4 5 Although the protocols on each subsystem operate independently of each other there will be a slight interaction as transmission of a message is delayed when a two character response code is inserted in a stream of message codes Also any hardware problem that affects message codes traveling over a hardware circuit will also likely affect response codes on the same circuit 4 5 Chapter 4 RS 232 C Link Protocol Figure 4 3 Software Implementation of Data Paths Transmitter A Path 1 Path 2 Physical Circuit AB Receiver B Path 2 Path 1 Physical Circuit BA Path 3 Path 4 Receiver A Software Multiplexer Software Separator jus Path 3 Path 4 Transmitter B Path 1 Unrelated Parts of Figure 4 2 removed Figure 4 4 Transmitter A Path 1 M 11127 1 Receiver B Physical Circuit AB Path 1 4 6 11128 1 Chapter 4 RS 232 C Link Protocol Figure 4 5 Message Transmission from A to B Transmitter Receiver A B Path 2 Path 1 Path 1 Path 1 Path 2 s 11130 1
98. and on a Data Highway network or a stand alone link Read Write Diagnostic Mode select Reads There are two types of read Physical Unprotected A physical read allows you to read any area of PC memory at a remote station However a PC processor cannot originate a physical read command only a computer can originate a physical read An unprotected read can access only the data table area of PC memory Both computers and PCs can initiate unprotected reads Any read can request up to 122 words of contiguous data from PC memory Chapter 2 Communication Concepts Writes We can classify write commands both by their application and by their level of memory access As an application issue writes are divided between bit writes and word writes Bit writes allow the local station to control bits in the data table of a remote station Word writes allow the local station to write up to 121 contiguous words of data into the remote station s memory provided you abide by the restriction on memory access discussed next As with reads writes also are classified by the level of access to PC memory Non physical writes can access only the data table at a remote PC physical writes can access all of user memory including PC program memory Non physical writes can be further subdivided into protected and unprotected Protected writes can access only specified areas of the remote PC s data table memory The a
99. aracter oriented protocol that uses the following ASCII control characters extended to eight bits by adding a zero for bit 7 See ANSI X3 4 CCITT or ISO 646 for the standard definition of these characters Abbreviation Hexadecimal Code STX 02 ETX 03 ENQ 05 ACK 06 DLE 10 NAK 15 The term code is defined for use in the following paragraphs as an indivisible sequence of one or more bytes having a specific meaning to the link protocol Indivisible means that the component characters of a code must be sent one after another with no other characters between them It does not refer to the timing of the characters The following codes are used in full duplex protocol Control Codes DLE STX DLE ETX BCC CRC DLE ACK DLE NAK DLE ENQ Data Codes DATA single characters having values 00 OF and 11 FF DLE DLE to represent the data 10 4 2 Chapter 4 RS 232 C Link Protocol Codes can be grouped into two classes message codes which are sent from the transmitter to the receiver and response codes which are sent from the receiver to the transmitter DLE STX is a message code used to indicate the start of a message DLE ETX BCC CRC is a message code used to terminate a message DATA 00 0F and 11 FF are message codes used to encode the corresponding values in the message itself DLE DLE is a message code used to encode the occurrence of the value 10 hex in the message DLE ACK a response code signals
100. arly susceptible to this error stations 36 76 and 176 for example These numbers will depend on highway configurations Transmitted messages A 16 bit counter that records the number of messages successfully transmitted Received messages A 16 bit counter that records the number of messages successfully received MODEM CHANNEL COUNTERS 21 22 23 24 25 26 27 28 29 30 31 32 16 bit count of the number of times the station attempted to send message 16 bit count of the number of messages that were successfully transmitted and ACKed 16 bit count of the number of ACKs that were received Number of ACKs successfully passed from the receiver s separator to the transmitter Number of NAKs received Number of NAKs passed from the separator to the transmitter Number of timeouts waiting for a response Number of ENQs sent Number of messages that could not be successfully sent 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 7 Error Reporting Number of reply messages that could not be forwarded and which were destroyed 16 bit count of messages received 16 bit count of ACKs sent Number of NAKs sent Number of ENQs received Number of retransmissions received and ACKed Retransmission is a message that has a transparent word command and source
101. ate message if switch 1 of switch group SW 1 is on 11137 1 447 Chapter 4 RS 232 C Link Protocol Figure 4 13 Message Transfer with Message Sink Full SOURCE XMTR LINK RCVR SINK Data DLE STX Data DLE ETX Ful DLE NAK DLE STX Data DLE ETX Ful DLE ACK DLE STX Data DLE ETX Not Full Data gt ACK 11138 1 Examples If a line monitor were connected to the wires between station A and B and only the A to B subsystem were active the following would be observed Normal message Path 1 DLE STX DLE ETX BCCDLE STX DLE ETX BCC Path 2 DLE ACK DLE ACK Message with parity or BCC error and recovery Path 1 DLESTX XXX DLE ETX DLE STX DLE ETX BCC Path 2 DLE NAK DLE ACK Message with ETX destroyed 4 18 Half Duplex Protocol Chapter 4 RS 232 C Link Protocol Path 1 DLE STX XXXX timeout DLE DLE STX DLE ETX BCC Path2 DLENAK DLEACK Good message but ACK destroyed Path 1 DLE STX DLE ETX BCC timeout DLE DLE STX etc 2 DLXXXCK DLE Messages being sent in both directions Path 1 DLE STX DLE ETX DLE STX DLEETX BCC DLE STX Path 2 DLE DLE ACK Path 3 DLE STX DLEETX BCC DLE STX Path 4 DLE ACK Combined Circuit AB DLE STX DLE ETX BCC DLE STX DLE ETX BCC DLE ACK
102. atus information in a reply message This field is used only if the STS value if FO hex 3 PACKET OFFSET contains the word offset between the DATA field of the current message packet and the DATA field of the first packet in the transaction This offset value appears only in command messages for file transfers where the complete transaction might require more than one command or reply message packet The value of PACKET OFFSET is Zero for the first packet in a transaction 4 PLC 3LOGICAL ADDRESS contains the logical address of a PLC 3 file or word Chapter 6 gives more details about the contents of the address field 5 PLC 3 PHYSICAL ADDRESS contains the logical address of a PLC 3 file or word Chapter 6 gives more details about the contents of this address field 6 TOTAL TRANS contains the total number of data words transferred by the current transaction This is the total number of PLC 3 words to be transferred in the DATA fields of all message packets in the current transaction TOTAL TRANS appears only in command messages for file transfers where the transaction might take more than one message packet to complete 7 W E is the word file symbolic address flag This one byte flag specifies whether the symbolic address field following it represents a word address The value of W F is zero if the symbol represents a word address and non zero if the symbol represents a file address 8 WORD OFFSET contains the word offset
103. being used tis desirable to sacrifice throughput in exchange for ease of implementation Half duplex protocol requires the following communication characteristics 8 bits per character Even parity 1 stop bit Pass all mode the terminal driver does not translate or respond to control characters Single character buffer the terminal driver immediately returns each character to the caller Multidrop Topology The intended environment for half duplex protocol is a multidrop link with all stations interfaced through half duplex modems The actual nature of the link does not matter much as long as the modems support request to send clear to send and data carrier detect If dial up modems are used they must also support data set ready and data terminal ready otherwise DSR should be jumpered to DTR There may be from 2 to 256 stations simultaneously connected to a single link Each station has a receiver permanently connected to the circuit and a transmitter that may be enabled or disabled by RTS One station is designated as master and controls which station has access to the link Since Allen Bradley currently does not supply the master station this function must be performed by your own programmed intelligent device All other stations are called slaves and must wait for permission from the master before transmitting Each slave station has a unique station number from 0 to 254 The master can send and receive messag
104. ber of timeouts waiting for a response 10 Number of ENQs sent 11 Number of messages that could not be successfully sent 12 Number of reply messages that could not be forwarded and which were destroyed 13 16 bit count of messages received 14 15 16 bit count of ACKs sent 16 17 Number of NAKs sent 18 Number of ENQs received 19 Number of retransmissions received and ACKed A retransmission is a message that has a transparent word command and source that match the previous message 7 30 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 Chapter 7 Error Reporting Number of STX full duplex mode or SOH half duplex mode received This is in effect a count of the number of messages that were started Number of messages characters or message fragments that were ignored Number of messages that were aborted by receipt of a DLE ENQ Number of messages that were aborted by the receipt of an unexpected control code other than DLE ENQ Number of times the DLE ACK response was delayed because of a lack of buffer space for the next message Number of times the reply was changed from ACK to NAK because unexpected characters any besides DLE ENQ were received while waiting for memory to free up Number of broadcast messages received Number of broadcast messages that were successfully received Number of messages seen that were not for thi
105. cal address chapter 6 of the start of the processor s program memory To determine allowable data table sizes refer to the programming manual for the appropriate PLC 2 processor Command Format Te Tele eiTe 06 08 Reply Format Gore PLC 3 Commands PLC 3 stations can execute all of the commands in the basic command set They can also execute the following commands which apply only to PLC 3 controllers Non privileged Commands Bit write File read File write Word range read Word range write Privileged Commands Download request Physical read a Physical write Restart request Shutdown request Upload request Only a computer can initiate privileged commands Their primary use is for uploading and downloading PLC 3 memory 5 27 Chapter 5 Message Packet Formats Only a computer or another PLC 3 station can initiate the non privileged PLC 3 commands listed above Their primary use is for transferring data between two PLC 3 files Those files may be located in the same PLC 3 processor or in two different PLC 3 s In addition to the message packet fields already described for the basic command set section titled Message Packet PLC 3 messages may also contain the following fields 1 ASCII SYMBOL contains the ASCII codes for the characters in a PLC 3 symbolic address Chapter 6 gives more information on the format of symbolic addresses 2 EXT STS contains extended st
106. ccessible areas are defined by memory protection rungs in the remote PC s ladder diagram program Unprotected writes on the other hand can access any area of the remote PC s data table In most cases switch settings on the remote station s interface module can disable the module from executing each of these types of write commands Diagnostics Diagnostic commands have to originate from a device other than a PC You can use these commands to return status information from a remote or local station or to alter some onboard parameters at a station interface module Diagnostic commands are particularly useful during a startup or during on line debugging Mode Select Mode select commands allow you to load a new PC program from a remote computer station The operation of these commands varies by PC processor type These commands can be issued only by a computer Network Management Layer The network management layer is concerned with the specifics of conveying a message safely from its source to its destination This layer is the same for both RS 232 C and Data Highway links If your physical link contains only Allen Bradley PCs you do not have to program anything for this layer the communication interface modules automatically take care of it If your physical link contains a computer then 2 11 Chapter 2 Communication Concepts 2 12 refer to chapter 5 for a description of how to program this layer at the computer
107. ceived the BCC and the message buffer are reset and the receiver starts building a message While building a message all data codes are stored in the message buffer and added to the BCC If the buffer overflows the receiver continues summing the BCC but the data is discarded If a parity overrun framing or modem handshaking error is detected it is recorded If any control codes other than DLE ETX BCC is received the message is aborted and a DLE NAK sent on 4 11 Chapter 4 RS 232 C Link Protocol 4 12 path 2 When the DLE ETX BCC is received the error flag the BCC the message size and the address optionally are all checked If any of the tests fail a DLE NAK is sent on path 2 If the message is OK its header is compared to the last message If it is the same the message is discarded and a DLE ACK is sent Duplicate message detection is not implemented if switch 3 of switch group SW 1 is turned off If the message is different from the last one the state of the message sink is tested If the message sink is full a DLE NAK is sent otherwise the message is forwarded to the message sink the header information is saved for the duplicate message detector and a DLE ACK is sent The procedure for the 17871 KC KD and 1771 KG Rev C modules is different First the check the message sink state If the sink is full the response is recorded but not sent The receiver waits for a DLE ENQ on path 1 If any other code is rec
108. ch 5 does not affect any diagnostic commands that the computer sends to its local KE KF module The local module always retransmits the command message over the Data Highway without executing it Figure 3 3 illustrates these concepts Also note that you can have more than one computer station on a Data Highway and one computer can transmit diagnostic commands to the others At the receiving computer station if switch 5 is off the local KE KF module will pass the diagnostic commands to the computer In such cases you will have to write computer application programs to handle those commands at the receiving station If switch 5 is on at the receiving station the local KE KF module itself will execute the incoming diagnostic commands What to do next Now skip to section titled Station Number to learn how to set station numbers RS 232 C Link Features Revision H The following table shows you how to set the RS 232 C link features for revision H module switch numbers 1 2 5 with with If you want to parity embedded select protocol as 5 responses full duplex full duplex full duplex full duplex half duplex BCC none half duplex full duplex none half duplex CRC none 3 5 Chapter 3 Installation Figure 3 3 Effect of Switch 5 on Diagnostic Commands Computer Diagnostic command 1771 KF module Computer Reply message
109. command to the corresponding reply message Note that the low byte least significant bits of your TNS value will be transmitted across the link before the high byte most significant bits At any instant the combination of SRC CMD RNG and SQN are sufficient to uniquely identify every message packet in transit At least one of these fields in the current message must be different than the corresponding field in the last message received by a command executor If none of these fields is different the command executor ignores the current received message This process is called duplicate message detection ADDR The ADDR address field is a 2 byte field that contains the address of a memory location in the command executor ADDR specifies the address where the command is to begin executing For example if the command is to read data from the command executor ADDR specifies the address of the first byte of data to be read The first byte of the ADDR field contains the low least significant byte of the address and the second byte of ADDR contains the high byte of the address Chapter 6 gives more details on the contents of the ADDR field Note that the ADDR field specifies a byte address not a word address as in PC programming Chapter 6 explains how to convert PC word addresses to byte addresses SIZE The SIZE byte specifies the number of data bytes to be transferred by a message This field appears in read commands where it s
