B&B Electronics 485DSS User's Manual
Contents
1. 7 SG Signal Ground lt gt RS 422 485 Wiring RS 485 receivers also have an enable disable control line The 2W 4W jumper selects when to enable and disable RS 485 receiver Setting the jumper to the 4W position constantly enables the receiver which is the same as operating in an RS 422 485 4 wire mode In this position and connected to a 2 wire network all data being transmitted by the RS 485 driver echos back through the RS 485 receiver Setting the jumper to 2W RS 485 2 wire mode automatically enables the receiver when the RS 485 driver disables and visa versa To configure the 485DSS for a typical 2 wire party line network set the jumper in the 2W position Refer to Figure 2 for the jumper location The EIA RS 485 Specification labels data lines with an A and B designator Some RS 485 equipment uses a and designator In almost all cases the A line is the equivalent of the line and the B line is the equivalent of the line See Figure 3 for a wiring example 2 Wire Mode RS 485 allows half duplex communications of multiple drivers having a control line for enabling and disabling tri stating their outputs When the 485DSS transmits a status reply message to the Host the microcontroller will automatically enable the driver before transmitting the first character of the reply and disable the driver after the last character of the reply When the 485DSS is ON selected and the RS 232 device is tr2. Reply A 0 2 1 0 cr Reply A 0 3 0 0 cr Reply A 1 1 0 1 cr The reply indicates the following Unit 1 waited 40 milliseconds and then sent a reply indicating no connection of the RS 232 port to the network and the CTS handshake line is in the low state Unit 2 waited 60 milliseconds and then sent a reply indicating connection of the RS 232 port to the network and the CTS handshake line is in the low state Unit 3 waited 80 milliseconds and then sent a reply indicating no connection of the RS 232 port to the network and the CTS handshake line is in the low state Unit 17 decimal 11 hex waited 360 milliseconds and then sent a reply indicating no connection of the RS 232 port to the network and the CTS handshake line is in the high state 485DSS3298 Manual 13 B amp B Electronics PO Box 1040 Ottawa IL 61350 PH 815 433 5100 FAX 815 434 7094 If you were writing a program in BASIC to request status from address 5 decimal you might form a string like this DSSO5RS CHR 19 0 5 CHR 6 You could then send DSS05RS to request status from 485DSS address 5 Use similar strings for requesting status from other individual 485DSS s If you were writing a program in BASIC to request status from all the 485DSS s on the network you might form a string like this DSSALLRS CHR 19 CHR 18 CHR 18 CHR 6 Yo
3. ccccscssssssssscsscsssseseesessesessersesees C 1 CHART 1 IBM PC DB25 CONNECTOR TO occcccccccnnnconanononcnncnnnnnnnncnncnnns C 1 485DSS RS 232 DTE PORT cocccccoccccnononccononnnononnnancnnnnoconnnnononananonnno C 1 CHART 3 RS 232 DCE DEVICE W DB25 CONNECTOR TO 0000004 C 1 485DSS RS 232 DTE PORT cocccncoccccnononccononanonocancnccnonnaconannnononnnncnnns C 1 CHART 2 IBM PC DB9 CONNECTOR TO ooccnccccnccnnnnananononccnonnanononcncnnnns C 1 485DSS RS 232 DTE PORT sani aoet o a ea R S ees C 1 CHART 4 RS 232 DCE DEVICE W DB9 CONNECTOR TO C 2 485DSS RS 232 DTE PORT cocccncoccccnononcncnonancnocananccnonnonconnnccnonnnncnnns C 2 CHART 5 RS 422 485 4 WIRE DEVICE TO 485DSS RS 422 485PORT C 2 CHART 6 RS 485 2 WIRE DEVICE TO 485DSS RS 485 422 PORT C 2 Table of Contents 485DSS3298 Manual B amp B Electronics PO Box 1040 Ottawa IL 61350 PH 815 433 5100 FAX 815 434 7094 Chapter 1 HARDWARE Introduction The RS 485 Distributed Smart Switch 485DSS connects one RS 232 device to an RS 485 multi node network as shown in Figure 1 To accomplish this the 485DSS converts RS 232 to an addressable RS 485 node A unique address from 0 to 255 is user assigned by setting switches on the 485DSS Figure 1 Example of an RS 485 422 Multi Node Network Address 1 RS 485 2 Wire or RS 422 4 Wire 485155 B Address 2 RS 232 DEVICE ale Address 3 ADDRESTABLE RS 485 DEWICE Address 4 RS 232 485055 DEVI
