1761-6.5.27, Direct Communication Module User Manual
Contents
1. PLC 2 30 n o O GA de S s o D E Qu rand anu um i CCUG z jJ B E THEMEN CAH en en CAEN CI uL E T SEB ESIE MEME is s s nu E ENE LEPETERLET LET ELT ET ELELTIELHET 1771 ASB 1771 DCM Remote I O Chassis qo S gt zs 2 iu 3 c 3 i i H 1771 ASB IEDM Install Terminator Resistor cat no 1770 XF 12662 4 3 Using the Status Word Examining Status Bits Using the Status Word The 1771 DCM sets status alarm bits in the upper byte of the first word transferred to either processor regardless of whether you select block transfer or discrete data transfer In block transfer operation the status word is the first word of the2. 1 1 0 2 0 O chassis 2 0 0 n number of block tranfer modules in chassis 3 1 0 4 Make interactive thru processor LIST Description Number Ch 1 Ch2 Ch3 Ch4 Active I O channels 3 Block transfer I O channels 2 Block transfer modules on each 1 0 block transfer channel 3 0 1 0 I O chassis on each block transfer 1 0 channel I O chassis in rack list 4 0 2 0 12828 2 Using information from the diagram of I O channels Figure 7 1 look up the nominal time from the table in Figure 7 2 7 9 Chapter 7 Calculating Transfer Time Figure 7 2 Nominal Time Table Step 2 Determine a time from the table Example values have been added for a BTW instruction Number of Active I O Channels 1 21314 Number of active I O channels 3 1 45 50 60 65 Number of active I O channels containing one or Active I O channels more block transfer module 2 containing one or more 2 70 70 75 block transfer modules Time from table 70 ms 3 85 95 4 100 Time ms 12829 3 Compute the approximate transfer time for each block transfer I O channel Use values from your channel diagram Figure 7 1 a value from the table Figure 7 2 and the formula from Step 6 above We make these calculations for you in Figure 7 3 Figure 7 3 Computing Channel Times STEP 3 Compute the scanner time f
3. If a block transfer read instruction is enabled but the scanner s buffer cannot accept the instruction s block length the scanner is processing other blocks of data the block transfer instruction must wait for a subsequent scan when the scanner s buffer can accept all the words that the module has to transfer The same applies for a write block transfer instruction We suggest that you add an additional scanner if necessary Block Transfer Errors Once enabled a block transfer instruction in a PLC 3 ladder program will set either a done bit or an error bit The instruction indicates an error when it illuminates the ER symbol Typical block transfer errors occur when You do not correctly enter the instruction The rack group and module numbers do not match the location of the installed module You entered a file length greater than 64 You did not create the data file or the address that you entered does not match the file you created Read and write error bits illuminate at the same time when the error source is the module address entry or the file length entry in the instruction block Chapter 7 Calculating Transfer Time You have a communications problem You did not correctly connect the twin axial cable to the scanner You did not connect a terminator resistor to each end of the twin axial cable When the scanner encounters a communication fault it tries twice to complete the transfer It se
4. 1 Determine the number of active I O channels on the scanner 2 Determine the number of I O channels with block transfer modules 3 Use these tables to determine the nominal block transfer time using the numbers from Steps 1 and 2 Nominal Block Transfer Times ms for a BTW 3 Active Channels 2 70 70 75 3 85 95 4 a 100 Nominal Block Transfer Times ms for a BTR 3 Active Channels 2 60 60 65 3 70 80 4 90 Block transfer times typically are similar regardless of the type of block transfer module or the number of words transferred Nominal read block transfer times typically are faster than nominal write block transfer times by approximately 10 ms In this example consider them the same 7 7 Chapter 7 Calculating Transfer Time 7 8 4 Count the number of block transfer modules on the channel If a chassis containing block transfer modules is repeated in the rack list count chassis and modules as often as listed 5 Count the number of I O chassis entries in the rack list for the channel 6 Calculate the block transfer time for the scanner as follows Scanner _ Nominal x 4 BT Modules a 10 Chassis 1 x 9ms Time Time on the Channel in Rack List PLC 3 Example Computation As an example we will compute the read or write block transfer time between the supervisory processor and a 1771 DCM in an I O channel with no other block transfer modules and i
5. Local 82 5 ms 15 ms 31 6 ms 129 ms Solution Part 2 Additional time for two block transfer modules in the local chassis Time PLC 2 05 2 0 08 ms x Number of Words Transferred 2 0 08 ms 64 1 10 2 ms Total Transfer Time Discrete Transfer Block Transfer 129 ms 10 2 ms 139 ms Worst Case When you select block transfer as the mode of transfer between the supervisory processor and 1771 DCM you can transfer up to 64 words but the transfer time increases The time required for the transfer of data from supervisory to local processor and vice versa is the sum of three events Supervisory Processor and Remote I O Scan Time Transfer Time through the 1771 DCM Local Processor Scan Time 1771 DCM and Local Processor Refer to Discrete Data Transfer above for the time required by the 1771 DCM and the local processor These times are the same for either method of transfer between the supervisory processor and the 1771 DCM Chapter 7 Calculating Transfer Time PLC 2 Family Supervisory Processor The time required by the supervisory processor is the sum of the program scan processor I O scan and remote I O scan The time is lengthened by the number of enabled block transfer modules transferring data one module after the other and on the number of words that each module transfers Calculate the time for a read or write operation for each enabled block transfer module as follows PLC 2 3
6. Ty Allen Bradley Direct Communication User Module M anu al Cat No 1771 DCM Table of Contents To Our Customers Lsuueeues 1 1 To Qur GUslolmels 12 2 dde ken ELiYwEEPERSEd i3 seedy es 1 1 Manual s Purpose 00 0 cece eee eee I 1 1 Intended Audience 0 2 06 cisci 1 1 Terminology orerar adere cc E IRI 1 1 Related Publications 22 rm 4 4 Overview of Direct Communication Module 2 1 Overview of Direct Communication Module 2 1 Describing the 1771 DCM 0 cece eee eens 2 1 Choosing 1771 DCM or Data Highway 0 2 2 Selecting Options 2 6 2 ence eee ete mm 2 2 Example Applications c 402 224 send ete meth seuss 2 3 Compatible Processors 2 cece cece eee ences 2 3 MCC HU ead 2 3 Selecting Options 222i rnm nn 3 1 Selecting Options ioris sili e Epp REX ees o RES 3 1 Switch Bank O orc ek a ede ERERQU PRESE MESSE See 3 2 Switch Bk 23 cond dts EDAD LETS SEA ER UI EAE 3 4 Connecting Cables LLuseses 4 1 Connecting Cables 0 00 c eee eee eee eee 41 Module Connector 00c cece ce eee eee eeees 4 1 Daisy Chain Hookup nananana anaana 4 2 Trunkline Dropline Hookup 0 00 c nnana eee eens 4 3 Using the Status Word LLsuuueeeee 5 1 Using the Status Word Luuuussluseseuseeesse
7. 06 Module Address 200 Block Length 00 File 0500 0577 120 DN 06 6 7 Chapter 6 Programming the 1771 DCM 6 8 Figure 6 5 Block Transfer Programming Example for PLC 3 Supervisory Processor BTR Done Bit WBO001 0000 BTR CNTL NAE i 4 E BLOCK XFER READ K m A Rack 002 Group 0 CNTL Module 0 Low F1 PN Data FB002 0000 Length 064 CNTL CNTL FB001 0000 ER Read Request 13 WB001 0000 BTW CNTL E BLOCK XFER WRITE F LE 17 Rack 002 02 Group 0 CNTL Module 0 Low DN Data FB003 0000 05 Length 064 CNTL CNTL FB001 0000 ER 03 BTR Done Bit WB001 0000 WB002 0000 MVF C0005 s F FILES FROM A TO R EN 15 10 12 Data Valid Bit File A FB002 0000 C0005 Buffer File File R FB004 0000 DN Counter C0005 15 Pos Len 0 64 C0005 Mode ALL SCAN ER 13 Rung 2 2 Figure 6 6 Chapter 6 Programming the 1771 DCM Block Transfer Programming Example for PLC 5 Family Supervisory Processor PLC5 supervisory write rung The DCM is connected via remote I O to the PLCS and is set for 57 6K baud block transfer and rack 3 The supervisory processor s write length must match the local processor s read length BTR BIW Rira BIT eae BIT BTW L Mt BLOCK TRNSFR WRITE ENH 15 15 Rack 3 Group 0 DN Module 0 Control Block N22 0 ER Data file N19 0 Length 31 Continuous N Rung 2 3 PLC5 supervisory read r