110. coupled modems The connection is established by human operators at both ends who insert the handsets into couplers to complete the connection DTE controlled answer these unattended modems are directly connected to the phone lines The module serves as the data terminal equipment to control the modem via the DTR DSR and DCD signals The module incorporates timeouts and tests to properly operate these types of modems Auto answer these modems have self contained timeouts and tests and can answer and hang up the phone automatically The module has no means of controlling an auto dial modem but it can be used in conjunction with a separate auto dialer Connection to Another Communication Module To provide a longline RS 232 C communication link with a 1771 KG module refer to Figure 3 11 To provide a longline RS 232 C link with a 1773 KA or 1775 KA module refer to Figure 3 12 To construct the cable use a 15 pin male connector at each end Use Belden 8723 or equivalent cable available from Allen Bradley under cat no 1778 CR Connect the cable shield at one end only You may make the longline cable up to 7 000 feet long However remember that the cable length can limit the communication rate section titled Electrical Characteristics Answering The module continually asserts DTR when it is waiting for a call Under this condition the modem will answer a call and assert DSR as soon as it detects ringing The modul
111. cted if no command rungs have yet been detected and if the branch being processed started with a BST BST Branch Start BND Branch End 05 The address field of the first GET in a memory access branch contains an invalid Data Highway station address The address must be less than 377 06 The second element of a memory access branch is not a GET 07 The third element of a memory access branch is not a GET 08 Invalid window address in memory access branch the address in the second GET is greater than the third GET 7 3 Chapter 7 Error Reporting 7 4 09 There is something besides a BST or BND after the third GET of a memory access branch 10 There is something other than a BST or output instruction after BND in a Memory access rung 11 A rung in the communication zone starts with something besides a BST or an XIC or the zone contains no command rungs and the terminating rung has been omitted 12 The start bit address specified for a command rung is in the low byte of a word Start bits must always be in the 10 to 17 range 13 The second element of a command rung is not an XIC 14 The command code the low digit of the address of the second XIC in a command rung is invalid 15 The station address in the second XIC of a command rung is invalid Station address must be less than 377 16 An instruction or an opcode other than XIC XIO BST or BND has been encountered in a bit control comman
112. d it is included in the value in the register the same way After the ETX value is included in the value in the register and is transmitted the value in the register is transmitted right bit first as the CRC field The receiver also calculates the CRC value and compares it to the received CRC value to verify the accuracy of the data received NOTE In half duplex mode there is a BCC on the polling packet regardless of whether BCC or CRC error checking is used on messages Protocol Environment Definition In each station there is a program connected to the link hardware that is called the transceiver The master station has a more complex transceiver than the slaves since it must include a polling algorithm Only the slave s transceiver is defined here as illustrated in Figure 4 15 Chapter 4 RS 232 C Link Protocol To fully define the environment of the protocol the transceiver needs to know where to get the messages it sends and must have a means of disposing of messages it receives These are implementation dependent functions that shall respectively be called the message source and the message sink We assume that the message source will supply one message at a time upon request from the transceiver and will require notification of the success or failure of transfer before supplying the next message Whenever the transceiver has received a message successfully it will attempt to give it to the message sink The
113. d be ADDR First Byte Second Byte 9191110 z z 8 5 2 5 oO Chapter 6 Binary Codes for PLC 4 Logical Addresses Table 6 A Binary Code d 1 d 2 d 3 d 4 d 5 d 6 d 7 or iI iI I PLC 4 Data Table Location 1 2 i i7 i7 i o I O Flags Word 1 I O Flags Word 2 I O Flags Word 3 I O Flags Word 4 I O Flags Area Unused X 4X X X X S S S S S S S Qadqaaaaaadaaadnadnaanadnaanaanaanananand Qaqaqaaoaaadadaadaaaaaaadnadnaanadnandnandnandnandtand C C C C C C C C C C C C C C C CO OB OO O0 0 0 O0 O0 O0 O0 O0 O0 O0T dOc d0 cT oor roor roor roor roor roor roor OO QO O0O0O0 O0 T Y OO O00 0o Oo OD 0cooocococcoocos Or c C c T T oc oc oc oc o o 0 o Co CQ Q Q Q Q Q Q QO O QO O QO Or
114. d on the received data and checks this against the CRC value included with the received message A discrepancy between the transmitted CRC and the CRC computed by the receiving station indicates some fault in the transmission If the received and computed CRC values do not agree the message is not accepted as valid Link Disconnect Floating master operation continues normally as long as all stations hare mastership of the Data Highway link However if any one station retained continuous control of the communication link due to a fault condition floating master operation would not be possible and Data Highway communication would be disabled As a preventive measure against this type of situation each station interface module has automatic link disconnect circuitry If a module detects that it is not relinquishing mastership of the Data Highway this circuitry can disconnect the module from the Data Highway link The other stations on the Data Highway can then continue to function normally General Communication Option Switches Installation This chapter explains how to install the 1771 KE and 1771 KF modules There are five parts to installation Setting the communication option switches Mounting the module Connecting the module to its power supply Connecting the module to the Data Highway and RS 232 C links Observing the diagnostic indicators Please read the first three chapters of this manual carefully before atte
115. d rung or the output element of the rung is incorrect 17 The third element of a read or write command rung is not a GET 18 The fourth element of a read or write command rung is not a GET 19 The fifth element of a read or write command rung is not a GET 20 The sixth element of a read or write command rung is not a legal output instruction 21 The start of a command rung is not an XIC or the terminating rung has been omitted This error is only generated if valid command rungs precede it 22 The word containing start done error bits is positioned so that it crosses a boundary in the data table For example start bit 07710 means that the error bits would be in word 100 or 17710 means that the error bits would be located in the first word of the program 23 An unprotected write or bit control command is specified and the DIP switch that enables sending of unprotected commands is off 24 Not used in 1771 KA 25 Not used in 1771 KA Chapter 7 Error Reporting 26 Too many command rungs A maximum of 255 command rungs can be programmed 27 The default timeout is too large Valid timeouts are from 011 to 407 octal The value 010 causes the timeout to be disabled 30 A command rung syntax error has been detected in RUN mode after the pre scan This means that either the communication zone has been altered by online editing hardware problems or a highway download operation or that it has been moved by a gap or
116. de a useful tool for diagnosing problems if a troubleshooter has available a device that will read the internal error counters of module the ACK timeout counter and the false poll counter will be useful for diagnosing bad cabling or a noisy or loaded highway installation Also useful is the ratio of messages transmitted successfully returned an ACK from the remote station versus the commands sent but not necessarily completed NOTE Because of differences in revision levels in a given module and variations from module to module the user must first request the location of these counters by transmitting to the module a diagnostic status command Then based on the address returned the number of the following counters can be used as an offset to calculate the location of the desired counter or to calculate how many counter values he wants returned This information is then used to format a diagnostic read command and the reply from that will contain the data stored in the counters Also the counters are divided into two categories Data Highway and RS 232 and they apply to activity on their respective parts Obviously the 1771 KA will only have Data Highway counters Most modules will have both The second section lists internal error counters bytes of information stored in RAM in each Data Highway module These numbers can only be read by issuing a diagnostic read command from a device connected to one of the modules that supports an RS 232
117. des are unused because of holes in the address space of PLC 2 family products 0 to 7 and 100 to 107 octal Reads or writes to these codes will be rejected in error These addresses are illegal for Bit Write commands DON T bits This is a bit pattern that selects the desired controller in the PLC 4 Microtrol loop 000 selects controller 1 001 selects controller 2 etc Selects high byte when 1 low byte when zero Physical Addressing Physical addressing is the type of addressing a computer would use to send a privileged command to a PC station In particular you would use physical addressing to upload or download PC memory The recommended procedure for doing this is to use a series of physical read or write commands that begin at physical address 0000 and proceed sequentially to the end of PC memory 6 12 Bit Number Octal Logical Byte Address Physical Byte Address Chapter 6 Data Manipulation Because of the differences in PC memory organization the physical addressing scheme varies somewhat with controller type PLC PLC controllers use physical addresses that are exactly the same values as the corresponding logical addresses Remember that the logical address is a byte address so the physical address will also be a byte address For example the logical byte address of the 17th word in PLC memory is 32 decimal and the physical address of the word is also 32 decimal To send a ph
118. e 6 Waits no receive buffer space at destination station 7 Timed out master failed 8 False polls failure to transfer 9 Received acknowledgment when not master 10 Message size too small less than 5 bytes 1l Incorrect DST or SRC DST 12 Memory not available for receive buffer 13 Received message has bad CRC value 14 Message too long 15 Message arrived when no buffer space left 16 Retransmissions of previously received message 17 Aborts result of line noise 18 Messages successfully transmitted 19 Messages successfully transmitted 20 Messages successfully received 21 Messages successfully received 22 Command messages sent 23 Command messages sent 7 33 Chapter 7 Error Reporting 24 Reply messages received 25 Reply messages received 26 Command messages received 27 Command messages received 28 Reply messages sent 29 Reply messages sent MODEM PORT 1 Command messages sent 2 Command messages sent 3 Reply messages received 4 Reply messages received 5 Command messages received 6 Command messages received 7 Reply messages sent 8 Reply messages sent 9 ACKs received 10 ACKs received 11 ACKs sent 12 ACKs sent 13 NAKS received 14 NAKS received 15 NAKSs sent 16 NAKs sent 17 Undeliverable reply messages 18 Computer link timeout preset to 500 msec 19 Computer link timeout preset to 500 msec Transmissions Between Computer and Ful
119. e Message size too large Write privileges not granted to remote station A B Requesting station already has upload download access privileges 7 37 Chapter 7 Error Reporting Hex Value E Shutdown request could not be executed F Requesting station does not have upload download access privileges 7 38 Switch Settings Appendix Switch Settings Here is a reference for switch settings for a 1771 KE KF communication controller module Prior to revision H Switch Assembly SW 1 Switch 1 Switch 2 Switch 3 Switch 4 Switch 5 Off Full Duplex On Half duplex Off Embedded response disabled On Embedded response enabled Off Duplicate message detection disabled On Duplicate message detection enabled Off RS 232 C handshaking disabled On RS 232 C handshaking enabled Off Remote diagnostics pass through On Remote diagnostics enabled A 1 Appendix A Switch Settings Here is a reference for switch settings for a 1771 KE KF communication controller module Revision H with If you want to i embedded select protocol as responses full duplex uae RG wm _ If you want the module to use handshaking signals ignore handshaking signals If you want the module s RS 232 C port to set switch 4 detect and ignore duplicate messages on accept all messages regardless of duplication 2 Appendix A Switch Settings
120. e does not monitor the RING indicator in the RS 232 interface Once it detects DSR the module starts a timer around 10 seconds and waits for the DCD signal When the module detects DCD communication can start 3 23 Chapter 3 Installation If the module does not detect DCD within the timeout the module turns DTR off This causes the modem to hang up and break the connection When the hang up is complete the modem turns off DSR This causes the module to reassert the DTR line and wait for another call This feature protects access to the phone if someone calling a wrong number reaches this station Figure 3 11 Connection to 1771 KG Module User Supplied Male Connectors User Supplied Cable RS 232 C Belden 8723 or Equivalent d RS 232 C PORT Connector 7000 Ft Max PORT Connector of KE KF Cat No 1778 CR of 1771 KG Module y Module f 15 Pin Male 15 Pin Male Connector Connector a Connection Diagram 15 Pin Male 15 Pin Male Connector Connect the Shield Connector X at One End Only RS 232 C RS 232 C 1 L L 1 PORT Connector PORT Connector of 1771 KG of KE KF 2 3 Module Module 14 25 3 2 13 7 NA yy 4 4 User Supplied Cable 5 Belden 8723 or Equivalent 5 7000 Ft Max 6 6 8 8 11 20 a User Supplied Male Connectors j b Wiri
121. e modules that work together to provide a channel for communication between the various points called stations on the physical link A station consists of an intelligent programmable device e g PC or computer and the module or modules that interface it with the physical link 2 1 Chapter 2 Communication Concepts 2 2 In this way the KE KF module allows stations on one link to communicate with stations on the other link Since these two physical links have different communication protocols the KE KF module serves mainly as a protocol translator Data Highway The Data Highway is a local area network LAN that can allow peer to peer communication among 64 stations Figure 2 1 illustrates a Data Highway network The Data Highway link consists of a trunkline that can be up to 10 0900 feet long and droplines that can be up to 100 feet each Each station is at the end of a dropline The Data Highway link implements peer to peer communication through a modified token passing scheme called the floating master With this arrangement each station has equal access to become the master The stations bid for temporary mastership based on their need to send information Unlike a master slave relationship a floating master relationship does not require the current master to poll each station to grant permission to transmit Therefore it provides a more efficient network because there is less overhead per transaction Stations
122. e scan Errors These are mostly communication zone syntax errors They are numbered 1 to 29 They are detected as the KA module pre scans the communication zone just before it starts scanning start bits Note that no syntax errors are detected in the header rung If the pre scanner does not recognize the header rung it will decide that it is not a header rung and will continue scanning until the end of memory or until it finds a valid header rung Pre scan errors always cause the module to turn on the PROG light and enter an error state When the keylock is turned to PROGRAM the error state is exited and the PROG light turned off For all pre scan errors the upper two digits act as a pointer to the rung containing the error Rungs are numbered from 1 to 99 then wrap around back to 0 through 99 and so on The first rung after the header rung is number 1 If no pre scan error is detected the error code word is set to all zeros at the end of the pre scan Runtime Errors For all runtime errors the first two digits of the code are a modulo 100 error counter The first error is number 1 Except as noted the module continues operating after recovering from a runtime error Chapter 7 Error Reporting Runtime errors are divided into the following groups 1 Message formatting numbered from 30 to 39 They are detected as a message is being formatted and before it is sent A few of these errors result in the KA turning on the PROG li
123. ected because the header was incomplete This should only be counted because of undebugged software or in the unlikely event that a bad frame fooled the CRC checker Wrong destination address Counts the number of frames that were rejected because the destination address was incorrect This can have the same cause as 8 This counter also detects frames that have the same source and destination address Receiver memory full Counts the number of times that the receiver sent an ACK without first being able to allocate a receiver buffer This will result in a memory overflow error when the next message is received 7 21 Chapter 7 Error Reporting 7 22 12 13 14 15 16 17 18 19 20 21 22 23 24 Bad frame status Counts the number of frames that were rejected because of a bad CRC This error is very common on a noisy highway Buffer overflow Counts the number of times a message was received that contained more than 250 bytes Memory overflow Counts the number of times a message was received when there was not buffer space allocated for it This usually follows a memory full error Retransmits Counts the number of duplicate frames received A duplicate frame is sent by a transmitter when it fails to receive an ACK If the reason it failed to receive an ACK was that the ACK was lost rather than because the original message was lost the duplicate is redundant and should be discarded