4. ms R15 ohms C10 microfarads 38400 0 260 27K Factory Default 485DSS3298 Manual 5 B amp B Electronics PO Box 1040 Ottawa IL 61350 PH 815 433 5100 FAX 815 434 7094 HOST 485DSS TOCA TIBIA ROCA gt RDCBMC TOCBac 3 ROCA gt Emcee RDB Network SG GND TERM INK cor 2w IN O 4 Figure 3 RS 485 Wiring Diagram 4 Wire Mode To configure the 485DSS for RS 485 or 422 four wire mode place the jumper in the 4W position Refer to Figure 4 for connecting information and Figure 2 for the jumper location In this position on a 4 wire network the Host and the RS 232 device can communicate in full duplex CAUTION Data loss may occur if the Host sends 485DSS commands while the host is receiving data from the network 6 485DSS3298 Manual B amp B Electronics PO Box 1040 Ottawa IL 61350 PH 815 433 5100 FAX 815 434 7094 485DS RICA gt RDCB TICA TICE C SG GND TERM IN OUT ew O MN 44 485055 RICA RDCBC i SK TISH Network SG GND TERM INe O MB OUT 2 EO Figure 4 RS 422 Wiring Diagram RS 485 and RS 422 Termination A jumper labeled TERM provides termination for the RS 485 422 receiver The termination resistor is a 120 ohm resistor placed between the RD A and RD B lines To use this termination place the jumper in the IN position Refer to Figure 2 for the location of this jumper
5. character X off decimal 19 The second and third characters represent the hexadecimal address of an individual 485DSS The address range is from 0 to 255 HEX 00 to FF Some commands require the use of the broadcast character DC2 decimal 18 as the second and third characters in the command The fourth character is the command character Command Syntax X off Command character Least signf address character Most signf address character Start of message character ON Command This command turns on an individual 485DSS and asserts the RTS output handshake line on pin 4 of the DB25 connector This command allows the RS 232 device connected to the 485DSS to access the RS 485 network The address field in the command string specifies which 485DSS is to turn on All other 485DSS s on the network will turn off if the address field does not match their address setting Command character SOH decimal 1 Example 1 To turn on the 485DSS set to address 15 decimal OF hex HOST transmits Xoff 0 F SOH 19 48 70 1 decimal 13 30 46 1 hex Example 2 To turn on the 485DSS set to address 33 decimal 21 hex HOST transmits Xoff 2 1 SOH 19 50 49 1 decimal 13 32 31 1hex 10 485DSS3298 Manual B amp B Electronics PO Box 1040 Ottawa IL 61350 PH 815 433 5100 FAX 815 434 7094 If you were writing a program in BASIC to turn on address 10 decimal OA hexadeci
6. connects the RS 232 port to the RS 485 network Once ON selected the RS 232 device can transmit and receive data to the HOST Executing the OFF command lowers the RTS line disconnecting the RS 232 port from the network The RS 232 port of the 485DSS is OFF not selected at power up The 485DSS does not buffer or delay any data passing through the unit ALL data that is sent from the RS 485 device will be passed through to the RS 232 side while the unit is selected including the next set of command characters The Host can poll any or all 485DSS s on the network using the request status command This allows the Host to determine if any 485DSS is requesting access to the network by monitoring the handshake status character returned by the 485DSS The status character reflects the state of the input handshake signal Clear To Send CTS on the RS 232 connector pin 5 With this feature the Host has the ability to prioritize each 485DSS on the network Refer to Figure 2 8 485DSS3298 Manual B amp B Electronics PO Box 1040 Ottawa IL 61350 PH 815 433 5100 FAX 815 434 7094 RS 485 Port RS 232 Port So O i 1 FR cot io TD A D ee TD B RDIAJ D 2 RD B TD i EA OFF Microcontroller Address GND TL r Switch lt 5 CTS Figure 5 Simplified Functional Diagram Termination 2 gt 4 RTS Three red LED indicators are located on top of the 485DSS