8. 22 ON OFF ON oN OFF JON 23 ON OFF ON ON OFF OFF 24 ON OFF ON OFF ON ON 25 ON OFF ON OFF ON OFF 26 ON OFF ON OFF OFF JON 27 ON OFF ON OFF OFF OFF 3 5 Chapter 3 Selecting Options 32 ON OFF OFF ON OFF ON 33 ON OFF OFF ON OFF OFF 34 ON OFF OFF OFF ON ON 35 ON OFF OFF OFF ON OFF 36 ON OFF OFF OFF OFF ON 37 ON OFF OFF OFF OFF OFF First Module Group Number 2 ON OFF 4 ON ON 6 OFF OFF Assign a unique stating module group number such as 0 2 4 or 6 in accordance with the number of chassis you assigned to the same I O rack number You can assign from one to four 1771 DCMs and I O adapters to the same I O rack number provided that the combination does not exceed a full rack For example assign starting module group numbers to each I O chassis or 1771 DCM in the following combinations Rack Configuration Assign Module Group Numbers e Four 1 4 Racks 0 2 4 and 6 e Two 1 2 Racks 0 and 4 e One 1 4 and One 3 4 Rack 0 and 2 e One 3 4 and One 1 4 Rack 0 and 6 You selected the equivalent rack size of your 1771 DCM with Switch Bank 0 Switches 7 and 8 above 3 6 Connecting Cables Module Connector Connecting Cables The communications channel between the 1771 DCM and a supervisory processor is the same serial communications channel as used between the 1771 ASB Remote I O Adapter
9. 5 1 Examining Status Bits 12e eo rb Re E eee 54 Status Bits Read by the Local Processor 5 2 Status Bits Read by the Supervisory Processor 5 3 Programming the 1771 DCM 6 1 Programming the 1771 DCM lsussllseeeesee 6 1 Local Processor Logic 00 ccc cece eee 6 1 1771 DCM Switch Settings ccc eee eee 6 3 Supervisory Processor Logic 0c cece cence 6 3 Processor Module Compatibility esses 6 13 Table of Contents Calculating Transfer Time Calculating Transfer Time 000 cece eee eee eee Discrete Transfer Time 2 2 0 6c e eee eee eee eee eee Block Transfer Time c2ces8iwavewsdwioeeds e sae ees Block Transfer with a PLC 3 Supervisory Processor Troubleshooting Your 1771 DCM Troubleshooting Your 1771 DCM Lsseuuessee LED Display for Normal Operation llluussuse LED Display for Fault Conditions lesus Causes of Block Transfer Errors 0 0 c eee eee eee Errors Indicated by Status Bits 000 2 eee SPOCMCMIONS s ace pet PEERS PEE dus de oe obec Geos N LI LN T rk AB Pe Li T m E ke n2 EE AC To Our Customers Manual s Purpose Intended Audience Terminology Related Publications To Our Cu
10. 5 ms K Words 2 5 ms K Words Processor I O 0 5 ms Rack N A Remote I O 7 ms Chassis 6 ms Chassis 7 1 Chapter 7 Calculating Transfer Time 7 2 Total Scan PLC 2 Program Processor I O Remote I O Total Scan PLC 3 Program Remote I O 1771 DCM The delay from the time the 1771 DCM receives data until it is ready for data transfer is 15 ms During this time it detects errors and changes in status and formats data Local Processor The local processor reads data from or writes data to the 1771 DCM using block transfer instructions regardless of how data is transferred between 1771 DCM and supervisory processor The time required is equal to the program scan plus block transfer time which depends on the number of words transferred PLC 2 05 PLC 2 15 PLC 2 30 Local Program Scan 15 ms K 18 ms K 5 ms K 1 0 Scan 1ms 4ms 0 7 ms Block Transfer 0 08 ms W 0 08 ms W 0 08 ms W W Number of Words Transferred Total Scan Program and I O Scan Multiplier x Number of Words Transferred See the appropriate processor manual for times for other processors Addition of Block Transfer Modules Block transfer modules in the local I O chassis can lengthen the I O scan time by the time required for each to perform a block transfer worst case The delay depends on the number of block transfer modules waiting to transfer and the number of words each will transfer Calculate the additional block transfer time fo
11. Calculating Transfer Time Discrete Transfer Time Calculating Transfer Time The time required for the transfer of data from supervisory to local processor and vice versa is the sum of three events Supervisory Processor and Remote I O Scan Time Transfer Time through the 1771 DCM Local Processor Scan Time The time required for the supervisory processor to communicate with the 1771 DCM depends on whether you select discrete data transfer up to eight words or block transfer up to 64 words the number of other remote I O chassis and the number of block transfer modules in the local and remote I O systems You select the mode of transfer between the supervisory processor and the 1771 DCM as either discrete data transfer or block transfer Discrete data transfer is faster than block transfer Calculate the transfer time between processors when the 1771 DCM is transferring discrete data by calculating the times associated with the supervisory processor 1771 DCM and the local processor Assume the supervisory and local processor systems contain no other block transfer modules Supervisory Processor The supervisory processor reads discrete input data or writes discrete output data to from its I O through its remote I O scanner Calculate the total scan time of the supervisory processor as the sum of the program scan processor I O scan if applicable and the remote I O scan using values in the table as follows Program
12. Series A and the scanner of a supervisory processor You insert the 1771 DCM in a local or remote I O chassis and configure the 1771 DCM as an I O chassis unique to the supervisory processor You can connect the 1771 DCM in a daisy chain or trunkline dropline hookup with other remote I O chassis Make your connections to the connector at the bottom of the module Figure 4 1 Connector terminals are labeled at the bottom of the left cover plate Connector terminals accommodate two cables one for the incoming line of a daisy chain hookup the other for the outgoing line Use either set of connector terminals for the dropline in the trunkline dropline hookup Terminal 1 is connected to Terminal 4 Terminal 2 to Terminal 5 and Terminal 3 to Terminal 6 inside the 1771 DCM WARNING Do not disconnect this connector in a daisy chain hookup when the system is operating because you disconnect the remaining I O chassis in the daisy chain The connection between terminals is inside the 1771 DCM Figure 4 1 Cable Connections Line2 Clear wees I 1 1 0 Cable Shield amp ee 2 Line1 Blue amp Lori Line2 Clear S PONES amp Shield Linea ss S MU LIC day Gran Connector on 1771 DCM Mating Connector roe 4 1 Chapter 4 Connecting Cables Daisy Chain Hookup 4 2 When using the daisy chain hookup Figure 4 2 splice each I O chassis into the main communicati
13. adequate in addition to the transfer time of the local processor and 1771 DCM Decrease data highway traffic At least one processor must have a remote I O scanner You cannot transfer ladder diagram programs nor messages stored in the message area of memory using the 1771 DCM You can select one or more of the following options depending on your application requirements using switches on the module Example Applications Compatible Processors Keying Chapter 2 Overview of Direct Communication Module Baud Rate Distance Select the communication rate and distance to the supervisory proces sor as either 57 6K baud to a distance of 10 000 feet or 115 2K baud to a distance of 5 000 feet Transfer Method Select block transfer or discrete data transfer between the 1771 DCM and the supervisory processor Rack Size When using discrete data transfer select the number of slots that de termines how the 1771 DCM appears to the scanner of the superviso ry processor the size of the I O chassis simulated by the 1771 DCM This also determines the number of words transferred Protected Data Select protected data to prevent block transfers from the local proces sor until the supervisory processor has received the previous block transfer I O Rack Address Designate the I O rack number the number of the first module group of the I O chassis simulated by the 1771 DCM and whether it has the highest starting module group address o