124. eived the response is changed from ACK to NAK and the receiver continues waiting for a DLE ENQ If a DLE ENQ is received the sink status 1s checked If it 1s still full the receiver continues waiting If it is not full the last response is sent and the receiver then accepts new messages This variation is not documented in the structured English section below The receiver for the KE KF module is listed below in structured English Figure 4 8 is a flowchart of the software logic for implementing the receiver Chapter 4 RS 232 C Link Protocol Figure 4 8 Receiver for Full Duplex Protocol C RCVE l LAST NAK Receive Yes DLE ENQ Receive Message BCC CRC OK No LAST NAK Yes LAST ACK Send DLE LAST 11133 1 4 13 Chapter 4 RS 232 C Link Protocol RECEIVER is defined as variables LAST HEADER IS 4 bytes copied out of the last good message RESPONSE is the value of the last ACK or NAK sent BCC is an 8 bit block check accumulator LAST HOLDER invalid LAST RESPONSE NAK loop reset parity error flag GET CODE if DLE STX then begin BCC 0 GET CODE while it is a data code begin if buffer is not overflowed put data in buffer GET CODE and if the control code is not a DLE EXT then send DLE NAK else if error flag is set then send DLE NAK else if BCC is not zero then send DLE NAK else if message
125. emote station Unless noted otherwise whether in a Data Highway link or an RS 232 C link the discussion will be limited to a single local station and a single remote station The network layer protocol distinguishes a command from a reply Obviously the data area of a command and its corresponding reply depends on the type of command Chapter 2 Communication Concepts 2 10 Priority Each message on a Data Highway link is classified as either High priority Normal priority The priority levels of messages determine the order in which stations are polled and allowed to transmit messages In the polling process stations with high priority messages will always be given priority over stations with normal priority messages You specify the priority level for each command message The command code contains this specification The station that receives a command message must establish the same priority level for its corresponding reply message NOTE Stations with high priority messages are given priority over stations with normal priority messages throughout the command reply message cycle For this reason a command should be given a high priority designation only when special handling of specific data is required Using an excessive number of high priority commands defeats the purpose of this feature and could delay or inhibit the transmission of normal priority messages Command Structures There are four basic types of comm
126. ensitive to problems on longer cables It will also show up often if the cable connections are loose 2 Contention Counts the number of times contention was detected This will also show up quickly on noisy or overlength cables This counter corresponds to error 93 3 Bad ACK status Counts the number of times the ACK was successfully received but contained a nonzero status code other than memory full 4 Returned messages Counts the number of times the highway driver returns a message to sender with a nonzero status code because a reply 7 23 Chapter 7 Error Reporting 7 24 10 12 was not received from a remote station Each count corresponds to one local error bit set or one reply message lost Transmit memory full Counts the number of times that the receiving station s memory was full Each time this happens the message is placed on a waiting queue for a half second Each message will be re tried five times for memory overflow before it is returned to sender Poll timeout Counts the number of times this station grabbed mastership of the highway because it timed out while waiting to hear a valid frame On a highway that has just been powered up there should be only one station that has this counter incremented False poll Counts the number of times that this station has tried to relinquish mastership and the station that was expected to take over failed to respond This happens often on a noisy highway
127. ent Routine that Removes a Message from a Queue RETURN Figure B 23 LINK Subroutine C LINK Appendix B Detailed Flow Charts Input e Address of Queue Output e Message Control Block 11184 1 Input e Address of Queue Message Block An Implementation Dependent Routine that Places a Message onto a Queue RETURN 11185 B 21 Appendix B Detailed Flow Charts Figure B 24 Receiver Routine for Full Duplex Protocol C RCVE Y Reset Buffer Flag Set Header to Illegal Value GET BUFFER Get a Buffer LAST Variables LAST Value of Last Response HEADER DST SRC CMD STS and TNS from last message BUFFER Whether an Empty Buffer is Read e Receiver error flag Reset Receiver Error Flag i GET CODE Get Next Input Control Code SEND CTL Transmit LAST XMSG Transfer Message to Network Layer Ignore Flag 0 No Save Response ACK or NACK in LAST B 22 NOTE XMSG Returns ACK NACK or 0 for Ignored Message 11186 1 Appendix B Detailed Flow Charts Figure B 25 XMSG Subroutine XMSG GETBUF Output Flag Check Availability ACK if M
128. epend on highway configurations Transmitted messages A 16 bit counter that records the number of messages successfully transmitted Received messages A 16 bit counter that records the number of messages successfully received Number of ACKs received No used Number of ACKs Not used Number of NAKs received Not used Number of NAKs sent Not used Undeliverable replies Counts the number of replies that were lost because they could not be delivered over the highway Undeliverable commands 7 25 Chapter 7 Error Reporting 7 26 30 31 32 can be signalled to the user because the user is located in PC memory and can always be reached If a reply message cannot be delivered over the highway there is no way to signal the user of that message who is also over the highway that this station cannot signal a reply The local user is not concerned with the problems of the remote user and can take no meaningful action anyway so there is not much to do but destroy the message and count it Timeout preset NAK preset Values set by diagnostic commands or set by default on power up ENQ preset 1771 KF Error Counters DATA HIGHWAY COUNTERS 0 Bad CRC or I O error on ACK Same causes as bad CRC on messages ACK timeout Counts the number of times that the sender timed out waiting for an acknowledgement This is a common error and will be one of the first to respond to reflections or low le
129. es from B to A At the same time transmitter B and receiver A carry out the transfer of messages from station B to station A by sending message packets from B to A and returning responses from A to B Figure 4 2 shows the four independent data paths involved 4 4 Chapter 4 RS 232 C Link Protocol Figure 4 2 Data Paths for Two Way Simultaneous Operation Path 1 Transmitter Receiver A B Receiver Transmitter A B 11126 1 Path 1 carries message codes from A to B path 2 carries response codes from B to A path 3 carries message codes from B to A and path 4 carries response codes from A to B To implement all these data paths with only two physical circuits a software multiplexer combines the message codes with the response codes going in the same direction At the other end of the link a software separator divides the message codes from the response codes The message codes are sent to the receiver and the response codes are sent to the transmitter via internal software On each physical circuit response codes from a receiver to a transmitter will be seen intermingled with message codes being sent from a transmitter to a receiver Figure 4 3 depicts this implementation Figure 4 4 shows path 1 with unrelated parts of Figure 4 3 removed Paths 2 3 and 4 could be similarly shown The full duplex protocol is symmetrical that is anything that can be said about transmitter A receiver B and paths 1 and 2 applies equ
130. es to and from each station on the multidrop The master can send and receive messages to and from every station on highways that are connected to the multidrop via a KE KF module If the master is programmed to relay messages then stations on the multidrop can Chapter 4 RS 232 C Link Protocol engage in peer to peer communications The multidrop will not easily provide flexible peer to peer communication between the multidrop and connected highways or between different highways Either a two circuit system master sends and slaves receive on one circuit slaves send and master receives on the other or a one circuit system master and slaves send and receive on the same circuit may be used Half duplex dialup modems can be used as long as a carrier is detected before the carrier timeout about 8 seconds If a carrier is not sensed before the timeout the module will hang up the phone Carrier must be sensed at least every 8 seconds to maintain the connection Multiple masters are not allowed except when one acts as a backup to the other and does not communicate unless the primary is shut down Transmission Codes Half duplex protocol is a character oriented protocol that uses the following ASCII control characters extended to 8 bits by adding a zero for bit 7 See ANSI X3 4 CCITT V 3 or ISO 646 for the standard definition of these characters Abbreviation Hexadecimal Code SOH 01 STX 02 ETX 03 EOT 04 ENQ 05 ACK 06 DLE 1
131. essage is OK of Receive Buffer NAK if Message is in Error Clear CRC 0 if Message is to be Ignored Was Buffer A Available GETCODE am Get a Code Buffer e Overflow Link Data No Message Too Small Code No Station No 2 Return An Buffer Ignore Flag 0 _ Available Compare Message eae with HEADER a NAK Duplicate Save Byte Message in Buffer i Save New Header GETCODE Get Next Code SENDNET Send Link Data to Yes GETBUF Try to Get A Return 4 US B 23 App endix B Detailed Flow Charts B 24 Figure B 26 GETCODE Subroutine GETCODE GETRAW Get Byte From UART GETRAW Get Byte From UART Save ACK or NAK in RESP TA WAKEUP Resume XMIT if Sleeping at WTRESP BCC No Add Data Byte to BCC Yes Return Byte and Data Flag GETRAW Get BCC BCC Include in Check Return EXT and Control Flag Return Byte and Control Flag Output BYTE What Was Received e Control Data Set if BYTE is a control character which was preceded by a DLE NOTE BCC Should Now Equal Zero 11188 1 Figure B 27 GETRAW Subroutine GETRAW Disable Processor Interrupts Set Receiver Error Flag Discard Bad Data Reset UART Error Flag Yes 1 Enable UART Receive Interrupt
132. f Duplex Protocol DLE ENQ STN BCC 8 Polling Packet From CMD STS FNC ADDR DATA Application Layer N N N N N N N N From Data DST SRC CMD STS ms From Application Layer pen NS d S 758 N P N P x Pd N P d rd N Be N m Data BCC DLE STX From Network Layer DLE ETX pee b Slave Message Link Packet From CMD STS FNC ADDR DATA Application Layer N N N N N N N X Data From DST SRC STS INS From Application Layer aoe Data DLE SOH STN DLE STX From Network Layer DLE ETX BOO 4 24 c Master Message Link Packet 11139 1 Chapter 4 RS 232 C Link Protocol For example if the master station wanted to send the data codes 8 9 6 0 2 4 and 3 to slave station 20 hex 40 octal the master message codes would be in hex 10 01 20 10 02 08 09 06 00 02 04 03 10 03 CO DLE SOH STN DLE STX Data DLE ETX BCC The sum of the STN and data bytes in this message packet is 40 hex The BCC is the 2 s complement of this sum or CO hex This is shown in the following binary calculation 0100 0000 hex 1011 1111 1s complement X41 1100 0000 25 complement hex To transmit the STN or data value 10 hex you must use the data code DLE DLE However only one o
133. f the message Once the message has been reliably carried from one end of the link to the other the link protocol s concern for that message is ended The RS 232 C port of the KE KF module can use one of two link protocols which are Full duplex protocol for point to point communication Half duplex protocol for master slave communication In general full duplex protocol gives faster data throughput but is harder to implement half duplex protocol is easier to implement but gives slower data throughput Each of these protocols is described independently in sections titled Pull Duplex Protocol and Half Duplex Protocol respectively NOTE Some Data Highway documentation might refer to full duplex and half duplex protocols as DF1 and polled mode protocols respectively 4 1 Chapter 4 RS 232 C Link Protocol Full Duplex Protocol The full duplex conforms closely to ANSI X3 28 combining features of subcategories D1 data transparency and F1 two way simultaneous transmission with embedded responses Full duplex protocol is used over a point to point link that allows two way simultaneous transmission It is relatively difficult to implement because it requires a system programmer to use interrupts and multi tasking techniques It is intended for high performance applications where it is necessary to get the highest possible throughput from the available medium Transmission Codes Full duplex protocol is a ch
134. f the bytes are DST destination station for the message 1 SRC source station of the message CMD command code STS status code TNS transaction a RNG rung number for PC command message SQN sequence number of message FNC function code ADDR address of memory location DATA data values being transferred by the message These bytes are described in more detail below Not all command messages have FNC ADDR or DATA bytes Figure 5 2 Command Message Packet Format From CMD STS FNC ADDR DATA Application x Layer x DST SRC STS ala eee icati ayer ie From Application Layer Basket Legend x low hex digit of CMD byte supplied by application layer iei 5 3 Chapter 5 Message Packet Formats Figure 5 3 shows the general format of a reply message Network layer fields are shaded The definitions of these bytes are the same as for command messages Not all reply messages have DATA bytes Figure 5 3 Reply Message Packet Format From CMD STS DATA Application x Layer Network Layer Packet Legend x low hex digit of CMD byte supplied by application layer 11152 1 Layer DST SRC CMD STS TNS Note that the bytes are shown from left to right in the order in which they are transmitted across the link DS
135. f these DLE text characters is included in the BCC sum For example to transmit the values 8 9 6 0 10 4 and 3 hex a slave station would use the following message codes Represents single text value of 10 10 02 08 09 06 00 10 10 04 03 10 03 D2 In this case the sum of the data bytes is 2E hex because only one DLE text code is included in the BCC So the BCC is D2 hex The BCC algorithm provides a medium level of data security It cannot detect transposition by bytes during transmission of a packet It also cannot detect the insertion or deletion of data values of zero within a packet Cyclic Redundancy Check Calculate the CRC value on the value of the data bytes and the ETX byte using the polynomial x16 x 2 0 To transmit the data value of 10 hex you must use the data code DLE DLE However only one of these DLE data bytes is included in the CRC value Embedded responses are not included in the CRC value At the start of a message packet the transmitter clears a 16 bit register for the CRC value As a byte is transmitted it is exclusive OR d with bit 0 to the right to the right eight bits of the register The register is then shifted right eight times with Os inserted on the left Each time a 1 is shifted out on the right the following binary number is exclusive OR d with the 16 bit register value 1010 0000 0000 0001 4 25 Chapter 4 RS 232 C Link Protocol 4 26 As each additional byte is transmitte
136. ge While waiting for a message anything besides the DLE SOH or DLE ENQ is ignored Note that in a single circuit system the slaves must be able to safely ignore everything sent by other slaves Chapter 4 RS 232 C Link Protocol If a DLE SOH is received the BCC and the message buffer are reset The next code received must be a data code and must equal the station address or 255 if the station can receive broadcast messages If there is no match the station ignores the rest of the message and continues waiting for the start of the message If the station address matches it is added to the BCC The next code is received and must match DLE STX If it doesn t the station ignores the rest of the message Otherwise it starts building a message While building a message all data codes are stored in the message buffer and added to the BCC If the buffer overflows the receiver continues summing the BCC but the data is discarded If an error is detected it is recorded If any control code other than a DLE ETX BCC is received the error flag the BCC the message size and the address optionally are all checked If any of the tests fail the message is ignored If the message is OK its header is compared to the last message If it is the same the message is discarded and a DLE ACK is transmitted If it is different the new header is saved and the message is sent to the message sink If the message can be stored a DLE ACK is sent If