7. 1 L m TERMINATION gt R18 R11 32Z 2 klas OU MN om m R17 MCM IN O O O OUT gt i RL Bez ali 51 OW AW a E De m D11 2W 000 4W Port Configuration The 485DSS has a RS 485 422 port and a RS 232 port The RS 485 422 signals are on terminal blocks Table 1 shows you the pinouts and Figure 2 shows you the location of the terminal blocks The RS 232 signal in the DTE configuration connects to a DB25 male connector Table 2 shows you the RS 232 pinouts RS 485 422 Port The RS 485 port on the 485DSS receives and transmits data to and from the RS 485 network The RS 485 port has a balanced differential line driver and receiver RS 485 allows up to 32 driver and receiver pairs to share a two wire party line network This port will operate on a 4 wire network and is compatible with RS 422 devices Refer to B amp B Electronics free RS 422 485 Application Note for more information Refer to Appendix C for cable charts 2 485DSS3298 Manual B amp B Electronics PO Box 1040 Ottawa IL 61350 PH 815 433 5100 FAX 815 434 7094 Table 1 RS 422 485 Port Terminal RS 422 485 Block Signal Signal Description Direction of Port TD A _ Transmit Data A RD A Receive Data A RS 232 Port The RS 232 DTE port is an asynchronous port that supports TD and RD signals In order to make the proper connections to the RS 232 port It is necessary to have a basic understa
8. 85DSS3298 Manual Appendix A B amp B Electronics PO Box 1040 Ottawa IL 61350 PH 815 433 5100 FAX 815 434 7094 Appendix B Decimal Hexadecimal Conversions The decimal base 10 numbering system represents each position in successive powers of 10 with each decimal symbol having a value from 0 to 9 The hexadecimal base 16 numbering system represents each position in successive powers of 16 with each hex symbol having a value of 0 to 15 Since each hex position must have a single symbol the symbols A through F are assigned to values 10 through 15 respectively Refer to Table 1 The information and examples to follow will explain how to convert from a decimal number to a hexadecimal number and vice versa Table 5 Dec Hex Conversions Decimal Hexadecimal Value Symbol ar po T 485DSS3298 Manual Appendix B B 1 B amp B Electronics PO Box 1040 Ottawa IL 61350 PH 815 433 5100 FAX 815 434 7094 Hexadecimal to Decimal Conversion Each Hex digit is the decimal equivalent value of the hexadecimal symbol Example Convert 10FC hexadecimal to decimal Decimal 1st Hex digit x 4096 2nd Hex digit x 256 8rd Hex digit x 16 4th Hex digit 1 x 4096 4096 0 x 256 0 15 X 16 240 12 X 1 12 4348 10FC hex eguals 4348 decimal 4348 decimal eguals 10FC hexadecimal Decimal to Hexadecimal Conversion Example Convert 4348 decimal to hexadecimal 4348 decimal eguals 10FC hex
9. CE TR El Checklist The following items should be in the shipping carton 1 RS 485 Distributed Smart Switch 2 Instruction Manual 3 1 3 1 2 floppy disk Contact the shippers immediately if any of the items above is missing or has damage 485DSS3298 Manual 1 B amp B Electronics PO Box 1040 Ottawa IL 61350 PH 815 433 5100 FAX 815 434 7094 Specifications Model 485DSS Size 4 8 L x 2 15 W x 0 9 H Power 11 to 16 Vdc 75mA RS 232 Connection DB 25 male DTE configured RS 485 Connection Terminal Blocks Communications 9600 baud no parity 8 data bits 1 stop bit Figure 2 Top View of Circuit Board 5 a D mbs a E EE us mu dio O ma b A TE A Freno a e LE pS eo gt D ra pi zgjuam ts Z O jm E o Eip SELDI D RO f TM t ea a wc c4 mam MOM MM UC cece MR 3 B x d OFFADDRESS ON ul R23 O 2 R13 oS ow we a Bog ns o an Sos MM T our gi 5 24 T 2 Poad a S osmu B SS x120cm o 4 p13 eN a O ERB a U6 012018 Ss gt 3 2 VDC TN i sy u2 rim Z R28 12 voc cy i inf E U2 3 _ M ee 9 181
10. D RS 422 TERMINATION cccccccccceceesessceceeeceesesseaeececeenerseee 7 POWER SUPPLY L iki sea ini ii sia i n T ORAON i sis sese a us a as ais a is Taa ss aaa 8 Figure 5 Simplified Functional Diagram 0 0 0 kaka 9 COMMUNICATION CONFIGURATION cccsesscecececeesesssceeeeeceesesssceseeecensaaees 9 DISTRIBUTED SMART SWITCH COMMANDG cccsesssseceeececsenseaeceeeceeeenees 9 The Command String ses sia ies ieee sida 10 ON COMMONER a OA 10 ORF COMMANG ii vat aaa a van eda eda Lad ds vee age nda ladda a ai 11 STATUS REQUEST Command coocccinncnnonncnnoninnnnnnnnnonnnnnnnnncnnn nono nccnns 11 SETTING THE 485DSS ADDRESS ccccssccccececeesensscecececeesesseaeececeenensees 14 Tablet Address Within dali 14 BINARY FITE TRANSFER conato es ea ass a