14. data transfer only Switch Bank 0 Switches 7 and 8 The equivalent rack size for block transfer mode is fixed at 1 4 rack Discrete Data Transfer The supervisory processor transfers discrete data to and from the 1771 DCM automatically via its I O scan You do not program these transfers To transfer discrete data words to and from the 1771 DCM you must use I O image table addresses in the supervisory processor s ladder program starting with the addresses RGS to which you configured your 1771 DCM Use the number of image table words equal to the equivalent I O rack size that you set for the 1771 DCM The ladder program of your supervisory processor must move discrete data read from the 1771 DCM from input image table words to a storage location Figure 6 3 64 Figure 6 3 Supervisory Processor Programming Example for Discrete Data Transfer PLC 2 30 FFM Done Bit T 0041 t ya Data Valid Bit FILE TO FILE MOVE Len Counter Address 0041 15 10 a 17 Position 001 Buffer File File Length 008 0041 File A 0120 0127 DN File R 0700 0707 15 Rate per Scan 008 Your ladder program must place data into output image table words for transfer to the 1771 DCM Avoid placing data in the first word because the 1771 DCM inserts status in this word We leave this ladder logic to you because your application and processor s set of instructions determine how you would do this Chapte
15. read data block In discrete data transfer the status word is found in the equivalent of the first module group of the I O chassis simulated by the 1771 DCM Important Reserve the first transferred word for status data inserted by the 1771 DCM Be sure this word contains zeros when you initialize the ladder program for either processor The upper byte contains status data The lower byte is not available for transferring data under any circumstances When you select discrete data transfer and set your rack size for the number of words required for your application keep in mind that the number of words available for your data is one less than the number of words transferred Number of Words Available Rack Size Transfer Words For Your Data 3 4 6 5 Examine bits in the upper byte of the status word using your ladder program so it can take appropriate action when the 1771 DCM detects an error or change in status Upon detecting an error or change in status the 1771 DCM sets an invalid data bit along with one or more bits that indicate the nature of the error or change in status These bits are non retentive 5 1 Chapter 5 Using the Status Word Status Bits Read by the Local Processor 5 2 Bits in the status word read by the supervisory processor differ from those read by the local processor Some bits apply only when the 1771 DCM is communicating with the supervisory processor by block transfer When the 1771 DCM detec
16. 0 Program 5 ms K Words Processor I O 0 5 ms Rack Remote I O 7 ms Chassis Time 1 Module Program Processor I O 2 Remote I O 0 5W 10 Where W number of words transferred and 10 is an average constant typically this constant is 4 for a read and 13 for a write If it is possible that all block transfer modules in the supervisory system could be enabled at the same time the worst case time for any one transfer would include the waiting time for all other other block transfers PLC 2 Family Example Computation Suppose there are four block transfer modules in addition to the 1771 DCM that could be enabled simultaneously in a PLC 2 30 supervisory system The local system has no additional block transfer modules Assume that the program has 4 8K words there are six assigned rack numbers in the remote I O link and that each block transfer is 64 words 1 Calculate the worst case time for the five modules to block transfer their data 2 Calculate the worst case time for a block transfer from the supervisory to the local processor 7 5 Chapter 7 Calculating Transfer Time Block Transfer with a PLC 3 Supervisory Processor 7 6 Solution Part 1 Time 1 Module 5 ms 4 8 0 5 ms 6 2 7 ms 6 0 5 64 10 24 ms 3 ms 84 ms 32 ms 10 ms 153 ms Total Time All Five Modules 5 153 765 ms Worst Case Solution Part 2 To calculate the worst case time for block transfer
17. 1 DCM SER COM Supervisory processor is in program or test mode Check mode selection Supervisory processor is not connected to the scanner Check the cable between processor and scanner PLC 2 30 proces sor Supervisory processor detected a fault and turned off outputs Check processor LEDs and status of outputs OFF 8 1 ET Cla Troubleshooting Your 1771 DCM Causes of Block Transfer Errors 8 2 Lum me 0 mem 000 BCKPLN The 1771 DCM turns on this LED for half a second at the com COM pletion of a read or write block transfer This LED blinks when e The local processor performs block transfers at a rate slower than once every 1 2 second With the 1771 DCM in protected data mode the supervisory processor performs block transfers at a rate slower than once every 1 2 second Reduce program scan and or I O scan time if possible in either processor OFF No block transfers are occurring across the backplane between the local processor and 1771 DCM Refer to Block Transfer Errors for the local processor below DCM FLT The 1771 DCM has detected an internal fault and is not operat ing Cycle power to the I O chassis containing the 1771 DCM Replace it if the LED remains lit when you restore power If the 1771 DCM is the only thing connected to a supervisory PLC 3 and the scanner baud is 115 2K the DCM will stop communicating and turn on the red fault light after approximate ly 20 minutes of communication Observe bl
18. 1771 DCM into Words 600 through 677 277 200 Status Word Zeroed 600 Status Word Inserted by DCM 201 First Data Word 601 First Data Word 202 Second Data Word _ 602 Second Data Word 277 Last Data Word 677 Last Data Word 6 12 Chapter 6 Programming the 1771 DCM Processor Module Compatibility Your 1771 DCM must have the following revision or later for compatible block transfer operation with your processor Processor Family 1771 DCM Revision PLC 5 250 Data transfers would occur as follows when the supervisory processor is a PLC 3 Supervisory Processor To Local Processor BTW Instruction Writes Data to the BTR Instruction Reads Data from the 1771 DCM 1771 DCM from Binary File 3 Words into Words 300 through 377 0 through 63 FB003 0000 Status Word Zeroed 300 Status Word Inserted by DCM FB003 0001 First Data Word gt 301 First Data Word FB003 0002 Second Data Word gt 302 Second Data Word FB003 0063 Last Data Word ___ 377 Last Data Word Local Processor To Supervisory Processor BTW Instruction Writes Data to the BTR Instruction Reads Data from the 1771 DCM 1771 DCM from Words into Binary File 2 Words 0 through 63 200 through 277 200 Status Word Zeroed FB002 0000 Status Word Inserted by DCM 201 First Data Word gt FB002 0001 First Data Word 202 Second Data Word v FB002 0002 Second Data Word 277 Last Data Word FB002 0063 Last Data Word 6 13
19. B Ee R 1771 ASB 1771 DCM Remote I O Chassis 1771 ASB ld dr SEE n FESTIS B E f E V A 7 i me Clear f 2 1 3 istor Shield Install Terminator Resistor Blue 1 Clear Shield 12661 Blue Chapter 4 Connecting Cables Trunkline Dropline Hookup When using the trunkline dropline hookup connect the 1771 DCM to the serial I O channel trunkline using a dropline that does not exceed 100 feet in length Figure 4 3 Connect the dropline to the trunkline using a T connector cat no 1770 XG or a station connector cat no 1770 SC There are no restrictions as to the spacing between station connectors or T connectors if you do not exceed the maximum cable distance Terminate the open port at the first and last T connector or station connector using a Terminator Set cat no 1770 XF Figure 4 3 Example Trunkline Dropline Hookup with T Connectors Shield