137. ght and entering the error state 2 Reply errors numbered between 50 and 59 and detected by the local station when a reply is received 3 Remote errors numbered from 80 to 89 and returned in the reply message from the remote station as the result of errors in execution of a message at the remote station It should be noted that a Data Highway module will continue to generate replies as long as it is functioning properly These errors are contained in the STS byte of the reply message 4 Local errors numbered 90 to 99 and detected by the local station they are the result of being unable to properly transmit on the highway Error numbers are listed and explained below 01 No longer used In revisions previous to for 1771 KA this code could be set as a result of intermittent hard errors on the KA to PC cable 02 The pre scan aborted because the test codes in RACKO are bad This error should never occur because if the test codes are ever bad the PC should fault before the KA ever gets to the pre scan 03 The KA or KG does not have enough internal memory to store the start bit index This should only occur if the communication rung is very large To correct this the communication zone can be shortened perhaps by combining commands or windows It may also occur if a RAM hardware error corrupts the internal memory organization 04 The first element of a memory access branch is not a GET This condition can only be dete
138. he UART is like a small bridge and the mutual exclusion mechanism is like two flagmen one at each end of the bridge If two heavy trucks one called XMIT and one called RCVE come to the bridge at the same time the flagman on that side lets one through and makes the other wait When the first truck has crossed the bridge the flagman on the far side signals the first flagman who then allows the second truck to cross In a similar manner TXALLOC and TXFREE work together to ensure that XMIT and RCVE do not try to use the UART at the same time 11172 1 10 Appendix B Detailed Flow Charts Figure B 11 SENDCTL Subroutine Input TXALLOC E Message address Allocate UART or Wait SEND Transmit DLE SEND Transmit Control Code TXFREE Deallocate UART RETURN Nc 111734 B 11 Appendix B Detailed Flow Charts Figure B 12 SENDTX Subroutine SENDTX Input BCC TXALLOC Allocate UART Common or Wait RESP The Response Code Variable SEND Transmit DLE SEND Transmit ETX SEND Transmit CRC Low Byte 2 Previous Response Code at RESP SEND Transmit CRC High Byte TXFREE Deallocate UART EN C RETURN D 1117441 B 12 Appendix B Detailed Flow Cha
139. he error code is in the high nibble Since the full duplex message packet is actually transmitted on the highway itself in a encapsulated form the contents of the STS byte is what other PC highway stations use to generate the error word in the PC application program To decode the contents of the STS byte refer in section titled ERROR WORD in User Programming to error codes 80 89 for remote errors and error codes 90 93 for local errors For remote station errors make sure the error codes correspond to the processor type at that station either PLC PLC 2 or PLC 3 Match the last digit of the error code with value in hex in the appropriate nibble For example if the STS byte contains 04H the low nibble 4 and the high nibble is 0 indicating a local error Referring to the local error codes 90 01 04H matches to error 94 contention on the highway 7 35 Chapter 7 Error Reporting 7 36 PLC 3 NOTE With PLC 2 compatibility mode for the 1775 K A PLC 2 level commands addressed to a PLC 3 will only return errors as described above that is in the STS byte format In addition to the above PLC 3 can also create a second layer of error codes relative to PLC 3 type commands CMD byte 15 If the command is a PLC 3 level command addressed to a remote PLC 3 then the remote error returned from the 1775 KA will have an additional status byte stuffed into the data area called an EXT STS If there is a non zero error value
140. he flow charts and in many cases such error checking and recovery are not needed B 1 Appendix B Detailed Flow Charts Figure B 1 Data Flow Diagram for Full Duplex Protocol Data Link Layer Messages Which Have Been Sent Or Have Failed ome Bytes Messages SENDETX XMIT DLE ENQ Messages to be sent Physical Link Network Layer Layer DLE ACK DLE ACK UART i 4 Separator DLE NAK Empty Buffers Row Input g Bytes GETCODE 9 RCVE DLE ENQ Received Messages 11163 1 2 Internal Storage w Counter w Timeout Counter Legend w Default value used by the module Appendix B Detailed Flow Charts Figure B 2 Transmitter Routine for Full Duplex Protocol C XMIT E p GETMSG Get Message from Network Layer Reset and Timeout Counters SENDM Send Message WTAK SENDCTL Wait for ACK Send NAK or Timeout i DLE ENQ s 3 Timeouts for this Message 3 Received NAKs DLE NAK Received for this Message Received DLE ACK Yes Y SIGFAIL SIGOK SIGFAIL Tell Network Tell Network Tell Network Layer of Layer Message Layer of Failure Was Sent Failure 11164
141. he modules RTS is a request from the module to the modem to prepare to transmit With full duplex protocol RTS is always asserted With half duplex protocol it is turned on when the module has permission to transmit otherwise it is off CTS is a signal from the modem to the module that indicates the carrier is stable and the modem is ready to transmit The module will not transmit until CTS is on If CTS is turned off during transmission the module will stop transmitting until CTS is restored DTR is a signal from the module to the modem to connect to the phone line i e pick up the phone The module will assert DTR all the time except during the phone hangup sequence Modems built to American standards will not respond to DTR until the phone rings Some European modems will always pick up the phone whether it is ringing or not The KE KF module will not work with these types of European modems DSR is a signal from the modem to the module that indicates the phone is off hook It is the modem s answer to DTR The module will not transmit or receive unless DSR is on If the modem does not properly control DSR or if no modem is used DSR must be jumpered to a high signal at the module s RS 232 connector It can be jumpered to DTR DCD is a signal from the modem to the module to indicate that the carrier from another modem is being sensed on the phone line It will not be asserted unless the phone is off hook Data will
142. his error are Connection of two operating highways Connection of a powered up module to an operating highway Noise on the highway 7 8 Error Codes for 1775 KA Chapter 7 Error Reporting Bad cabling or connections Error 93 is rare but not impossible on a well functioning highway If it persists the internal diagnostic counters should be used to pinpoint the location of the faulty module or cable This error code corresponds with STS code 03 Local and Remote Error Bits As a diagnostic tool these bits are useful to identify the rung that caused an 80 or 90 series error The remote error bit indicates that a message was received from the remote station that some condition there prevented successful execution of the message When a remote error is indicated there is probably nothing wrong with the local station or with the highway cable The remote station is most likely working properly The first causes to investigate are indicated by the various codes Setting of a local error bit indicates that the local module is not able to confirm delivery of the command message to the remote station or that the command rung timed out before the reply message arrived A local error does not necessarily mean that the message was not received at its destination or that it will not be executed This section describes error codes that the 1775 KA module will report to the PLC 3 application program Errors are of three types
143. ides the flexibility of easy re configuration or expansion if you want to be able to add more stations later and it also provides more error checking than an RS 232 C link Software Layers Each of the physical links just described requires three layers of software to enable communication to take place The layers are defined as follows Application layer controls and executes the actual tasks or commands specified in the communication between stations To program this layer use the commands described in chapter 5 Network management layer handles queuing sequencing routing and error status reporting for communication If your physical link contains only Allen Bradley PCs you do not have to program this layer Otherwise refer to chapter 5 for a description of how to program this layer for an RS 232 C link to a computer Data link layer controls the flow of communication over the physical link by establishing maintaining and releasing the communication channel between stations If your physical link contains only Allen Bradley PCs you do not have to program this layer Otherwise refer to chapter 4 for a description of how to program this layer for an RS 232 C link to a computer 2 8 Chapter 2 Communication Concepts Application Layer The application layer concerns the specific commands that you can program at a given station to cause that station to communicate over the link This layer is the same for both RS
144. ins the number of the PC program rung that generated the command and SQN contains the transmission sequence number For command messages transmitted by your computer station your application programs can use the RNG and SQN bytes together to store a single 16 bit transaction number For command messages transmitted by a PC station the station interface module assigns the TNS values For each command message transmitted by your computer station your network level software must assign a unique 16 bit transaction number and a simple way to generate this number is to maintain a 16 bit counter at the network layer Increment the counter every time your command initiator application program creates a new message and store the counter value in the two TNS bytes of the new message 5 5 Chapter 5 Message Packet Formats 5 6 When the command initiator receives a reply to one of its command messages it can use the RNG and SQN bytes to tie the reply message to its corresponding command If the RNG and SQN bytes of a reply message match the RNG and SQN bytes of a command message then that reply is the appropriate one for that command Whenever your command executor receives a command from another station it should copy the RNG and SQN fields of the command message into the same fields of the corresponding reply message Do not change the RNG and SQN values in a reply message If you do the command initiator will not be able to match its
145. ith NAK SOURCE XMTR LINK RCVR SINK Data DLE STX Noise DLE ETX BCC gt DLE DLE STX Data DLE ETX BCC lt lt Not Full Data ACK Note that the message sent for the second poll is the same as the first since the first transmission was not ACKed Trias Figure 4 11 Message Transfer with Timeout amp ENQ SOURCE XMTR LINK RCVR SINK DLE STX DLE ETX gt Data NotFull Dat gt pL Nose CK Timeout DLE ENQ SS DLE ACK 11136 1 4 16 Chapter 4 RS 232 C Link Protocol Figure 4 12 Message Transfer with Retransmission SOURCE XMTR LINK RCVR SINK Data DLE STX Data DLE ETX BCC gt NotFull Dat DL Nose CK Data Timeout DLE ENQ R DLE DLE STX Data DLE ETX BCC gt Message Discarded pLE ACK Retransmission occurs when noise hits both sides of the line This type of noise destroys the DLE ACK while also producing invalid characters at the receiver The result is that the receiver changes its last response to NAK and the transmitter retransmits the original message Note that this is detected as a duplic
146. k Layer Communication Concepts This chapter presents some of the concepts of communication with the KE KF module It describes the physical communication links to the module and the various levels of software necessary to make those links work A KE KF module connects a computer or programmable controller to an Allen Bradley Data Highway In doing so the module acts as an interface between two physical communication links Data Highway link RS 232 C link The Data Highway link provides peer to peer communication between the module and other stations on the Data Highway It uses a half duplex polled protocol and rotation of link mastership In addition to a physical link layer communication on either the Data Highway or the RS 232 C link involves three levels of software programming Application layer 1 Network management layer Data link layer If you are using a computer on a RS 232 C link you must program all three layers For the Data Highway you need program only the application layer the Data Highway interface modules automatically take care of the other two layers The rest of this chapter presents some of the concepts behind the physical communication links and their three software layers For more details on the application and network layers refer to chapters 5 and 6 For more information on the data link layer of the RS 232 link refer to chapter 4 The physical link layer is a set of cables and interfac
147. l Duplex Modules Chapter 7 Error Reporting 20 Maximum number of NAKs accepted per message preset to 10 21 Maximum number of ENQs sent per message preset to 10 22 Current NAK count 23 Current ENQ count PLC 2 PLC The full duplex protocol and its half duplex variation provides for a message packet that contains a reply to have a status byte reserved in its header This byte known as the STS byte provides information about the execution or failure of the corresponding command that was transmitted from the computer A reply that returns zeros in the STS byte means the command was executed at the remote station Non zero status can be divided into two categories remote errors and local errors Remote errors mean that a command was successfully transmitted by the Data Highway controller to another Data Highway station but the remote station was unable to execute the command The remote station then formatted a reply with the STS byte containing some error code Local errors mean that the Data Highway controller was unable to transmit the message to the remote station The local station then turns the command around stuffs the STS byte with the appropriate error code and returns it to the sender computer The error code format is as follows When the error is local the high nibble 7 4 is zero and the reference to a particular code is in the low nibble as a Hex value When the error is remote the low nibble is zero and t
148. l not cause the setting of an error bit or done bit 53 A reply message has been received for which the start bit is off This could mean that the user program turned off the start bit before the done bit came on or that the automatic timeout is too short This error often follows a 36 or 37 error This error will not cause the setting of an error bit or done bit 54 Runtime command rung syntax check failed This is probably the result of on line editing This error will cause the module to enter the error state See error 30 55 Reply received while PROG light is on or during program mode This will possibly occur if messages are being executed remotely at the time a runtime syntax check fault occurs or if the keylock is turned to program mode while messages are being executed This will not cause the setting of an error bit or done bit 56 The sequence number in a reply message does not match the one being waited for This is to be expected if the start bit is turned on a message is sent then the start bit is turned off and on again before the done bit is set This error will not cause the setting of an error bit or done bit Chapter 7 Error Reporting 57 A reply message has an incorrect size This should not occur except during the debug of a new highway computer program This will not cause the setting of a done bit or error bit 81 This error is sent from the remote station if the command message was incorrect Thi
149. ld and a 1 byte SIZE field are missing after the FNC byte in the command message 2 The number of bytes of data requested in the SIZE field is greater than the maximum number allowed per reply packet 244 or SIZE is 0 zero 50 85 The command is an illegal request to read from the 1775 KA module s backplane window Diagnostic Status Command EXT STS Code STS Code Error if applicable if applicable Code Possible Causes 40 A backplane error occurred during determination of the physical ad dress of the end of the ladder program or of the end of user memory PLC PLC 2 Word Write Commands EXT STS Code STS Code Error if applicable if applicable Code Possible Causes 10 1 A 2 byte ADDR field is expected after the TNSW word but only one byte is present 2 There is an odd number of data bytes in the command packet 3 The ADDR value is odd that is it does not specify a word address 30 83 The local 1775 KA module has executed a shutdown request to the local PLC 3 processor timeout disconnect 50 85 1 The destination file does not exist in PLC 3 memory 2 The destination word does not exist in the destination PLC 3 40 84 Local PLC 3 backplane error either memory parity or file 60 86 Local keyswitch setting prohibits writing into desired destination file 70 87 The local PLC 3 processor is in program mode There may or may not be a major system fault 7 15 Chapter 7 Error Reporting
150. least 2 bytes of data after the end of the block address 2 There is an odd number of data bytes after the end of the block address 3 Sum of packet offset and size values specifies more than 65 535 words 4 Sum of packet offset and size is greater than total trans action size 30 83 The local 1775 KA module has executed a shutdown request 40 84 Backplane error either memory parity or timeout disconnect 60 86 Keyswitch setting disallows access 70 87 Local PLC 3 is in program mode 1 FO 231 There is an error in converting the block address major section gt 63 context gt 15 or section gt 15 2 FO 232 Three or fewer addressing levels specified in for a PLC 3 word address 3 FO 233 Conversion of a file address to block address resulted in more than 9 addressing levels 4 FO 234 Symbolic address not found 5 FO 235 Symbolic address is of length zero or is longer than 8 bytes 6 FO 236 1 Destination file not found 2 Destination address does not point to a word for word range writes or a file for file writes 3 Destination address specifies more levels than required 4 First word of destination location does not exist 7 FO 237 1 Any word in the total transaction does not exist in the destination file 2 Fora file write the source and destination files are not the same size 8 FO 238 Destination file size changed between packets of a multi packet transaction and became too small for the total transaction