aa k tea a e 15 CHAPTER 2 SOFTWARE ccccssssscssssscsssscssscsssssssscssssscencsecsersoee 16 DESCRIPTION ica 16 HARD DRIVE INSTALLATION ccocococccononcccnononocanononinanonocnnoncccnnnnaconananecinnno 16 RUNNING DEMONSTRATION PROGRAM cccccocnncccnononononncccnnnnnocnnananinanos 17 APPENDIX A ASCII CHARACTER CODES ovoccncccccnnscsimoncorionoooos A 1 APPENDIX B DECIMAL HEXADECIMAL CONVERSIONS B 1 Table 5 Hex Dec Conversions ccoconoccooonccononcnononnncnonnnnonnnnncnnnnanonanacccnnnnns B 1 485DSS3298 Manual Table of Contents i B amp B Electronics PO Box 1040 Ottawa IL 61350 PH 815 433 5100 FAX 815 434 7094 APPENDIX C CABLE CHARTS
11. Distributed Smart Switch Model 485DSS Document No 485DSS3298 This product Designed and Manufactured In Ottawa Illinois USA of domestic and imported parts by B amp B Electronics Mfg Co Inc 707 Dayton Road P O Box 1040 Ottawa IL 61350 PH 815 433 5100 FAX 815 434 7094 Internet http www bb elec com sales bb elec com support bb elec com 1998 B amp B Electronics August 1998 TABLE OF CONTENTS CHAPTER 1 HARDWARE ccccocnnocccnnnocononannconannoconnncononnonccncnocccnnococoss 1 INTRODUCTION EE E E S R E E S E E E T 1 Figure 1 Example of an RS 485 422 Multi Node Network 1 CHECK LEIS T sienai E i aaa ni i a i S an i aa S 1 SPECIFICATIONS dias 2 Figure 2 Top View of Circuit Board aaa aaa aaa kaka 2 PORT CONFIGURATION cccccesssssececececeessnccecececsesenseaececececssaeaeeeeeecenenaees 2 RS2485 422 POLE Ri aaa dida 2 Table 1 RS 422 485 Port cccccccccsssssssscsssecssscesssessesesssssessessesseseesesens 3 RS 232 POPE 5 B sasas sis sia tt asas 3 Table 2 RS 232 DTE DB25P Connector Chatt conoooococcncnonononnnnnononananos 4 RS 422 485 Witing aces coe seven Arias si o is A eaten ias I eats 4 2 Wire Mode A Ea si 4 Table 3 Component Values For Send Data Timing eee 5 Figure 3 RS 485 Wiring Diagram 00 aaa aaa aaa 6 AS WIT Mode ia ass abla ass das adden cas A a eats ids 6 Figure 4 RS 422 Wiring Diagram 00 eee eee eseeeeeseeecnereeeseeseeseeeeeees 7 RS 485 AN
12. If there is no need for termination place the jumper in the OUT position For more discussion of termination refer to B amp B Electronics free RS 422 485 Application Note Power Supply The 485DSS requires an unregulated DC power source that will supply 12 volts at 100 milliamps Connect the positive side of the power source to the 12VDC terminal block and the common side of the power source to the GND terminal block Refer to Figure 2 for the location of the terminal blocks and the polarity B amp B Electronics power supply Model 485PS2 is available for the 485DSS 485DSS3298 Manual 7 B amp B Electronics PO Box 1040 Ottawa IL 61350 PH 815 433 5100 FAX 815 434 7094 Operation The host computer of the RS 485 network controls each 485DSS on the network by sending them command messages These commands can turn a 485DSS on or off and can also request status from an individual or from all of the 485DSS s on the network The communication setup used to send and receive these commands are 9600 baud 8 data bits no parity and 1 stop bit Each command consists of four characters a start of message character two address characters and the command character All 485DSS s on the network will receive the command message strings sent by the Host but only the 485DSS with the matching address will execute the command Execution of the ON command raises the Request To Send RTS output line on pin 4 of the DB25 connector and
13. SS3298 Manual B amp B Electronics PO Box 1040 Ottawa IL 61350 PH 815 433 5100 FAX 815 434 7094 Running Demonstration Program Before you can run the demonstration program you must run the install program described in the Hard Drive Installation section above Make sure you have made the proper connections from the 485DSS to the RS 485 communication lines If you are running Windows exit Windows to DOS To run the program follow these steps from the DOS prompt QuickBasic Program 1 Type CD 485DSS and press the lt Enter gt key 2 Type DSS DEMO and press the lt Enter gt key C Demo Program 1 Type CD 485DSSI C and press the lt Enter gt key 2 Type DSS DEMO and press the lt Enter gt key Pascal Demo Program 1 Type CD 485DSS PASCAL and press the lt Enter gt key 2 Type DSS DEMO and press the lt Enter gt key 485DSS3298 Manual 17 B amp B Electronics PO Box 1040 Ottawa IL 61350 PH 815 433 5100 FAX 815 434 7094 Appendix A ASCII Character Codes DECIMAL to HEX to ASCII CONVERSION TABLE ASCII KEY DEC HEX ASCII DEC HEX ASCII DEC HEX ojo LO E w p S eS 2 3 4 5 6 7 8 9 A B Cc ni lt nja e Q r x pla Ro v ojo Oju 2 3 D CR M 4 E SO N 5 F SI O 6 0 m co ojo x o a ajo 31 F US ctrl 63 4