20. EN Rack 007 Group 0 DN Module 0 Control Block BR070 0 ER Data file 1BTD3 1 Length 15 Continuous NO BT Timeout 4 Chapter 6 Programming the 1771 DCM BTR BTW Module Address The module address of BTR and BTW instructions in the supervisory processor s program is the configured address of the 1771 DCM It is the I O rack number and starting module group number its slot number is always zero for block transfer that you set using Switch Banks 0 and 1 Block Length File Length Generally set them to the number of words that you set for the 1771 DCM If you have reason to set the read block length different from the write block length PLC 2 family processors be sure that both the BTR and BTW instructions cannot be enabled in the same scan When moving or transferring words into the BTW file for transfer to the 1771 DCM be sure to avoid placing data in the first word because the 1771 DCM inserts status in this word File to File Move FFM or MVF Use this instruction to store data received from the 1771 DCM File A address of the FFM or MVF is the same as the BTR file address File R address of the FFM or MVF is a storage file for data from the 1771 DCM Your ladder program for the supervisory processor must place data into the BTW file for transfer to the 1771 DCM We leave this ladder logic to you because your application and processor s set of instructions determine how you would do this Exa
21. ata table values such as command bits status bits and data blocks between supervisory and local processors The supervisory processor typically writes commands and or data table values to the local processor and reads resulting status diagnostic data and data values from the local processor or vice versa The supervisory processor communicates serially with the 1771 DCM as though it were a 1771 ASB Adapter Module and addresses the 1771 DCM as though it were addressing a separate I O chassis You select the mode of transfer between the supervisory processor and 1771 DCM discrete transfer up to eight words or block transfer up to 64 words Either mode includes one status word The local processor communicates with the 1771 DCM over the backplane using block transfers and addresses the 1771 DCM as an intelligent I O module When the local processor is remotely configured it communicates with the 1771 DCM via block transfer through its scanner adapter link The 1771 DCM and data highway allow communication between PC processors Consider the following factors when determining the appropriate choice Use the 1771 DCM to Transfer data table words Obtain predictable transfer times Transfer up to eight words when transfer time over a remote I O channel is adequate in addition to the transfer time of the local processor and 1771 DCM Transfer up to 64 words when transfer time for block transfers over a remote I O channel is
22. blocks and that you can manipulate data to and from these data blocks We will confine this discussion to programming characteristics unique to the 1771 DCM The local processor typically a PLC 2 family mini processor or PLC 5 family processor reads and writes data to the 1771 DCM using block transfers Programming examples Figure 6 1 Figure 6 2 assume that the 1771 DCM is set for six word block transfers Figure 6 1 Local Processor Programming Example PLC 2 013 BLOCK XFER READ EN Data Address 0030 17 Module Address 131 113 Block Length 06 DN File 0300 0305 47 BTR Done Bit 0040 ae Wil FILE TO FILE MOVE RENS j t 17 10 Counter Address 0040 17 Data Valid Bit eee 1 001 040 Buffer File lle Length 006 File A 0300 0305 Bos File R 0400 0405 Rate per Scan 006 BLOCK XFER WRITE de EN Data Address 0031 i 16 n Module Address 131 113 Block Length 06 DN File 0200 0205 16 6 1 Chapter 6 Programming the 1771 DCM 6 2 Block Transfer and File Move Instructions Enter these instructions using the following information BTR BTW Module Address The module address of BTR and BTW instructions in the local processor s program is the physical location of the 1771 DCM It is the I O rack module group and slot number RGS of the 1771 DCM In the same I O chassis with the local processor In an I O chassis connected to a processor configured fo
23. ce data in output image table word addresses for transfer to the 1771 DCM and move data from input image table word addresses as needed by your application We leave this ladder logic to you because your application and processor s set of instructions determine how you would do this Block Transfer We present block transfer rungs for the supervisory processor when the 1771 DCM is operating in block transfer mode Figure 6 4 for a PLC 2 30 supervisory processor Figure 6 5 for PLC 3 and Figure 6 6 for a PLC 5 family processor Chapter 6 Programming the 1771 DCM Figure 6 4 Block Transfer Programming Example for PLC 2 Family Local and Supervisory Processor LOCAL PROCESSOR BLOCK XFER READ Data Address 0030 Module Address 131 Block Length 00 File 0300 0377 BTR Done Bit 113 300 FILE TO FILE MOVE 17 10 Counter Address 0040 Data Valid Bit Position 001 Buffer File File Length 064 File A 0300 0377 File R 0400 0477 Rate per Scan 064 BLOCK XFER WRITE Data Address 0031 Module Address 131 Block Length 00 File 0200 0277 SUPERVISORY PROCESSOR BLOCK XFER READ Data Address 0032 Module Address Block Length 00 File 0600 0677 BTR Done Bit 0042 120 600 FILE TO FILE MOVE EN 07 10 Counter Address 0042 17 Data Valid Bit Position 001 Buffer File File Length 064 0042 File A 0600 0677 DN File R 0700 0777 15 Rate per Scan 064 BLOCK XFER WRITE En Data Address 0033
24. ckplane when switched to program test mode or when it detects a fault condition and turns off outputs The 1771 DCM cannot detect a backplane reset due to a fault condition resulting in outputs remaining in last state You determine the last state condition hold last state or turn off by a DIP switch on the I O chassis 5 3 Chapter 5 Using the Status Word 5 4 Bit 14 Backplane Error Set by the 1771 DCM whenever it detects that a block transfer operation by the local processor was not completed on time was out of sequence or contained a checksum error The 1771 DCM returns the last valid data received from the local processor It returns zeroed data words if communications had not been established It inhibits block transfers to the local processor until it detects a backplane reset or a scan from the local processor Bit 12 Old Data Set by the 1771 DCM whenever it detects that it has not received data from the local processor after a delay of 14 read scans by the supervisory processor discrete data transfer or since the last read block transfer by the supervisory processor The 1771 DCM passes old data to the supervisory processor until it detects new data passes it and resets this bit Bit 11 Not Used Programming the 1771 DCM Local Processor Logic Programming the 1771 DCM We assume that you are familiar with block transfer programming that you can allocate data table areas for read and write data
25. er read by supervisory processor 8 3 Chapter 8 Troubleshooting Your 1771 DCM Specifications 8 4 Function e Provides Direct Communication Between Supervisory and Local Processors Serial Communication e Discrete Data Transfer Up to Seven Words Plus One Status Word e Block Transfer Up to 63 Words Plus One Status Word Transmission e 10 000 Cable Feet at 57 6K Baud e 5 000 Cable Feet at 115 2K Baud Response Time e Less than 15 ms Interconnect Cable e 1770 CD Belden 9463 or Equivalent Backplane Current e 12A Keying e Top Connector Between 2 and 4 Between 16 and 18 Environmental e Operational Temperature 0 to 60 C 32 to 140 F e Storage Temperature 40 to 85 C 40 to 185 F e Relative Humidity 5 to 95 Without Condensation A Application Examples 2 3 Audience 1 1 Baud Rate 3 2 Block Length 6 2 6 11 Block Transfer 6 6 Errors Causes of 8 2 C Connections to Module 4 1 D Data Highway 2 2 Data Transfer Block Transfer Example 6 12 Discrete Data Example 6 4 Data Words Available 5 1 Description of 1771 DCM 2 1 Discrete Data Transfer 7 1 E Errors Indicated by Status Bits 8 3 Instructions Block Transfer 6 2 File Move 6 2 6 11 K Keying 2 3 L LED Displays 8 1 M Module Address 6 2 6 11 Index Module Group Number 3 6 0 Options Selection of 2 2 3 1 1 Overview of 1771 DCM 2 P Process