151. lect State In order to leave this state you will have to manually select a mode at the Industrial Terminal Enter Upload Mode If you are using a 1771 KA series A revision F module or a 1771 KG series A use the Enter Download Mode command 07 function 04 shown above in section Enter Download Mode before sending physical read commands If you are using a 1771 KA2 module or a 1771 KG series B use the Enter Upload command 07 function 06 shown below before sending physical read commands Chapter 5 Message Packet Formats Enter Upload Mode This command puts the PLC 2 processor into the upload mode Use this command on a PLC 2 station before attempting to send any physical read commands to the station Command Format Te 07 06 Reply Format Borie When you send an Enter download upload mode command the industrial terminal port is disabled until you send an Exit Download Upload mode command When the industrial terminal port is disabled it enters the Mode Select State In order to leave this state you will have to manually select a mode at the industrial terminal Exit Download Upload Mode This command takes the PLC 2 processor out of the upload or download mode Use this command to restart the PLC 2 processor after performing an upload or download operation If you don t send this command after a download upload mode command you will have to recycle power at the 1771 KA or 1771 KA2 module to en
152. llation The bottom connector labeled COMPUTER RS 232 C connects to an intelligent RS 232 C compatible device The rest of this section explains how to make connections to this RS 232 C socket Figure 3 8 KE KF Module Connectors c m p m Data Highway socket I UC 15 pin connector Data M Highwa ue UT j Dropline DEOS pn cd cable socket not used 0 O t aS 30 C Adapter cable socket a Cat no 1770 CG or 1770 CP 25 Pin RS 232 C Ss Compatible Connector n pu up X 11120 1 3 18 Chapter 3 Installation Mechanical Characteristics The COMPUTER RS 232 C connector on a KE KF module is a female 15 pin D shell Note that this connector does not conform strictly to the RS 232 C standard which specifies a 25 pin male connector However you can use an RS232 C adapter cable cat no 1770 CG or 1770 CP to go from this connector to a standard 25 pin connector Electrical Characteristics Input and output levels on the RS 232 connector conform to the RS 232 C standard The transmitter has increased capability to drive an isolated line that is up to 7 000 feet long The length of this line determines the maximum communication rate on the RS 232 C link as indicated below Maximum Communication Rate in Line Length in Feet Bits Per Second Up up 2 000 19 200 2 000 to 4 000 9 600 4 000 to 6 000 4 800 6 000 to 7 000 2 400 The receiver ca
153. llowed For example Error 89 is primarily an indication of heavy use at one node rather than a faulted condition The appearance of a code like Error 89 is then a user application question and should be dealt with by understanding the trade offs between performance and node utilization Obviously pre scan errors 1 29 indicate a program problem and should be fixed immediately but merely trapping and halting on run time errors without understanding the relationship 7 1 Chapter 7 Error Reporting 7 2 of the error to loading factors and node utilization does not allow efficient operation of the Data Highway A troubleshooter should also make full use of the counter high byte in the error word to record frequency of errors This contributes to any application solution that requires redistribution of node traffic The error code word is four BCD digits wide The uppermost digit is not displayed by the Industrial Terminal in the GET instruction in the header rung but this is the least valuable part of the error code and can often be ignored If necessary this number can be easily displayed using GET BYTE and a PUT The lower two digits are always the error number Each number indicates a different condition which is explained in the paragraphs below The meaning of the upper two digits varies depending on the error number There are about 50 different error numbers that can be broken up into two major and four minor groups Pr
154. mes a message can be retransmitted If this limit is exceeded the message source will be signalled of the failure and the transmitter will proceed with the next message If the timeout expires before a response is received the transmitter sends a DLE ENQ on path 1 to request a retransmission of the last response on path 2 It restarts the timeout and waits for a response This too can be repeated several times and there is a user defined limit on the number of timeouts that are allowed per message If the enquiry limit is exceeded the message source will be signalled that the transmission has failed and the transmitter proceeds to the next message Chapter 4 RS 232 C Link Protocol Figure 4 7 Software Logic for Implementing Transmitter T Retransmit Same Message Message Packet DLE STX Data DLE ETX BCC Timeout Loop Received Received DLE ACK DLE NAK 2 3 3 NAKs Timeouts Received for this for this Message Message Legend No P j Recovery Procedure Ng DLE ENQ Ready to Transmit Next Message Default Values Used by the Module Y gt 11122 1 Since there are only two response codes defined there are no invalid response codes If the separator returns an invalid response code the transmitter will ignore it A more precise and detailed description of the actions of the transmitter appears below in structured
155. module s RS 232C port to set switch 4 use handshaking signals on ignore handshaking signals of What to do next Now go to section titled Station Number to learn about station numbers Station Number Switch groups SW 2 SW 3 and SW 4 are for setting the station number of the KE KF module The station number is an encoded 3 digit octal number that identifies the KE KF module as a unique station on the Data Highway Valid station numbers for the KE KF module are 010 to 077 and 110 to 376 octal Figure 3 4 shows an example of how to set the KE KF station number to 037 octal The switches in group SW 2 set the first left most digit of the station number switch group SW 3 sets the middle digit and switch group SW 4 sets the last right most digit Station numbers play an important part in the polling scheme described in chapter 2 They can also influence the order in which mastership is transferred between Data Highway stations Therefore we recommend that you always begin numbering stations with the lowest possible number and continue with the next available number in sequence Chapter 3 Installation Data Highway Communication Rate Switch assembly SW 5 lets you select the communication rate for the KE KF module s Data Highway port NOTE Set both switches ON for a communication rate on the Data Highway of 57 600 bits per second Be sure to set all Data Highway modules for this communication rate
156. mpting any of the installation steps The KE KF module has 6 switch assemblies Figure 3 1 that enable you to select various communication options The switch assemblies and their corresponding options are Switch Assembly Communication Option SW 1 RS 232 C link features SW 2 SW 3 SW 4 Station number SW 5 Data Highway communication rate SW 6 RS 232 C link communication rate and parity If you have a revision A G module Read section titled RS 232 C Link Features Revisions A G to learn how to set your switches in switch assembly SW 1 If you have a revision H module Read section titled RS 232 C Link Features Revision to learn how to set your switches in switch assembly SW 1 3 1 Chapter 3 Installation Figure 3 1 Communication Option Switches Station number hort SW 2 SW 3 SW 4 Data Highway communication rate SW 5 RS 232 C link communication RS 232 C link features Mn SW 1 x rate and parity SW 6 01 2 012 3 01 2 3 01 2 Q1 2 3 4 5 9 N N M Q1 2 3 4 0 0 0 0 1 POULE S X ON ON ON OFF OFF OFF Front view Side view 11112 1 Figure 3 2 RS 232 C Link Features Switch assembly SW 1 A A A Diagnostic commands
157. n Receiver Actions Since the receiver gets dirty input from the physical world it is more complex and must be capable of responding to many adverse situations Some of the things that can conceivably happen are listed here 1 The message sink can be full leaving the receiver with nowhere to put a message 2 message can contain a parity error 3 BCC can be invalid 4 The DLE STX or DLE ETX BCC may be missing 5 The message can be too long or too short 6 spurious control or data code can occur outside a message 7 A spurious control code can occur inside a message 8 The DLE ACK response can be lost causing the transmitter to send a duplicate copy of a message that has already passed to the message sink A record of the last response sent on path 2 is kept The value of this response is either ACK or It is initialized to NAK When a DLE ENQ is received the receiver sends the value of the last response from this variable A record is kept of several message header bytes If a message has the same header as the previous message the message is ACKed but discarded The receiver ignores all input from path 1 until a DLE STX or a DLE ENQ is received If anything other than a DLE STX or DLE ENQ is received on path one the receiver sets the last response variable to a NAK If an ENQ is received the last response is sent on path 2 and the receiver continues waiting for input If a DLE STX is re
158. n sense the signal generated by a similar transmitter and it is electrically isolated from all other circuitry on the module It consists of an opto isolater circuit with an input and return line at the RS 232 C connector AII other signals on the RS 232 C connector are driven and received by standard RS 232 C interface circuits which have maximum drive capability of 50 feet Cabling Cabling for the RS 232 C port of the KE KF module will vary depending on your application In general the pinouts for this cabling are as follows Standard RS 232 KE KF Module 15 pin Signal Abbreviation 25 pin Connector Connector Chassis shield drain 1 1 0 8 mmus oe signal ground data carrier detect When communication option switch 4 of switch group SW 1 is on section titled RS 232 C Link Features Revision A G the RS 232 C port of the KE KF module can transmit or receive all of the above signals If 3 19 Chapter 3 Installation 3 20 communication option switch 4 of switch group SW 1 is off section titled RS 232 C Link Features Revision A G then the RS 232 C port uses only TXD RXD and GND and TXDRET and RXDRET for longlines The definitions of the above signals are TXD carries serialized data It is an output from the module is serialized data input to the module and RXDRET are isolated from the rest of the circuitry on t
159. nabled 5 15 Chapter 5 Message Packet Formats 7 8 1 Protected commands disabled Bit 12 0 Embedded responses enabled 1 Embedded responses disabled Bit 13 0 Unprotected commands enabled 1 Unprotected commands disabled Bit 14 0 Privileged commands enabled 1 Privileged commands disabled Bit 15 0 Half duplex protocol 1 Full duplex protocol Starting byte address of diagnostic timers and counters Module series and revision level Bits 0 to 4 0 Revision A 1 Revision B etc Bits 5 to 7 0 Series A 1 Series B etc Not used eight 13 byte groups of processor status data one group for each of eight possible controllers on the loop If a particular controller on the loop is not active or does not respond to the diagnostic status command its 13 status bytes will all be zeroes Otherwise each group of processor status bytes will contain the following information Byte 1 Program I D 2 Processor 3 Pointer to start of program 4 Pointer to end of available memory 5 Size of I O 6 Processor error code 7 Error word address low byte 8 Error word address high byte 9 Processor mode 10 Pointer to END statement low byte 11 Pointer to END statement high byte 12 Pointer to end of used memory low byte 13 Pointer to end of used memory high byte 5 16 Chapter 5 Message Packet Formats Table 5 C Contents of Status DATA for 1775 KA Modules Byte Meaning
160. nd command executors This corresponds with the two message types Command messages sent by command initiators to command executors Reply messages sent by command executors in response to command messages received from command initiators Each command message requires one reply message Command initiators specify which command function to execute at a particular destination station The command executor at that destination station is responsible for interpreting the command message and executing the specified command function The command executor also issues a reply message for each command it receives If it cannot execute the received command the command executor must generate the appropriate error message Internally the KE KF module uses a routing subroutine and an message queue to implement the network layer When the module receives a message over its RS 232 C port it puts that message in the queue The routing subroutine then takes the message from the queue and transmits it over the Data Highway link The module also queues messages received from the Data Highway and the routing subroutine retransmits those messages over the RS 232 C link Figure 5 1 illustrates this model Chapter 5 Message Packet Formats Figure 5 1 Application Model Command Command Initiator Executor Q Q Commands Replies Replies Commands Y Y R R Network
161. nd motion control devices operator interfaces sensors and a variety of software Rockwell is one of the worlds leading technology companies Worldwide representation Argentina e Australia e Austria e Bahrain e Belgium Brazil e Bulgaria e Canada Chile e China Colombia e Costa Rica Croatia e Cyprus e Czech Republic e Denmark Ecuador e Egypt El Salvador Finland e France Germany Greece e Guatemala e Honduras e Hong Kong Hungary e Iceland e India Indonesia e Ireland e Israel Italy e Jamaica Japan e Jordan Korea Kuwait e Lebanon e Malaysia e Mexico e Netherlands e New Zealand e Norway Pakistan e Peru e Philippines e Poland e Portugal e Puerto Rico e Qatar e Romania Russia CIS e Saudi Arabia e Singapore Slovakia Slovenia e South Africa Republic e Spain e Sweden Switzerland Taiwan e Thailand Turkey e United Arab Emirates e United Kingdom e United States Uruguay Venezuela e Yugoslavia Allen Bradley Headquarters 1201 South Second Street Milwaukee WI 53204 USA Tel 1 414 382 2000 Fax 1 414 382 4444 Publication 1771 6 5 15 February 1985 PN 955096 87 Supersedes Publication 1771 822 March 1984 Copyright 1986 Allen Bradley Company Inc Printed in USA
162. nected Communication Interface Module cat no 1773 K A A variety of minicomputers and microcomputers In point to point configuration the KE KF module connects one intelligent RS 232 C device as a single station on a Data Highway Figure 1 2 illustrates this configuration Point to point links can use either peer to peer full duplex or master slave half duplex communication In a multidrop configuration one intelligent RS 232 C device connects to several Data Highways through sets of modems and KE KF modules Figure 1 3 illustrates this type of configuration If the multidrop link consists of broadband modems you can select either peer to peer full duplex or master slave half duplex communication If the multidrop link consists of baseband modems you must use master slave half duplex communication because baseband modems support only one communication channel Figure 1 2 Point to Point Links Computer Modem F Moden link Modem Computer RS 232 C link 50 cable ft max KE KF KE KF module module lt Data Highway Link KE KF module Allen Bradley longline RS 232 C link 7 000 cable ft max 1771 KG module PLC 2 30 processor 11104 1 Chapter 1 Introduction In either type of configuration there are three possible ways you can connect the KE KF module Direct connection
163. ng Diagram 11123 1 Figure 3 12 Connection to 1773 KA or 1775 KA Module User Supplied Male Connectors Chapter 3 Installation User Supplied Cable RS 232 C Belden 8723 or Equivalent RS 232 C 0 AM KE KF Cat No 1778 CR 0 1775 Module 15 Pin Male 25 Pin Female Connector Connector a Connection Diagram 15 Pin Male 25 Pin Female Connector Connect the Shield Connector at One End Only RS 232 C PORT Connector of 1771 KE KF Module 1 2 14 13 11 v User Supplied Cable Belden 8723 or Equivalent 7000 Ft Max _ User Supplied Male Connectors Wiring Diagram RS 232 C 1 PORT Connector of 1773 KA 3 or 1775 KA Module 25 2 7 4 5 6 8 20 11124 1 3 25 Chapter 3 Installation Diagnostic Indicators 3 26 After detecting DCD the module continues to monitor the DCD line If DCD goes off the module restarts the timeout If DCD is not restored within the timeout the module initiates the hangup sequence This feature allows the remote station to re dial in the event that the connection is lost through a fault in the phone network As soon as DCD goes off the module responds to any commands that it has received from another data highway station and that it still has sto