14. The LED labeled TD flashes when the RS 232 device is transmitting data The LED labeled RD flashes when data is being received by the 485DSS from the RS 485 network The LED labeled SEL turns on indicating that the RS 232 device has access to the RS 485 network Refer to Figure 2 Terminal blocks on the 485DSS connect the RS 485 signals and input power to the unit The RS 232 DTE signals of the 485DSS connect to a DB25 male connector An eight position switch located in the top center of the 485DSS sets the 485DSS s unique address Communication Configuration Before the HOST can communicate with a 485DSS the HOST must set its communication format to 9600 baud 8 data bits no parity and 1 stop bit After communicating with the 485DSS the HOST can reset its communication format to match the format of the RS 232 device attached to the 485DSS ALL data is passed through the unit after it has been selected The 485DSS does not have any buffering Distributed Smart Switch Commands The 485DSS constantly monitors the serial data received on the RS 485 422 port for a command string There are only three commands required to control the 485DSS the ON command the OFF command and the status request command 485DSS3298 Manual 9 B amp B Electronics PO Box 1040 Ottawa IL 61350 PH 815 433 5100 FAX 815 434 7094 The Command String All Command Strings consist of four ASCII characters The first character is the start of message
15. adecimal 4096 4348 4096 256 252 0 16 252 240 1 12 12 C 4th Hex digit 12 0 1 1 1st Hex digit ll o ll 0 2nd Hex digit ll al ll 1 3rd Hex digit B 2 Appendix B 485DS32985 Manual B amp B Electronics PO Box 1040 Ottawa IL 61350 PH 815 433 5100 FAX 815 434 7094 Appendix C Cable Charts These charts indicate some common cable wiring based on the 485DSS RS 232 and RS 485 422 ports Refer to the Port Configuration section of this manual for more information Chart 1 IBM PC DB25 Connector to 485DSS RS 232 DTE Port IBM PC 485DSS Serial Port Signal RS 232 DTE Port DB25 Connector Direction DB25 Connector Chart 2 IBM PC DB9 Connector to 485DSS RS 232 DTE Port IBM PC 485DSS Serial Port Signal RS 232 DTE Port DB9 Connector Direction DB25 Connector Chart 3 RS 232 DCE Device w DB25 Connector to 485DSS RS 232 DTE Port RS 232 DCE 485DSS Serial Port Signal RS 232 DTE Port DB25 Connector Direction DB25 Connector 3 485DSS3298 Manual Appendix C C 1 B amp B Electronics PO Box 1040 Ottawa IL 61350 PH 815 433 5100 FAX 815 434 7094 Chart 4 RS 232 DCE Device w DB9 Connector to 485DSS RS 232 DTE Port RS 232 DCE 485DSS Serial Port Signal RS 232 DTE Port DB9 Connector Direction DB25 Connector 2 3 3 2 5 lt gt 7 7 4 Chart 5 RS 422 485 4 Wire Device to 485DSS RS 422 485 Port RS 422 485 485DSS 4 W
16. ansmitting data to the Host the Send Data SD control circuit enables and disables the driver The 485DSS disables the driver when it is not transmitting data to the Host and listens to receives all communications on the network 4 485DSS3298 Manual B amp B Electronics PO Box 1040 Ottawa IL 61350 PH 815 433 5100 FAX 815 434 7094 SD control automatically enables the RS 485 driver by sensing the leading edge of the first character transmitted to the RS 232 port After transmitting the last character the send data timer circuit waits one character time 1 millisecond at 9600 baud before disabling the RS 485 driver There are two components in the timer circuit a resistor R15 and a capacitor C10 that make up the send data control circuit These components are factory selected for 9600 baud allowing the send data control to operate at 9600 baud or higher These two components disable the RS 485 driver approximately 1 millisecond after transmitting the last character To change to a baud rate lower than 9600 baud or to configure the send data control to match a specific baud rate of the RS 232 device remove R15 and insert the value specified in Table 3 into the R21 position Use Figure 2 to locate R15 and C10 NOTE The SD timing circuit does not control the RS 485 driver when the 485DSS sends reply messages to the host Table 3 Component Values For Send Data Timing Resistor Value Capacitor Value Baud Rate Time