26. f two or more chassis as signed to the same rack address These options are described in Chapter 3 You can use the 1771 DCM in a variety of applications where the transfer of data table values is required For example consider using it to Call messages stored in the data table of the supervisory processor and outputted through an ASCII I O module cat no 1771 DA or BASIC module cat no 1771 DB Download recipe data table values from supervisory to local processor s where you want local processor s to execute different versions of the same program Download commands from the supervisory processor to execute different sections of a ladder diagram program at the local processor Use the 1771 DCM with any Allen Bradley programmable controller that uses block transfer and the 1771 I O structure Reserve an I O slot for this module by placing keying bands on the backplane connector Position keying bands between the following numbers labeled on the backplane adjacent to the upper backplane connector The keying bands mate with corresponding slots in the module connector Between 2 and 4 Between 16 and 18 2 3 Selecting Options Selecting Options Select one or more of the following options depending on your application requirements Do this by setting switches in Switch Banks 0 and 1 on the left metal cover side of the 1771 DCM To assist you we have printed a table of switch settings for each switch bank on the
27. from supervisory to local processor via the 1771 DCM add times for the 1771 DCM and local processor 15 ms and 31 6 ms respectively assuming no other block transfer modules in the local chassis Total Time 765 ms 15 ms 31 ms 811 ms The time required to complete a read or write block transfer depends on factors that include the number of Words of user program Active I O channels on the scanner O chassis entries in the rack list for the channel O channels on the scanner that contain block transfer modules Block transfer modules on the channel if the I O chassis containing a block transfer module appears more than once in the I O chassis rack list count the module once each time the chassis appears in the rack list Typical time required to complete a read or write block transfer depends on the program scan and the scanner scan as follows Time Read or Write Program Scan 2 Scanner Scan Program Scan The program scan is approximately 2 5 ms per 1K words of user program when using a mix of examine ON OFF and block instructions Chapter 7 Calculating Transfer Time Scanner Scan The time required for the scanner to complete a read or write block transfer depends on the number of other block transfer modules on the same scanner channel that are enabled simultaneously Use the following procedure to calculate the time required for the PLC 3 processor to perform all block transfers on the channel
28. gram executes block transfers Communication between the 1771 DCM and local processor is always block transfer regardless of the mode of communication between 1771 DCM and supervisory processor Switch 5 Not Used Switch 6 Protected Data ON Closed for Unprotected Data OFF Open for Protected Data This option maintains data integrity and maintains the order of data blocks sent from the local processor to the supervisory processor only when you select block transfer The 1771 DCM does not recognize the start of a 3 3 Chapter 3 Selecting Options Switch Bank 1 3 4 new write block transfer from the local processor until the supervisory processor has read the previous data from the 1771 DCM When you select unprotected data the local processor updates the 1771 DCM continually regardless of whether the supervisory processor has read the data from the 1771 DCM Switches 7 and 8 Rack Size a NN NN NN When your application requires the transmission of discrete data words the 1771 DCM appears to the scanner of the supervisory processor as a 4 8 12 or 16 slot remote I O chassis for the transfer of either 2 4 6 or 8 words respectively Select the equivalent rack size depending on the number of words of discrete data you want to write or read One slot is equivalent to eight discrete data bits One module group is equivalent to a word A full rack is equivalent to eight data words The 1771 DCM inserts
29. he last data received from the scanner or zeroed data words if communications had not been established The 1771 DCM turns off the serial communications LED until communications are restored Status Bits Read by the Supervisory Processor Chapter 5 Using the Status Word Bit 14 Not Used Bit 13 No Data Available Set by the 1771 DCM at power up The 1771 DCM rests this bit when it receives data from the supervisory processor Bit 12 Not Used Bit 11 Inhibit Outputs Set by the 1771 DCM to inform the local processor that the supervisory processor has been switched to program or test mode has switched itself to program mode because of a dependent I O fault PLC 2 family or that the 1771 DCM has lost communication with the supervisory processor Bit 10 Invalid Data Set by the 1771 DCM whenever it sets any other status bit As long as this bit is reset the 1771 DCM has detected no error condition or change in status When the 1771 DCM detects an error in its communication with the local processor it indicates this condition in the status word read by the supervisory processor as follows 17 16 15 12 10 Insuf Excess Backplane Backplane Invalid Data Data Reset Error Data Data Data Bits 17 16 13 and 10 Same as Local Processor Bit 15 Backplane Reset Set by the 1771 DCM to inform the supervisory processor that the local processor has reset the backplane The local processor typically resets the ba
30. ller Terms PCGI 7 2 PLC 2 05 Programming Manual 1772 6 8 6 PLC 2 15 Programming Manual 1772 6 8 2 PLC 2 02 2 16 2 17 User s Manual 1772 6 5 8 PLC 2 30 Programming Manual 1772 6 8 3 PLC 3 Programming Manual 1775 6 4 1 PLC 5 Family Processor Manual 1785 6 8 2 PLC 5 250 Programmer s Manual 5000 6 4 1 Overview of Direct Communication Module Overview of Direct Allen Bradley has introduced the Direct Communication Module cat no Communication Module 1771 DCM to meet the growing need for communication between PC processors Describing the 1771 DCM The 1771 DCM is a chassis mounted single slot I O module that allows communication between a supervisory processor and local processors Figure 2 1 The local processor can be chassis mounted or configured as a local or remote system Figure 2 1 Local and Remote Configurations Local Configuration Supervisory Processor Bidirectional Block Transfer PLC 2 30 PLC 3 Family PLC 5 15 PLC 5 25 PLC 5 250 Remote I O Link 1771 ASB Protocol Remote Configuration Local Supervisory Processor Processor Bidirectional D PLC 2 30 Block Transfer PLC 2 30 i PLC 3 Family PLC 3 Family PLC 5 250 PLC 5 15 PLC 5 25 PLC 5 250 Remote I O Link Remote I O Link 1771 ASB Protocol 1771 ASB Protocol 12825 2 1 Chapter 2 Overview of Direct Communication Module Choosing 1771 DCM or Data Highway Selecting Options 2 2 The 1771 DCM passes d
31. mine the status word received from the 1771 DCM as a condition for using the read block transfer data Zero the status word at power up and be sure that your ladder program does not use this word for any other purpose 6 11 Chapter 6 Programming the 1771 DCM Example 2 Suppose you want to transfer 64 words and you have configured the 1771 DCM to simulate a block transfer module in Rack 2 First Module Group 0 Also suppose that the 1771 DCM is located in the same chassis with the local processor and that the 1771 DCM s actual location RGS is 131 In this example you allocated data blocks for block transfer as follows Refer to Figure 6 4 for PLC 2 30 or Figure 6 5 for PLC 3 Programming Data Block Supervisory Processor Local Processor Read 600 through 677 300 through 377 Write 500 through 577 200 through 277 Data transfers would occur as follows for PLC 2 family processors Supervisory Processor To Local Processor BTW Instruction Writes Data to the BTR Instruction Reads Data from the 1771 DCM from Words 500 through 1771 DCM into Words 300 through 377 577 500 Status Word Zeroed 300 Status Word Inserted by DCM 501 First Data Word 301 First Data Word 502 Second Data Word 302 Second Data Word 577 Last Data Word gt 377 Last Data Word Local Processor To Supervisory Processor BTW Instruction Writes Data to the BTR Instruction Reads Data from the 1771 DCM from Words 200 through