164. not be received at the RS 232 connector unless DCD is on With full duplex protocol the module will not transmit unless DCD is on If the modem does not properly control DCD or if a modem is not being used DCD must be jumpered to DTR at the module TXDRET is the return signal for TXD It is connected to module logic ground through a resistor It does not conform to RS 232 C specifications RXDRET is the return signal for It is connected to the isolated receiver and is isolated from all other circuitry on the module It does not conform to RS 232 C specifications If you are connecting a KE KF module to a device e g modem or computer not manufactured by Allen Bradley then you must mount the module within 50 cable feet of that device For such applications the module s GND must be connected to the GND of the modem or computer RXDRET must be jumpered to GND at the module TXDRET should be left open Note that this type of connection does not provide electrical isolation between the module and the connected device Direct Connection to a Computer Chapter 3 Installation To connect the module directly to a computer you can use a data terminal interface cable cat no 1770 CG This cable plugs into the COMPUTER RS 232 C connector on the module and the RS 232 C compatible connector on the computer Figure 3 8 The 1770 CG cable is 16 5 feet long If you need a long cable or a male female ada
165. ntains the ASCII code for the second character and so on If the symbol name is more than 8 characters long encode only the first 8 characters To use a symbolic address in a command message encode the symbol in the field labeled ASCII symbol in the command message formats chapter 5 Note that the message format show a byte of value zero before and after the symbolic address field You must include these zero bytes because they act as delimiters to distinguish the symbolic address from other fields in the message NOTE PLC 3 controllers can also transmit commands that contain symbolic addresses If you plan to transmit this type of command message to your computer from a PLC 3 station then you must write computer application programs that are capable of accepting these commands and interpreting the symbolic addresses General ERROR WORD in User Programming 1771 KG 1771 KA and 1774 KA Modules Error Reporting This chapter contains a list of error codes associated with Data Highway start up and run time situations The error information is available in three places the PC application program the internal error counters in each module and the STS byte in the header of a message packet The first section deals with the PC application program s error word and is the most accessible to the user The second section lists internal error counters bytes of information stored in RAM in each Data Highway module These numbers
166. o 7 0 57 600 bits per second 1 76 800 bits per second 2 38 400 bits per second 3 115 200 bits per second Chapter 5 Message Packet Formats Table 5 B Contents of Status DATA for 1773 KA Modules Byte Meaning 1 Operating status of controllers on the loop Bit 0 1 if controller 1 is active Bit 2 1 if controller 3 is active Bit 3 1 if controller 4 is active Bit 4 1 if controller 5 is active Bit 5 1 if controller 6 is active Bit 6 1 if controller 7 is active Bit 1 1 if controller 2 is active Bit 7 1 if controller 8 is active 1 Protected command disabled 2 Station interface type Bits 0 to 3 8 1773 KA data highway port 9 1773 KA RS 232 C port Bits 4 to 7 8 PLC 4 Microtrol processor 3 4 Data Highway port options Bit 0 0 57 600 bits per second 1 38 400 bits per second Bit 1 Not used Bit 2 0 Privileged commands enabled 1 Privileged commands disabled Bit 3 0 Unprotected commands enabled 1 Unprotected commands disabled Bit 4 0 Protected commands enabled Bit 8 to 15 Octal station number 5 6 RS 232 C port options Bit 0 0 Even parity 1 No parity Bit1 to 3 0 19 200 bits per second 1 9600 bits per second 2 4800 bits per second 3 2400 bits per second 4 1200 bits per second 5 600 bits per second 6 300 bits per second 7 110 bits per second Bit5to7 Not used Bits 4 to 10 Not used Bit 11 0 Protected commands e
167. ocessors If your computer has this type of word order your communication driver must handle the task of byte swapping as it loads data into a buffer Successive bytes received from the PC must be stored in the following order 1 0 3 2 5 4 7 6 9 8 Addressing There are three types of addressing a computer can use in command message that it transmits to PC stations Logical Physical Symbolic Logical Addressing Logical addressing refers to the type of addressing that a PC uses in its ladder diagram program to access its own data table memory This is the same type of addressing you would use in non privileged commands that is in commands that access only PC data table memory Because of the differences in PC memory organization the logical addressing scheme varies with controller type 6 6 Chapter 6 Data Manipulation Figure 6 6 Results of Transmitting low Byte First PC Word a Bit Number octal 17 16 15 14 13 12 11 10 07 06 05 04 03 02 01 00 11 11 1 Value A576 hex Odd high byte Even low byte b 16 Bit Computer Word with Right to Left Byte and Bit Order Bit number decima 15 14 13 12 1 10 9 8 7 6 5 4 3 21 0 ae aN 505 ae a 1 1 0
168. ogical addresses by means of pointers Since no two PLC 3 systems are configured identically the pointers are not fixed Therefore there is no algorithm for converting logical to physical PLC 3 addresses The PLC 3 physical address is a word address It goes in the 4 byte field labeled PLC 3 physical addr in the PLC 3 physical read or write command message format chapter 5 The format for this physical address field is PLC 3 Physical Address Frye Roa nea ABD Aer wo we AVG ATT See a5 n6 25 oe 8 76 urge aro Avs aval aval ara ner aro In this format A1 through A24 represent the 1 to 24 bits of the physical address value For example to address a command message to physical word address 12 200 decimal 002FA8 hex you would use the following binary code in the address field p o o tate cones a ao o oo Third byte Colo fol iL 1 gears The recommended procedure for uploading or downloading PLC 3 memory is to begin at physical address 0000 and proceed sequentially to the end of memory Since a single physical read or write command can transfer only about 120 words of data it will take many such commands to upload or download the entire PLC 3 memory Therefore each successive physical read or write should begin at the next physical address after the one where the previous command stopped Chapter 6 Data Mani
169. oint link or a multidrop broadband modem link you can use either peer to peer or master slave communication protocol For a multidrop baseband modem link you must use a master slave communication protocol because the link can support only one communication channel A computer can send or receive messages through a stand alone link in the same way as through a Data Highway network To do this the computer must be programmed to follow the communication protocol described in chapters 4 5 and 6 Configuration Considerations Allen Bradley manufactures a variety of communication interface modules for different applications At present these modules are PLC Computer Interface Module cat no 1772 CI PLC Communication Adapter Module cat no 1774 K A PLC 2 Family Communication Adapter Module cat no 1771 KA PLC 3 Communication Adapter Module cat 1775 K A 2 6 Chapter 2 Communication Concepts PLC 4 Communication Interface Module cat no 1773 K A PLC 2 Family RS 232 C Interface Module cat no 1771 KG Communication Controller Module cat 1771 KC KD KE KF The following sections summarize the uses of these modules PC Processor Data Highway Interface The following modules provide an interface between a PC processor and a Data Highway communication link PLC Communication Adapter Module cat no 1774 K A PLC 2 Family Communication Adapter Module cat no 1771 KA PLC 3 Comm
170. ollowing figures show some of the events that occur on various interfaces Time is represented as increasing from the top of the figure to the bottom Figure 4 17 Normal Message Transfer SOURCE SOURCE SINK MASTER LINK SLAVE SINK Data gt DLE SOH SIN DLE STX Data DLE ETX BCC gt NotFul Data DLE ACK OK 11142 1 Figure 4 18 Message Transfer with Invalid BCC SOURCE SINK SOURCE SINK MASTER LINK SLAVE Data gt DLE SOH STN DLE STX Noise DLE ETX BCC gt Timeout DLE SOH SIN DLE STX Data DLE ETX BCC gt lt NotFul _ Data Es DLE ACK OK 11143 1 4 31 Chapter 4 RS 232 C Link Protocol Figure 4 19 Message Transfer with ACK Destroyed SOURCE SINK SOURCE MASTER LINK SLAVE SINK Data gt DLE SOH STN DLE STX Data DLE ETX BCC gt NotFul Data gt Noise Timeout DLE SOH SIN DLE STX Data DLE ETX BCC gt DLE OK 11144 1 Figure 4 20 Poll with No Message Available SOURCE SOURCE SINK MASTER LINK SLAVE SINK NotFul gt DLE ENQ STN BCC NoMessage DLE EOT 11145 1 4 32 Chapter 4 RS 232 C Link Protocol Figure 4 21 Poll with Message Returned SOURCE SOURCE
171. ommand Format DST SRC CMD STS TNS FNC ADDR SET RESE 02 00 Up to 61 masks of this form Reply Format Protected Write This command writes words of data into limited areas of the PC data table memory Its access is limited by memory access rungs in the communication zone of the PC s ladder diagram program Chapter 5 Message Packet Formats Command Format DST CMD STS ADDR DATA Max of 243 bytes 00 X Reply Format Domo 00 Set ENQs This command sets the maximum number of ENQs that the station interface module will issue per message transmission Put the number in the DATA field The default setting for the KE KF module is 10 ENQs per transmission Command Format Exes evento 06 06 Reply Format relma Set NAKs This command sets the maximum number of NAKs that the station interface module will accept per message transmission Put the number in the DATA field The default setting for the KE KF module is 3 NAKs per transmission Command Format 06 05 Reply Format conni 5 19 Chapter 5 Message Packet Formats 5 20 Set Timeout This command sets the maximum amount of time that the station interface module will wait for an acknowledgement to its message transmission The setting is expressed as the number of cycles of an internal clock where 40 cycles equals 1 second Put the number of desired cycles in the DATA field The default setting
172. or a half second Each message will be re tried five times for memory overflow before it is returned to sender Poll timeout Counts the number of times that this station grabbed mastership of the highway because it timed out while waiting to hear a valid frame On a highway that has just been powered up there should be only one station that has this counter incremented False poll Counts the number of times that this station has tried to relinquish mastership and the station that was expected to take over failed to respond This happens often on a noisy highway because the noise is mistaken for a poll response and the wrong station is selected as the next master When this occurs the old master resumes polling It also can happen on a long highway if the poll response is very attenuated and is not picked up by the carrier detect circuit If the new station does respond but the old master does not hear it the old master will record a false poll and continue polling The new master will start polling also This usually leads to the second station detecting contention and relinquishing Receiver heard status Counts the number of times that the receiver received a status frame instead of a message frame This should occur only if a poll timeout is imminent a master has had mastership for more than 170 ms and the station has disabled its address recognizer to test for any valid traffic Frame too small Counts the number of frames that were rej
173. or more PCs and or a computer use a Data Highway network as shown in Figure 2 1 For 2 7 Chapter 2 Communication Concepts distances longer than the Data Highway itself provides you can use an auxiliary longline RS 232 C link or modem link With two stations you may want a stand alone link For a stand alone link a modem link can be used to provide communication between stations more than 10 000 cable feet apart Also with the full duplex peer to peer protocol and embedded responses it could be faster than a Data Highway link because it wouldn t be burdened with polling A Data Highway link has a communication rate of 57 600 bits per second and a half duplex peer to peer polled protocol An RS 232 C link has a selectable communication rate up to 19 200 bits per second and a selectable protocol of half duplex master slave polled or full duplex peer to peer unpolled For a stand alone link to a computer you may want to use the peer to peer communication protocol for maximum speed Or you may want to use the master slave communication protocol so that the computer can select the times it will communicate over the link A master slave communication protocol can be selected for any link to a computer A peer to peer communication protocol can be selected only for a point to point link or a broadband modem multidrop link to a computer Even with only two stations you may want a Data Highway link The Data Highway prov
174. pecifies the number of data bytes that the responding station must return in its reply message The allowed value for SIZE will vary with the type of command as indicated in the reply formats below Message Formats Chapter 5 Message Packet Formats DATA The DATA field contains binary data from the application program The number of data bytes in a message depends on the command or function being executed as indicated in section titled Message Packet Chapter 6 gives some details on the format for the data field This section presents the detailed message formats for each type of command and reply message For this presentation the command message formats are discussed in the following order use this command use this function If you want this command code code Basic command set Set NAKs 06 05 Set timeout 06 04 Chapter 5 Message Packet Formats Bit writes OF 02 Download request OF 05 Physical write Restart request Shutdown request Upload request Word range read Word range write PLC 4 commands Allocate Deallocate Initialize processor Physical read Physical write Physical write with mask Set to program mode Set to run mode OE 02 Set to single step test mode OE 04 5 8 Chapter 5 Message Packet Formats Basic Command Set Basic commands include those that can generally be executed by any PC station on the communication link regardless of the type of PC controller at
175. plication programming to maintain the proper byte and word order in PC data stored in the computer 6 5 Chapter 6 Data Manipulation Three factors that can influence the ability of your computer to handle PC data are The size of words in your computer s memory The left to right or right to left ordering of bits within a word in your computer s memory Whether the computer considers the low order byte of a word to have an even or an odd address If your computer uses something other than 2 byte 16 bit words you should design your application programs to make the proper conversions from PC word addresses to computer word addresses When stored in a computer each PC word should start on an even byte boundary Figure 6 6a shows a 16 bit word in PC memory Figure 6 6b shows a 16 bit computer word with right to left byte and bit order as in DEC PDP 11 34 or VAX 11 780 It also represents a 16 bit word in an 8 bit processor such as Zilog Z 80 or Intel 8086 microprocessor If your computer has this type of word order the conversion is straightforward Figure 6 6c shows a 16 bit computer word with left to right byte and bit order as in IBM Series 1 If your computer has this type of word order the conversion is more complex You will have to swap bytes into and out of buffers Figure 6 6d shows a 16 bit computer word with left to right byte order and right to left bit order as in Zilog Z8000 or Motorola 68000 micropr
176. pter cable you can construct your own according to the wiring diagram in Figure 3 9 Connect the cable shield at one end only Be sure that the cable length does not exceed the RS 232 C limit of 50 feet Figure 3 9 Connection to a Computer 15 pin Male n Corres 25 Pin Male Connector RS 232 C RS 232 C PORT connector Cable FE compatible PORT of KE KF connector of module computer a Connection Diagram RS 232 C RS 232 C PORT connector compatible PORT of KE KF connector of module computer 1 1770 CG Cable 16 5 Ft i nh 2 3 BB e 3 XX 2 BA 6 20 CD 8 e WY e 8 CF 11 6 e 4 4 CA 5 5 C8 25 Pin Male Connector Connector a Wiring Diagram 11120 1 3 21 Chapter 3 Installation Figure 3 10 Connection to a Modem 15 Pin Male 25 Pin Male Connector Connector RS 232 C RS 232 C PORT Connector 1770 CP Cable 16 5 Ft Compatible PORT of 1771 KG Connector of Module u 8 Connection Diagram RS 232 C RS 232 C PORT Companie Connector PORT of 1771 KG Connector of Module MODEM 1 J 1770 CP Cable 16 5 Ft 1 AA p 17 8 2 gt 2 BA e e 3 XX B 3 BB 4 _
177. pulation PLC 4 Microtrol PLC 4 Microtrol controllers use physical addresses that begin at 00 for the first word of memory and continue to 5FF hex for the last word of memory Figure 6 9 is a map of PLC 4 physical memory Figure 6 9 PLC 4 Physical Memory Physical Byte Address HEX Read only Force Table I O and Flags Store Bits Times Counters Program Area Sequencer Table 11162 1 Specifying a physical address in PLC 4 privileged commands requires 3 bytes The first byte is the identification number for a particular controller in the loop and it is labeled PLC 4 sel in the command message formats chapter 5 The next two bytes contain the physical address of a word in the selected controller s memory and they are labeled ADDR in the command message formats chapter 5 When encoding the physical address be sure to put the low byte of the address value in the first byte of the ADDR field Symbolic Addressing Symbolic addressing uses ASCII symbols to represent a logical address Only PLC 3 controllers can accept symbolic addresses Before using a symbolic address in a message you must first define the symbol at the PLC 3 that is to receive the message refer to publication 1775 801 6 15 Chapter 6 6 16 The symbolic address field can be from 1 to 8 bytes long The first byte contains the ASCII code for the first character in the symbol name the second byte co
178. r a file for file reads 3 The PLC 3 address specifies more levels than required 4 Word specified by the PLC 3 address does not exist 7 FO 237 1 Any of the destination words in the destination file do not exist 2 For a file read the source and destination files are not the same size 8 FO 238 The file size decreased between packets of a multi packet transaction and became too small for the total transaction 9 FO 239 File is larger than 65 535 words A FO 240 Sum of total transaction size and PLC 3 addressing is greater than 65 535 7 18 PLC 3 Bit Write Commands Chapter 7 Error Reporting Possible Causes EXT STS Code STS Code Error if applicable if applicable Code 10 81 30 83 40 84 60 86 70 87 1 FO 231 2 FO 232 3 FO 233 4 FO 234 5 FO 235 6 F0 236 9 F0 239 B F0 241 More than 4 bytes of data exist after the PLC 3 address in the com mand message The local 1775 KA module has executed a shutdown request Backplane error memory parity or timeout disconnect Keyswitch setting disallows access Local PLC 3 is in program mode Error in converting the block address major section gt 63 context gt 15 section gt 15 Three or fewer addressing levels specified in for a PLC 3 word address Conversion of a file address to block address resulted in more than 9 addressing levels Symbolic address not found Symbolic address is of length zero or is longer than 8 bytes 1 File not found
179. red in its receive buffer The module s response is to send the same command back to the source station along with an error code of 84 chapter 7 At the same time the module ignores any messages received over its RS 232 C link because it assumes that this link is terminated Note that this handshaking is necessary to guarantee access to the phone line If this handshaking protocol is defeated by improper selection of modem options or by jumpers at the connectors the modem may still answer a call But if the connection is lost the modem will not hang up It will then be impossible for the remote station to re establish the connection because it will get a busy signal Character Transmission The module sends data serially over the RS 232 C interface one 8 bit byte at a time The transmission format conforms to ANSI X3 16 CCITT V 4 and ISO 1177 with the exception that the parity bit is retained while the data length is extended to eight bits The transmission format may be summarized as follows start bit data bit 0 data bit 1 data bit 2 data bit 3 data bit 4 data bit 5 data bit 6 data bit 7 even parity bit optional one stop bit For communication rate and parity settings refer to section titled Data Highway Communication Rate There are 5 LED indicators on the front of a KE KF module Figure 3 13 These indicators can help you in diagnosing problems with the module s installation and operation The indicators are
180. remote error bit for the associated rung This error code corresponds with STS code 60 87 The remote PC is in PROGRAM or REMOTE PROGRAM mode or the remote KA is in download mode This error results in setting the remote error bit for the associated rung This error code corresponds with STS code 70 88 Execution of protected commands at the remote station is inhibited because its PROG light is on This error results in setting the remote error bit for the associated rung This error code corresponds with STS code 80 7 7 Chapter 7 Error Reporting 89 The remote station has no memory to store messages This error will only be signalled after 5 re tries at half second intervals it indicates that either a very heavy traffic load is being presented to the remote station or that the dynamic memory of the remote station is corrupted If the problem clears up after cycling power and does not recur the cause may be RAM or CPU failures triggered by heat or noise If the problem recurs repeatedly the probable cause is too many messages This error code corresponds with STS code 90 91 The RS 232 C port is not connected to a device or the DSR pin is not being asserted high true This error code corresponds with STS code 01 92 The local station cannot confirm delivery of acommand message to the remote station This does not necessarily mean that the message was not sent or that the done bit or remote error bit will not be
181. retransmissions from a station 11147 1 4 34 Chapter 4 RS 232 C Link Protocol Figure 4 23 Message Sink Full Case 1 SOURCE SINK SOURCE MASTER LINK SLAVE SINK Data DLE SOH SIN DLE STX Data DLE ETX BCC lt Full NotFull gt DLE ENQ STN BCG gt Message DLE EOT Sometime Later DLE SOH STN DLE STX Data DLE ETX BCC Not Full Data DLE ACK OK When a station times out it is a good idea to poll it to see if it is there If it answers with a DLE EOT toa message but consistently fails to ACK a message its message sink is probably full If it responds DLE EOT to a poll you must wait for the buffers to clear 11148 1 4 35 4 36 Chapter 4 RS 232 C Link Protocol Figure 4 24 Message Sink Full Case 2 SOURCE SINK MASTER LINK SOURCE SLAVE SINK DLE SOH STN DLE STX Data DLE ETX BCC gt Full Timeout NotFul gt DLE ENQ SIN Data DLE STX Data DLE ETX Data DLE ACK DLE SOH SIN DLE STX Data DLE ETX BCC gt Not Full Data lt lt OK When a station s message source and sink share a commom memory pool it may be that the message sink full indication results from an abundance
182. robably will succeed if it is re tried The remote station powered down or was disconnected from the highway while it was processing the message If the message is re tried it should get a 92 error 7 5 Chapter 7 Error Reporting 7 6 The timeout is too short The minimum recommended timeout value is 2 seconds With a resolution of one second this allows the actual timeout to occur as soon as one second or as late as 2 seconds A highway loading peak caused the timeout to be exceeded If this is a rare occurrence it might be acceptable to just re try the message Small lt 100 increases in the timeout should eliminate this problem Malfunction of a highway station is causing it to retain mastership for long periods of time Check for a station with a faulty receiver or a bad highway cable The internal diagnostic counters will be most helpful in tracking this one 50 Not used Prior to rev F 1771 KA this may have occurred if a PC hard error occurred while processing a reply message 51 The reply message contains an invalid rung number This should never occur unless PCs are sending messages to a computer program that is not yet functioning properly This error will not cause the setting of an error bit or done bit 52 A reply has been received at a PC that cannot send messages because it has no command rungs This should never occur unless faulty reply messages are sent by a computer under debug This error wil
183. rts Figure B 13 SEND Subroutine SEND Input Link Data Byte Common TXWAIT ASleep Variable Disable Processor Interrupts Enable UART Transmit Interrupt SLEEP UART No Transmitter Suspend at TXWAIT Yes Disable UART Transmit Interrupt Output Byte to UART Indivisible Zone Enable Processor Interrupts NOTE This figure assumes the use of 280 SIO Return 11175 1 B 13 Appendix B Detailed Flow Charts Figure B 14 SENDDATA Subroutine Input e Link Data Byte TXALLOC Allocate UART or Wait SEND Transmit Link Data Byte SEND Is Data ae DLE Transmit a j Second DLE TXFREE De allocate UART B 14 11176 1 Figure B 15 TXALLOC Subroutine _ TXALLOC Appendix B Detailed Flow Charts Yes SLEEP ag Wait at TXALWT Until UART is Free Set IN USE Flag Indivisible Zone RETURN Figure B 16 TXFREE Subroutine C TXFREE Reset IN USE Flag WAKEUP Continue Any Process at TXALWT RETURN Common N USE Flag eTXALWT A Sleep Variable 11177 1 eIN USE Flag eT XALWT A Sleep Variable 11178 1 B 15 Appendix B Detailed Flow Charts Figure B 17 TRANSMIT INTERR
184. s includes the command code subcommand code and size of the command or the requested reply size This error results in the setting of the remote error bit for the associated rung This error code corresponds with STS code 10 82 Not used for 1771 KA The meaning of this code has been assigned to verification errors within the host PC This error code corresponds with STS code 20 83 Some condition exists at the remote PC that requires manual intervention This error code corresponds with STS code 30 The cable between the module and the PC is unplugged The PC is faulted Either results in setting the remote error bit for the associated rung 84 Execution of a message at the remote station was aborted because of a hard communication error on the cable or on backplane access between the module and the PC This error results in the setting of the remote error bit for the associated rung This error code corresponds with STS code 40 85 An attempt to access an illegal address in the remote PC has aborted message execution Illegal accesses may result from Access outside the data table as defined at the remote station Access outside a memory access window protected commands only Either results in setting the remote error bit for the associated rung This error code corresponds with STS code 50 86 Execution of a command is disabled at the remote station by a DIP switch option This error results in setting the
185. s per second Bit 2 0 All other PLC 2 Family processors 1 PLC 2 processor Bit 3 0 Protected commands enabled 1 Protected commands disabled Bit 4 0 Unprotected commands enabled 1 Unprotected commands disabled Bit 5 Not used Bit 6 0 Physical writes enabled 1 Physical writes disabled Bit 7 0 Transmission of unprotected commands enabled 1 Transmission of unprotected commands disabled 1771 KG Module 5 13 Chapter 5 Message Packet Formats Bit 0 0 Half duplex protocol 1 Full duplex protocol Bit 1 0 Physical writes enabled 1 Physical writes disabled Bit 2 0 Unprotected commands enabled 1 Unprotected commands disabled Bit 3 0 Embedded responses enabled 1 Embedded responses disabled Bit 4 0 Even parity 1 No parity Bits 5 to 7 0 19 200 bits per second 1 9600 bits per second 2 4800 bits per second 3 2400 bits per second 4 1200 bits per second 5 600 bits per second 6 300 bits per second 7 110 bits per second 1774 KA Module Bit 0 0 Unprotected commands enabled 1 Unprotected commands disabled Bit 1 Not used Bit 2 0 Physical writes enabled 1 Physical writes disabled Bit 3 0 Transmission of unprotected commands 1 Transmission of unprotected commands enabled disabled Bit 4 0 Data highway port B is connected 1 Data highway port A is connected Bit 5 0 PLC outputs held in last state 1 PLC outputs turned off Bit 6 t
186. s station Number of poll messages received for this station Number of DLE EOTs sent Number of calls received Number of times that phone was hung up by the module Number of times that DCD was lost Number of times that the phone was hung up because of a DCD timeout INTERVAL EVENT COUNTERS 35 36 37 38 39 40 41 Number of messages routed to RS 232 port Number of commands routed to command executor Number of replies routed to reply processor Number of messages sent to self Number of routing errors on inbound messages Number of routing errors on outbound messages Number of messages with incorrect network address 7 31 Chapter 7 Error Reporting 7 32 42 43 44 45 46 47 48 49 50 51 16 bit count of messages sent by command initiator 16 bit count of commands received by command executor 16 bit count of replies sent by command executor 16 bit count of replies received by command initiator Number of breaks sent to IT Number of resyncs sent to PC Chapter 7 Error Reporting 1775 KA Diagnostic Counters DATA HIGHWAY PORT 1 Bad CRC on acknowledgement Local error A 2 acknowledgement before timeout occurred Local error B 3 Contention while master detected message transmission by another station 4 Acknowledgement contained an error Local error C D 5 Local errors Sum of A B and C abov
187. sage but did not send the reply in the allotted time cf error 92 02 92 The remote station specified does not acknowledge ACK the mes sage See discussion of Error 92 in section titled ERROR WORD in User Programming 04 94 Local port is disabled through LIST 112 1 Undefined assignment operator in assignment statement 2 Undefined operator in an expression 114 Illegal expression syntax 115 Illegal unary prefix operator in an expression 117 Undefined data following a valid address in a CREATE command or undefined data following a valid symbol in a DELETE command 121 Symbol undefined This will occur if a symbol appears as the source in an assignment command before it is defined as a symbol For example a statement of the form A A 6 will give this error if user symbol A has not appeared previously 123 System symbol must be a symbolic address This error will occur if a procedure name is used in place of a symbolic address in an assign ment statement or if the system symbol referenced in an assignment doesn t exist 124 Illegal destination in an assignment command This does not neces sarily mean that an assignment command was desired because any command line that doesn t look like anything else is assumed to be an assignment command Lines that will generate this error include 5 4 1 6ASDFGHJ Whereas the line WERTYUI will generate an error 140 unrecognized command 7 10 EXT STS Code if
188. st being able to allocate a receive buffer This will result in a memory overflow error when the next message is received Bad frame status Counts the number of frames that were rejected because of a bad CRC This error is very common on a noisy highway 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 Chapter 7 Error Reporting Buffer overflow Counts the number of times a message was received that contained more than 250 bytes Memory overflow Counts the number of times a message was received when there was no buffer space allocated for it This usually follows a memory full error Retransmits Counts the number of duplicate frames received A duplicate frame is sent by a transmitter when it fails to receive an ACK If the reason it failed to receive an ACK was that the ACK was lost rather than that the original message was lost the duplicate is redundant and should be discarded Any two successive messages between polls that have the same sequence number fields and the same command reply bit are assumed to be duplicates Aborts Counts the number of aborts received The HDLC abort signal is not used on the Data Highway but can be detected by the SIO in certain circumstances Some stations whose addresses match the ringing pattern after a transmitter shutoff can be particularly susceptible to this error stations 36 76 and 176 for example These numbers will d
189. station The rest of this section explains the network management layer for the Data Highway For the most part you need not be concerned with the interaction of station interface modules on the Data Highway This means that your application programs at the PCs and computers along the Data Highway need not involve themselves with inter station protocol handshaking or control of the Data Highway link This is all carried out automatically by the station interface modules However an understanding of station interaction is useful both to computer programmers and PC programmers It allows optimized use of Data Highway commands and fault diagnostics Error Checking Error codes can be generated at two places remote station modules and local station interface modules For codes that are returned from a local station module two types of conditions can exist Application programs use the wrong message format or issue illegal commands The local station cannot complete a transaction due to network problems A remote station can return only the codes associated with an application problem at the remote station Typically these involve either the PC processor being off line in Program mode for example or the command trying to access memory areas blocked by either the interface module or the user application program In the network layer protocol command message status is returned in a reply status byte A value of zero in the status by
190. ta Highway message type 210 Use of a non PLC 3 type address in a local address operand 211 In an assignment command one of the local files does not exist or the word specified is beyond the end of the file 213 A local file exists but the action specified refers to addresses beyond the end of the file Possible causes include 1 In a word assignment statement the offset is greater than the file size 2 In a word range assignment statement the sum of the base address and the offset is greater than the total file size 3 In a file assignment statement the destination file is smaller than the source file If the source file is remote a single packet will be fetched from the remote station s file 215 The value resulting from operations specified on the left side of an assignment statement will not fit into the destination specified on the right side 214 Local source and destination files differ in size 1 The source is in the H section and the destination is in the N section but the number is too large i e outside the range 32768 to 32767 2 A word is transferred from a binary section or B section to the N or C section and the high order bit is a 1 3 The destination is in the D section but the number is not a valid BCD bit pattern 217 More than 8 levels specified in file address 218 File size changed between packets of a multi packet transaction 230 Reply packet too small Reply Error Codes