32. module s cover next to the switches Figure 3 1 Figure 3 1 Tables for Switch Settings BANK 0 sw sWliast SWirRANS SW SW pata SW nACK SWITCH BAUD RATE 1 2 lRACK 3 MTHD 4 s PTcT 6 SIZE 7 g zc W Not o NN so MB no no NO 115 2 Used yes DSCRT Used YES 1 2 3 4 FULL 1 BANK 1 B2 A 3 N 4 SWITCH FIRST SWITCH K15 1 0 RACK MODULE s NUMBER 1123 4 5 6 lanoup no 7 8 0 7 pri Prp o0 0 Li L 2L ot 2 m 3c e 02 4 B 2 55 8 6 A 3 6 04 N14 2L7 al os 06 007 07 8 2 10 7 5 11 0 12 13 p 14 L 15 C 16 _ 17 ON s cLosep Mill 22 OFF 23 OPEN 24 25 26 27 30 81 32 33 34 35 36 L 97 NOTE DO NOT USE OTHER SWITCH POSITIONS 17906 3 1 Chapter 3 Selecting Options Switch Bank 0 3 2 Each switch bank has eight switches Set each switch to the ON closed position by depressing the right hand side of the switch or to the OFF open position by depressing the left hand side of the switch Figure 3 2 Figure 3 2 Example Switch Bank Switches 1 and 3 are OFF open Shading represents the switch position o UU m zZ niii 12826 The options that you select with Switch Bank 0 are as follows Switch 1 Baud Rate ON Closed for 57 6K Baud OFF Open for 115 2K Baud Set
33. n an I O channel with two other block transfer modules in the following system User program contains 20K words Channel 1 contains four I O chassis with a total of three block transfer modules including one 1771 DCM Channel 2 contains two I O chassis with no block transfer modules Channel 3 contains two I O chassis with one 1771 DCM Channel 4 is made inactive through processor LIST You can compute the read or write block transfer times for the supervisory processor in this example in four steps Each of the following steps is explained by an accompanying figure Diagram the I O channels of your PLC system Figure 7 1 showing the number of Block transfer modules in each I O chassis Block transfer I O channels I O chassis entries in the rack list for each block transfer I O channel Active I O channels per scanner A block transfer I O channel is a channel that contains one or more block transfer modules located in any chassis connected to the channel Chapter 7 Calculating Transfer Time An I O chassis can appear more than once in a rack list of I O chassis Count it and the block transfer module s that it contains as often as it is listed Figure 7 1 Diagramming I O Channels Step 1 Diagram the chassis connected in series to each channel up to 4 of your scanner module Then fill in the information called fo below Example values have been added
34. ock transfer rungs in the ladder diagram program of the processor not performing block transfers You have a block transfer error when you observe one or both of the following The block transfer error bit is intensified PLC 3 processor Enable and done bits of block transfer instructions either do not intensify or remain intensified They should alternately turn ON intensify and turn OFF Block transfer errors are caused if one more more of the following are incorrect The 1771 DCM s location RGS in the local I O chassis must match the RGS of block transfer instructions in the local processor s ladder program The address of the I O chassis simulated by the 1771 DCM RGS must match the module address RGS of block transfer instructions in the supervisory processor s ladder program The block lengths of read and write block transfer instructions should be equal PLC 2 family processors or if different do not enable BTR and BTW instructions in the same scan Errors Indicated by Status Bits Chapter 8 Troubleshooting Your 1771 DCM You assigned valid areas of data table for read and write blocks For example if operating in discrete data transfer mode I O image table addresses of the supervisory processor s ladder program match the RGS to which you configured the 1771 DCM Your conditioning instructions in block transfer rungs allow the rungs to turn ON and OFF If using a PLC 2 30 supervi
35. on line serial I O channel Install a 150 ohm terminator resistor between the terminals of Lines 1 and 2 at the scanner and at the last hookup on the main communications line to terminate both ends of the line Figure 4 2 Example Daisy Chain Hookup Blue 1772 SD2 1 Shidd Blue i Blue e Stield Shed PLC 2 30 7 Clear Gear Clear 20 E Teu SoS SS SS o p s TER Bim d i ec He e OEE aos SS ER CER eR er eS rem cem en en 0 a 171 A
36. one status word in the transfer regardless of the equivalent rack size you select When you set the 1771 DCM for block transfer the 1771 DCM appears to the scanner of the supervisory processor as a block transfer module in the first module group of a four slot chassis 1 4 rack You can read and write up to 64 words including one status word Slots 1 through 3 are not used The options that you select with Switch Bank 1 are as follows Switches 1 through 6 I O Rack Number PLC 2 Family PLC 3 and PLC 5 250 PLC 5 15 PLC 5 25 1 7 0 thru 37 octal 1 7 Chapter 3 Selecting Options Designate the I O rack number that you assign to the 1771 DCM with Switches 1 6 of Switch Bank 1 Table 3 A Table 3 A I O Rack Number Selection for PLC 2 PLC 3 and PLC 5 Family Processors Switch I O Rack Number Octal ao a Bo f 5 6 1 0 ON ON ON ON ON ON P 2 1 ON Jon Jon ON ON _ OFF L 3 2 Se Jon Jon Jon fon forF Jon C 4 3 ON JON ON JON OFF OFF 5 4 amp eelon fon fon fore fon JON 2 6 5 ON ON Jon OFF ON OFF 7 6 ON ON Jon OFF OFF JON 7 ON ON ON OFF OFF_ OFF 10 ON ON OFF ON Jon ON 11 ON ON OFF ON ON OFF PLC 3 12 ON ON OFF ON OFF ON pigeon 13 Jon fon OFF jon OFF jor 14 ON ON OFF OFF ON ON 15 ON ON OFF OFF ON OFF 16 ON fon OFF OFF OFF oN 17 ON ON OFF OFF OFF OFF 20 ON OFF ON Jon Jon ON 21 ON OFF ON oN ON OFF
37. or each block transfer channel Example values have been added CT Channel Time cr Nominal BTModules VO Chassis 9ms Time _ onBT Channel onBT Channel C4 70ms x 3 41 x 9 ms 210ms 3x 9ms 237 ms CT2 Not a Block Transfer Channel CT3 70ms x 1 2 1 x 9ms 70 ms 9ms 79 ms CT4 Notan Active Channel 7 10 Chapter 7 Calculating Transfer Time 4 Compute the approximate read or write block transfer time for Channel and Channel 3 Figure 7 4 Figure 7 4 Computing Block Transfer for Each Channel STEP 4 Compute the read or write block transfer time Example values have been added Program Scan Time Program 25ms K Words x 20K Words 25msx20 50ms Scanner Scan Time Read or Write 237 ms for Channel 1 and 79 ms for Channel 3 from Step 3 Block Transfer Channel 1 Program Scan 2 Scanner Scan Time Per Channel 50 ms 2 237 ms 50 ms 474 ms 524 ms Channel 3 Program Scan 2 Scanner Scan 50 ms 2 79 ms 50 ms 158 ms 208 ms Reducing PLC 3 Scan Time Due to the asynchronous scan relationship between program and scanner and the serial operation of each channel in the scanner we suggest that you optimize the overall scan time Although recommendations are application dependent we make the following recommendations as general guidelines Whenever possible control the manner in which block transfer instructions are enabled For example if onl
38. ors Compatible 2 3 Programming PLC 2 Family Processors Local Processor 6 1 Programming PLC 3 Supervisory Processor 6 1 6 3 6 4 6 7 6 8 6 9 6 10 Supervisory Processor 6 3 Protected Data 3 3 Publications Related 1 1 Purpose of Manual 1 1 R Rack Address 2 3 Number 3 4 Size 3 4 Rack Last 3 3 S Specifications 8 4 Status Bits 5 1 Status Word Read by Local Processor 5 2 Read by Supervisory Processor 5 3 Switch Bank Settings on 1771 DCM 3 2 6 3 T Terminator Resistor 4 2 4 3 Terminology 1 1 Timing Considerations PLC 3 Program Scan 7 6 Reducing Scan Time 7 11 Scanner Scan 7 7 Special 7 12 Index Transfer Method 3 3 Transfer Time Block Transfer _7 4 Example PLC 2 30 Supervisory Processor _7 5 Example PLC 3 Supervisory Processor 7 8 Transfer Time Discrete Data Transfer 7 1 Example PLC 2 Family Processors 7 3 Troubleshooting 8 1 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 and motion control devices operator interfaces sensors and a variety of software Rockwell is one of the worlds leading technology companies Worldwide representation aee M Argentina e Australia e Austria e Bah
39. r 6 Programming the 1771 DCM Example 1 Suppose you want to transfer six words and you have configured the 1771 DCM to simulate a 3 4 I O rack with the following address Rack Number 2 First Module Group 0 Also suppose that the 1771 DCM is located in the same chassis with the local processor that the 1771 DCM s actual location RGS is 131 that the local processor s block transfer read block is 300 through 305 and that the block transfer write block is 200 through 205 Data transfers would occur as follows Supervisory Processor To Local Processor Output Image Table Words Match the I O BTR Instruction Reads Data from the 1771 DCM Chassis Slots Simulated by the into Words 300 through 305 1771 DCM 020 Status Word Zeroed 300 Status Word Inserted by DCM 021 First Data Word gt 301 First Data Word 022 Second Data Word y 302 Second Data Word 025 Fifth Data Word 305 Fifth Data Word Local Processor To Supervisory Processor BTW Instruction Writes Data to the Input Image Table Words Match the I O Chassis 1771 DCM from Words 200 through Slots Simulated by the 1771 DCM 205 200 Status Word Zeroed 120 Status Word Inserted by DCM 201 First Data Word gt 121 First Data Word 202 Second Data Word 122 Second Data Word 205 Fifth Data Word gt 425 Fifth Data Word 6 5 Chapter 6 Programming the 1771 DCM 6 6 Your ladder program for the supervisory processor must pla
40. r local or remote I O operation Block Length File Length Generally set them to the number of words that you set for the 1771 DCM If you have reason to set the read block length different from the write block length PLC 2 family processors be sure that both the BTR and BTW instructions cannot be enabled in the same scan When moving or transferring words into the BTW file for transfer to the 1771 DCM be sure to avoid placing data in the first word because the 1771 DCM inserts status in this word File to File Move FFM Use this instruction to store data received from the 1771 DCM File A address of the FFM is the same as the BTR file address File R address is a storage file for data received from the 1771 DCM Your ladder program must place data into the BTW file for transfer to the 1771 DCM We leave this ladder logic to you because your application and processor s set of instructions determine how you would do this Examine the status word received from the 1771 DCM as a condition for using the read block transfer data Zero the status word at power up and be sure that your program does not use this word for any other purpose Rung 2 0 Chapter 6 Programming the 1771 DCM Figure 6 2 Local Processor Programming Example PLC 5 PLC5 local write rung The DCM is located in the same I O chassis as the PLC5 and is set for block transfer The local proces sor s write length must match the supervisory processor
41. r your processor as follows for each block transfer module Time Local Multiplier x Number of Words Transferred Chapter 7 Calculating Transfer Time PLC 2 05 2 15 0 08 PLC 2 30 Local 0 08 PLC 2 Family Example Computation Suppose that a PLC 2 30 supervisory processor has a 6K program and seven assigned rack numbers and the PLC 2 05 local processor has a 2K program There are no other block transfer modules in either the supervisory or local systems 1 Calculate the time required to transfer eight words from supervisory to local processor 2 Calculate the total time required if there are two additional block transfer modules in the local chassis transferring 64 words each Assume worst case Solution Part 1 PLC 2 30 Supervisory Processor Scan Time PLC 2 30 Program 5 ms K Words Processor I O 0 5 ms Rack Remote I O 7 ms Chassis Time PLC 2 30 Program Processor I O Remote I O 5 ms 6 0 5 ms 7 7 ms 7 30 ms 3 5 ms 49 ms 82 5 ms 1771 DCM Delay 15 ms Local Processor Scan Time Time for PLC 2 05 1 0 Scan 1 ms Program Scan 15 ms K Block Transfer 0 08 ms W 7 3 Chapter 7 Calculating Transfer Time Block Transfer Time 7 4 W Number of Words Transferred Scan Program Scan I O Scan Multiplier x Number of Words Transferred 15 ms 2 1 ms 0 08 8 ms 30 ms 1 ms 0 64 ms 31 6 ms Transfer Time Supervisory 1771 DCM
42. rain e Belgium Brazil e Bulgaria e Canada Chile e China PRC e Colombia e Costa Rica Croatia e Cyprus e Czech Republic e Denmark e Ecuador e Egypt e El Salvador Finland e France e Germany e Greece e Guatemala e Honduras e Hong Kong e Hungary e Iceland e India e Indonesia e Ireland e Israel Italy e Jamaica e Japan e Jordan Korea e 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 e Russia CIS e Saudi Arabia e Singapore e Slovakia e Slovenia e South Africa Republic e Spain e Sweden e Switzerland e Taiwan e Thailand e Turkey e United Arab Emirates e United Kingdom e United States e Uruguay e 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 27 October 1987 PN 955102 95 Supersedes 1771 6 5 27 June 1985 Copyright 1987 Allen Bradley Company Inc Printed in USA
43. s read length BTR BTW ENABLE BIT ENABLE BIT N12 0 N12 5 BTW J i E BLOCK TRNSFR WRITE ENH 15 15 Rack 0 Group 3 DN Module 1 Control Block N12 5 ER Data file N13 30 Length 17 Continuous N Rung 2 1 PLC5 local read rung The DCM is located in the same I O chassis as the PLC5 and is set for block transfer The local proces sor s read length must match the supervisory processor s write length 1771 DCM Switch Settings Supervisory Processor Logic BTR BIW ENABLE BIT ENABLE BIT BTR N12 0 N12 5 E E BLOCK TRNSFR READ EN 15 15 Rack 0 Group 3 DN Module 1 Control Block N12 0 ER Data file N13 30 Length 21 Continuous N Select module operating conditions by setting switches on the module for discrete data transfer or block transfer as follows Discrete Data Transfer Block Transfer e Transfer Method e Rack Size e Transfer Method e Data Protect If Applicable Set other switches as required by your application The addresses that you use for the 1771 DCM in the supervisory processor s ladder program are the addresses RGS to which you configure your 1771 DCM using Switch Banks 0 and 1 I O Rack Number Switch Bank 1 Switches 1 through 6 6 3 Chapter 6 Programming the 1771 DCM First Starting Module Group Number Switch Bank 1 Switches 7 and 8 The slot number will always be zero for block transfer only Equivalent rack size for discrete
44. sory processor set the scanner for block transfer operation If using a PLC 3 supervisory processor create block transfer data files Display status bits in the status word read by either processor by displaying the read block of the read block transfer instruction Refer to your processor s manual for the procedure The first word in the data block is the status word Hex codes of some typical fault conditions are tabulated below Hex Code Read by Local Processor 0300 2300 0900 or 2B00 4100 or 8100 Fault Condition Supervisory processor is in program or test mode No communication between the supervisory processor and its scanner 1771 DCM has not received data from the supervisory proces sor since power up Number of words transferred between the supervisory proces sor and 1771 DCM is not equal to the number read by the local processor Read by Supervisory Processor 0500 0900 or 0D00 1100 2300 4100 or 8100 1771 DCM has not received data from the local processor since the last time it was read by the supervisory processor 1771 DCM has not received data from the local processor since power up Local processor is not performing block transfers due to a time out out of sequence transfer or checksum error Local processor is not performing block transfers because it reset the backplane Number of words transferred between the local processor and 1771 DCM is not equal to the numb