191. tain a CMD byte To form the CMD value for a reply the network layer copies the CMD value from the corresponding command message and sets the reply bit bit 6 to 1 Figure 5 4 CMD byte Format Bit 7 6 5 4 3 2 1 0 0 r p 0 command 11153 1 The application layer supplies the FNC value and the command code bits 0 to 3 of the CMD byte for each command message The network layer supplies bits 4 through 7 of the CMD byte STS The STS status byte indicates the status of the message transmission In command messages the application program should always set the STS value to 0 In reply messages the STS byte may contain one of the status codes listed in chapter 7 Note that an STS value of 0 in a reply message means no error In a reply message the STS byte is divided between application layer and network layer The network layer uses bits 0 through 3 of the STS byte to report local errors those errors that occur when the network layer attempts to transmit a message across the link The application layer uses bits 4 through 7 of the STS byte to report remote errors those errors that occur when the command executor at the destination station tries to execute the command message Chapter 7 explains local and remote error codes TNS The TNS transaction bytes contain a unique 16 bit transaction identifier A complete transaction consists of a command message transmitted by a PC station RNG conta
192. tation For a PC the format is part of the PC user program For computer the formatting has to be done as part of the computer program chapter 5 A reply message is generated by a station in response to a command message it receives The reply message indicates that the command message was received and that the station interface module has completed the sequence of events required of it for command execution For commands that read data the reply message contains the data specified by the command For commands that write data the reply message indicates that the write operation has been completed at the receiving station When the replying station is a programmable controller the reply message is an automatic function of the interface module operation and is transparent to your program If the replying station is a computer you must program the computer to formulate the response and the reply message Chapter 2 Communication Concepts Figure 2 5 State Transition at Master Station Contention ee Sending lt State Have All Sent or Max of 16 or E is All High Priority Messages Have Been Polled Sent and Response to High at Least Priority Global Poll Once Y Received Polling Mastership State Relinquished Mastership Received x State 11110 1 Polling To transfer mastership between stations the station interface modules use an orderly polling scheme Normally
193. te called PLC 4 SEL This field specifies which controller in the PLC 4 Microtrol loop is the ultimate destination of the command message The allowed values for this field are PLC 4 SEL value Meaning 0 Selects controller 1 Selects controller 2 Selects controller 3 Selects controller 4 Selects controller 5 Selects controller 6 Selects controller 7 mn Selects controller 8 Allocate This command causes the 1773 KA module to allocate PLC 4 access privileges to the computer station that originated the allocate commands Once the computer has this access privilege it can send any of the other privileged commands to the selected PLC 4 controller No other computer can gain access privileges to the same PLC 4 controller until the privileges of the first computer have been de allocated If the 1773 KA module loses power all access privileges are de allocated 5 37 Chapter 5 Message Packet Formats 5 38 Command Format 0E 05 sel Reply Format A Format when successful execution G B Format when reporting n error melele E 4E STS Where the extended status byte is optional De allocate This command de allocates access privileges to the selected PLC 4 controller Command Format 0E 06 sel Reply Format A Format when successful execution Format when reporting an error CICIESEDESE 4E STS Where the extended status byte is optional Initialize Processor
194. te indicates successful transmission of the corresponding command It is up to the local application program to display and act on the value of the returned byte Data Link Layer The data link layer controls the flow of communication on the physical link by acquiring and releasing access to the communication channel for each station This layer differs for each type of physical link Chapter 4 explains how to program the data link layer for an RS 232 C link The rest of this section describes the data link layer of the Data Highway Chapter 2 Communication Concepts Note that you do not have to program the data link layer for the Data Highway the communication interface modules automatically take care of it The description of it presented here is solely for information purposes The protocol that is used between stations on the Data Highway link is a modified low level implementation of HDLC that features bit stuffing flag definition and generation of the cyclic redundancy check CRC Floating Master Central to the interaction of Data Highway modules is the concept of the floating master With this arrangement no single station is permanent master controlling the Data Highway communication link at all times Instead each station bids for mastership based on its need to send command or reply messages This arrangement has two major features Multiple masters Peer to peer communication One advantage of floating master
195. te the following commands which apply only to PLC controllers Disable outputs Enable program a Enable scan Physical read Physical write The above commands are privileged commands This means that only a computer can initiate them Their primary purpose is for uploading and downloading PLC memory Disable Outputs This command turns off all outputs of the PLC controller Use this command to disable the PLC s output before doing a physical write operation Command Format Te Tele E 07 00 Reply Format Borie Enable Program This command returns control of outputs to the PLC ladder diagram program Use this command to cancel the effect of the disable outputs command Command Format 07 01 Reply Format Chapter 5 Message Packet Formats Enable Scan This command restarts the PLC processor s program scanner after a physical write operation has been performed Note that you must always use the enable scan command to restart the PLC processor after a physical write command Command Format CPI 07 03 Reply Format el aol Physical Read This command reads bytes of data from the PC data table or program memory Use this command up to upload the contents of PLC memory to your computer Use the SIZE field to specify the number of bytes to be read To specify a number of PC words SIZE should be an even value because PC words are two bytes long Command Format
196. the addressed PC byte A 1 in a bit position of the RESET mask means to reset the corresponding bit in the addressed PC byte to 0 a 0 in a bit position of the RESET mask means to leave the corresponding bit in the PC byte unchanged Note that the interface module at the receiving PC station executes this command by first making a copy ofle at the receiving PC station executes this command by first making a copy of the addressed PC byte It then sets or resets the appropriate bits and writes the byte back into PC memory At the same time the PC processor can be changing the states of the original bits in memory Because of this some data bits may unintentionally be overwritten Command Format DST SRC CMD srS TNS ADDR SET RESE 05 Up to 61 masks ome form Reply Format Berges Unprotected Read This command reads words of data from any area of PC data table memory Use the SIZE field to specify the number of bytes to be read To specify a number of PC words SIZE should be an even value because PC words are two bytes long Command Format Reply Format E m 41 Unprotected Write This command writes words of data into any area of PC data table memory Command Format E ADDR DATA Max of 242 bytes N Reply Format conoi 5 21 Chapter 5 Message Packet Formats 5 22 PLC COMMANDS PLC stations can execute all of the commands in the basic command set They can also execu
197. the following binary calculation 0010 0000 20 hex 1101 1111 1s compliment gi 1110 0000 2s compliment hex 4 3 Chapter 4 RS 232 C Link Protocol Figure 4 1 Link Packet Format for Full Duplex Protocol From CMD STS FNC ADDR DATA Application Layer N b P Data From DST SRC CMD STS ib From Application Layer pra Data 11125 1 To transmit the data value 10 hex you must use the data code DLE DLE However only one of these DLE data bytes is included in the BCC sum For example to transmit the values 8 9 6 0 10 4 and 3 hex you would use the following message codes Represents single data byte value of 10 10 02 08 09 06 00 10 10 04 03 10 03 D2 In this case the sum of the data bytes is 2E hex because only one DLE text code is included in the BCC So the BCC is D2 hex The BCC algorithm provides a medium level of data security It cannot detect transposition of bytes during transmission of a packet It also cannot detect the insertion of deletion of data values of zero within a packet Two Way Simultaneous Operation On a two way simultaneous link there are only two physical circuits connecting 4 distinct and independent programs Referring to the diagram below transmitter and receiver B manage the transfer of messages from station A to station B by sending message packets from A to B and returning respons
198. thing other than a or a number followed a in an extended address Unrecognized section specifier An illegal character followed the in an address Bad timer or counter specification 1 The first letter of the data table address is a T C or P but there are not 4 characters in the specification Incorrect addresses that would cause this error include C 15 C5 3 CCUM 23 etc 2 The key data table word specifier was 4 characters long and began with a T C or P but it did not match the legal word specifiers e g STACM 3 3 There was no colon following a legal word specifier Missing colon between file and word 7 11 Chapter 7 Error Reporting EXT STS Code STS Code if applicable if applicable 164 165 166 169 171 177 178 179 188 189 192 194 199 200 201 202 203 204 205 206 7 12 Illegal word specifier a data table address Illegal context specifier When an expression determined the context ina data table address or when the global context context 0 was specified data table address a colon followed the context Attempt to execute a symbol not defined as a process The system symbol exists but refers to a symbolic address rather than to a pro cess Either the number or the expression following the an address has a value outside the range 0 to 15 decimal Value specified in a bit assignment statement was other than a zero or
199. ts access is limited by memory access rungs in the communication zone of the PC s ladder diagram program The data field in this packet consists of 4 byte blocks each of which contains a 16 bit address field a set mask and a reset mask Use the ADDR field to specify the address of the byte to be modified in the PC data table memory Put the low byte least significant bits of the PC address value into the first byte of the ADDR field Refer to chapter 6 for more details on how to specify an address value Use the SET mask to specify which bits to set to 1 in the addressed PC byte A 1 in a bit position of the SET mask means to set the corresponding bit in the addressed PC byte to 1 a 0 in a bit position of the SET mask means to leave the corresponding bit in the PC byte unchanged Use the RESET mask to specify which bits to reset to 0 in the addressed PC byte A 1 in a bit position of the RESET mask means to reset the corresponding bit in the addressed PC byte to 0 a 0 in a bit position of the reset mask means to leave the corresponding bit in the PC byte unchanged Note that the interface module at the receiving PC station executes this command by first making a copy of the addressed PC byte It then sets or resets the appropriate bits and writes the byte back into PC memory At the same time the PC processor can be changing the states of the original bits in memory Because of this some data bits may unintentionally be overwritten C
200. unication Adapter Module cat 1775 KA PLC 4 Communication Interface Module cat no 1773 K A PC Processor RS 232 C Interface The following modules provide an interface between a PC processor and an RS 232 C communication link PLC 3 Communication Adapter Module cat 1775 KA PLC 4 Communication Interface Module cat no 1773 K A PLC 2 Family RS 232 C Interface Module cat no 1771 KG RS 232 C Data Highway Interface The following modules provide an interface between an RS 232 C communication link and a Data Highway communication link Communication Controller Module 1771 KC KD KE KF The 1771 KC and 1771 KE modules must be installed in an I O chassis The 1771 KD and 1771 KF modules are stand alone modules The 1771 KC and 1771 KD modules can provide peer to peer communication only through an RS 232 C link that cannot connect to a modem link They are superseded by the 1771 KE and 1771 KF modules that can provide either peer to peer or master slave communication through an RS 232 C link which you can optionally connect to a modem link Configuration Selection Figure 2 1 through Figure 2 4 illustrate several configurations in which PC stations can communicate with each other and with computers through Data Highway ports and RS 232 C ports on the station interface modules Each configuration is useful depending on your application If you want to provide a peer to peer communication between two
201. upts are off when they are called They will always return with interrupts off The interaction of SLEEP and WA KEUP When one process calls SLEEP the result is a return from a WAKEUP by another process When a process calls WAKEUP the result is a return from a call to SLEEP by another process Figure B 19 SLEEP and WAKEUP Interaction In the example in Figure B 18 A third alternative would cause a con Process B woke up Process A text switch of a process performed a some time ago Now at 1 when A WAKEUP on a higher priority process goes to sleep actual execution resumes If a WAKEUP was performed on a after the wakeup call in B at 3 and 4 lower priority process the context Sometime later process C at an switch would be deferred until the first interrupt for example calls WAKEUP at 5 Ex process went to SLEEP ecution flow proceeds to the instructions at 8 following the call to SLEEP in Process A The next time A calls SLEEP he WAKEUP call in C will The first alternative is the result An interrupt subroutine that calls WA KEUP is viewed as a subroutine of the interrupted process PROCESS A CO terminate of implementing the driver totally at yu interrupt level The third alternative E m possc would be used if the driver were im aie plemented as tasks under a multi tasking operating system Such Another implementation would allow implementation might be easier but a process to call WAK
202. vel noise on the highway It seems to be especially sensitive to problems on longer cables It will also appear often if the receiver or transmitter circuitry on a module is marginal or if the cable connections are loose Contentions Counts the number of times contention was detected This will also appears quickly on noisy or overlength cables This counter corresponds to error 93 Bad ACK status Counts the number of times the ACK was successfully received but contained a nonzero status code other than memory full Currently the only other implemented ACK code is buffer overflow This condition should never occur except possibly when debugging new computer programs Returned messages Counts the number of times the highway driver returns a message to sender Each count corresponds to one local error bit set or one reply message lost Transmit memory full Counts the number of times the highway driver returns a message to sender Each time this happens the message is placed on a waiting queue for a half second Each message will be re tried five times before it is returned to the sender 10 11 12 13 14 15 Chapter 7 Error Reporting Poll timeout Counts the number of times this station grabbed mastership of the highway because it timed out while waiting to hear a valid frame On a highway that has just been powered up there should be only one station that has this counter incremented False poll Counts the
203. ysical read or write command to a PLC station put the PLC physical address in the ADDR field of the command message format chapter 5 Be sure to encode the low byte of the physical address as the first byte in the ADDR field PLC 2 PLC 2 controllers use physical addresses that are directly related to the logical addresses To convert a given logical address to its corresponding physical address move bit 7 of the logical address to bit position 1 and shift bits 1 through 6 to the left one position Figure 6 8 illustrates the conversion process for logical word address 121 Remember that the logical PLC 2 address is a byte address so the physical address will also be a byte address Figure 6 8 Converting PLC 2 Logical to Physical Address PLC 2 Word Address 121 Octal Logical Byte Address 242 Octal Physical Byte Address 0046 Hex High Byte Low Byte 17 16 15 14 13 12 1 10 7 6 5 4 3 2 1 0 0 0 0 0 0 0 0 0 1 0 1 0 0 0 1 0 0 0 0 0 0 0 0 0 0 1 0 0 0 14 1 0 11161 1 6 13 Chapter 6 Data Manipulation To send a physical read or write command to a PLC 2 station put the PLC 2 physical address in the ADDR field of the command message format chapter 5 Be sure to encode the low byte of the physical address as the first byte in the ADDR field PLC 3 PLC 3 controllers use physical addresses that are related to l

1771-6.5.15, Bulletin 1771 Communication Controller Module User

Contents

Download Pdf Manuals

Related Search

Related Contents