45. stomers The following information may be helpful when using this manual The purpose of this manual is to help you understand the intended application of your Direct Communication Module cat no 1771 DCM and operate your 1771 DCM correctly in the shortest possible time We show you how to Select Module Options to Fit your Application Chapter 3 Install and Connect Your 1771 DCM Chapter 4 Use Status Bits to Detect Faults Chapter 5 Program the Transfer of Data between Processors Chapter 6 Compute the Transfer Time between Processors Chapter 7 Troubleshoot Module or System Malfunctions Chapter 8 We assume you are familiar with installing and using Allen Bradley programmable controllers and that you have written ladder diagram programs If not we suggest that you study the Programming and Operations Manual of your processor s listed below under Related Publications We have written this manual using current programmable controller terminology and have attempted to keep it free of jargon If you encounter terms that you do not understand we suggest that you obtain the current booklet Programmable Controller Terms listed below under Related Publications You should be able to install and operate your 1771 DCM without the need for additional publications If not the following publications may be of interest to you Chapter 1 To Our Customers Publication 1771 ASB Remote I O Adapter 1771 6 5 37 Programmable Contro
46. the baud rate equal to that of the scanner of your supervisory processor You can transmit data up to 10 000 feet at a data rate of 57 6K baud or up to 5 000 feet at a data rate of 115 2K baud Switch 2 Not Used Chapter 3 Selecting Options Switch 3 Last Rack ON Closed Not Last Rack OFF Open Last Rack If the 1771 DCM is assigned the same I O rack number as other I O chassis designate whether this I O chassis is the last chassis has the highest starting module group number of those assigned the same rack number Refer to I O Rack Number below Switch 4 Transfer Method ON Closed for Block Transfer OFF Open for Discrete Data Transfer Choose either discrete data transfer or block transfer between the supervisory processor and 1771 DCM With discrete transfer the rack size you select determines the number of words transferred as either 2 4 6 or 8 words including a status word Data is transferred between the 1771 DCM and the supervisory processor as serial remote I O data for each slot of the simulated I O chassis The supervisory processor updates the 1771 DCM as if it were an I O chassis on a remote I O link With block transfer you can transfer up to 64 words including a status word The 1771 DCM appears to the supervisory processor as a remote 1 4 rack Data is transferred between the first I O slot simulated by the 1771 DCM and the supervisory processor when the supervisory processor s ladder pro
47. ts an error in its communication with the supervisory processor it indicates this condition in the status word read by the local processor as follows 17 16 Insuf Excess Scanner Inhibit Invalid Data Data Comm Outputs Data Error Bit 17 Insufficient Data Available Set by the 1771 DCM when data received from the supervisory processor is less than that requested by the local processor It appends zeroed data words to provide the requested number of words Bit 16 Excessive Data Available Set by the 1771 DCM when the data received from the supervisory processor is more than that requested by the local processor It truncates the data and returns only the number of words requested Important In block transfer mode the 1771 DCM sets Bit 17 or 16 defined above when it detects that the length of a read block transfer request from one processor differs from the number of words previously written by the other processor In discrete data transfer the 1771 DCM sets Bit 17 or 16 when it detects that the number of words read by one processor differs from the number of words that the 1771 DCM temporarily stored This depends on the equivalent rack size that you set such as eight slots for four words Bit 15 Scanner Communications Error Set by the 1771 DCM when it detects a loss in communications with the scanner of the supervisory processor followed by a request for a read block transfer from the local processor The 1771 DCM returns t
48. ts the error bit after the second unsuccessful try When the scanner and or processor detects a block transfer error the transfer is halted Transfers from that module are prevented until Your program clears the instruction s control word clears the error Figure 7 5 You locate and correct the error Figure 7 5 Resetting the Control Word after a Block Transfer Error Control Word MOV Move from Ato R E 03 A Storage Word 0000000000000000 R Control Word f 0000000000000000 7 13 Troubleshooting Your 1771 DCM Troubleshooting Your 1771 DCM When troubleshooting your 1771 DCM check each of the following sources in the order given for the cause of the fault LEDs on the 1771 DCM Block transfer rungs in the ladder program of your local or supervisory processor Status bits in the status word read by the local or supervisory processor LED Display for Normal Under normal operating conditions the LEDs are lit as follows Operation Power PWR Serial Communication SER COM Backplane Communications BCKPLN COM Module Fault DCM FLT LED Display for Fault Conditions If a fault should occur the LED display changes to indicate the source of the fault which you diagnose as follows The 1771 DCM is not getting 5V DC Check the backplane power supply The supervisory processor is not communicating with the 1771 DCM Check cable connections in the remote I O link to the 177
49. ung The DCM is connected via remote I O to the PLC5 and is set for 57 6K baud block transfer and rack 3 The supervisory processor s read length must match the local processor s write length BTR BIW ENABLE BIT ENABLE BIT BTR N22 0 N22 5 E 1 BLOCK TRNSFR READ EN 15 15 Rack 3 Group 0 DN Module 0 Control Block N22 5 ER Data file N19 40 Length 27 Continuous N 6 9 Chapter 6 Programming the 1771 DCM Figure 6 7 Block Transfer Programming Example for PLC 5 250 Supervisory Processor Rung 1STEP0 0 PLC5 250 supervisory write rung The DCM is connected via remote I O to the PLC5 250 The DCM baud rate switch setting must match that of its scanner channel The DCM rack switches are set for rack 7 The local processor s read length must match the supervisory processor s write length 6 10 BTW BTR ENABLE BIT ENABLE BIT BTW BW070 0 BR070 0 TE BLOCK TRNSFR WRITE EN EN EN Rack 007 Group 0 DN Module 0 Control Block BW070 0 ER Data file 1BTD2 1 Length 17 Continuous NO BT Timeout 4 Rung 1STEP0 1 PLC5 250 supervisory read rung The DCM is connected via remote I O to the PLC5 250 The DCM baud rate switch setting must match that of its scanner channel The DCM rack switches are set for rack 7 The local processor s write length must match the supervisory processor s read length BTW BTR ENABLE BIT ENABLE BIT BW070 0 BRO70 0 BIR L BLOCK TRNSFR READ ENH EN
50. y a few block transfer modules require frequent transfer of data program them to run continually Inhibit block transfer instructions of those modules that require less frequent transfer until enabled by a timer and or some application dependent condition Program the read and write block transfer instructions of your 1771 DCM in the same rung Figure 6 5 Distribute your block transfer modules equally between all four scanner channels 7 11 Chapter 7 Calculating Transfer Time 7 12 Distribute block transfer instructions equally throughout your program Place an equal number of non block transfer rungs between block transfer rungs For large numbers of block transfer instructions distribute groups of block transfer rungs equally throughout your program Place no more than four block transfer rungs consecutively in one group Within each group condition the next rung using the done bit of the previous block transfer instruction Consider an additional I O scanner module cat no 1775 S4A if you cannot otherwise reduce the block transfer times to meet your timing requirements Special Timing Considerations When using one 1775 S4A I O scanner with thumbwheel switch set to 1 only part of its data handling capacity is available for handling block transfers This scanner can store and transfer a maximum of 72 words at any one time This scanner can do four block transfer modules across any of the active channels
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