17. ire Signal RS 485 422 Device Direction Terminal Blocks Chart 6 RS 485 2 Wire Device to 485DSS RS 485 422 Port RS 485 485DSS 2 Wire Signal RS 485 422 oy oreen EDI 7 Blocks O 8 C 2 Appendix C 485DS32985 Manual B amp B Electronics PO Box 1040 Ottawa IL 61350 PH 815 433 5100 FAX 815 434 7094 FEDERAL COMMUNICATIONS COMMISSION RADIO FREQUENCY INTERFACE STATEMENT Class A Equipment This equipment has been tested and found to comply with the limits for Class A digital device pursuant to Part 15 of the FCC Rules These limits are designed to provide reasonable protection against harmful interference when the equipment is operated ina commercial environment This equipment generates uses and can radiate radio frequency energy and if not installed and used in accordance with the instructions may cause harmful interference to radio communications Operation of this equipment in a residential area is likely to cause harmful interference in which case the user will be required to correct the interference at personal expense FCC Class A Equipment Statement
18. mal you might form a string like this DSSOAON CHR 19 0 A CHR 1 You could then send DSSOAON to select 485DSS address 10 0A hex Use similar strings for turning on the other 485DSS s OFF Command This command turns off all 485DSS s on the network and lowers the RTS output handshake line on pin 4 of the DB25 connector The command string consists of all non printable ASCII characters This command uses two broadcast characters DC2 decimal 18 in the address field Sending this command before sending a command that has a specific address address characters are printable keeps the RS 232 device from outputting any printable characters NOTE This command permits only the use of the broadcast characters in the address field Command character EOT decimal 4 Example 1 Turn off all the 485DSS s on the network HOST transmits Xoff DC2 DC2 EOT 19 18 18 4 decimal 13 12 12 4 hex The turn off string in BASIC might look like this DSSOFF CHR 19 CHR 18 CHR 18 CHR 4 You could then send DSSOFF to turn off all 485DSS s ALL data and control characters are passed through the 485DSS after it has been selected STATUS REQUEST Command The Status Request command requests the status of an individual 485DSS or the status of all 485DSS s on the network This command enables the Host computer to determine from each reply message received if the RS 232 device is requesting access to the network and if i
19. nding of the terms DCE and DTE The original design for connecting RS 232 devices together uses DB25 connectors and connects a DTE Data Terminal Equipment device to a DCE Data Communication Equipment device Each device will have inputs on pins that correspond to outputs on the same pins of the other device For example a DTE device transmits data out on pin 2 and a DCE device receives data in on pin 2 IBM PC s are DTE devices and modems are DCE devices Only TD and RD of the RS 232 port pass through to the RS 485 port when the 485DSS is ON The 485DSS raises and lowers the RTS output signal on the RS 232 port to reflect the connect state of the port This signal can notify the RS 232 device to start communicating to the Host or it can be an alarm output The Host can monitor the CTS input line to determine if the RS 232 device is requesting access to the network This input line could also be an alarm input NOTE If using RTS or CTS lines as alarms the user may have to design additional circuitry to properly interface to the alarm circuits Refer to cable charts in Appendix C for making your own cables 485DSS3298 Manual 3 B amp B Electronics PO Box 1040 Ottawa IL 61350 PH 815 433 5100 FAX 815 434 7094 Table 2 RS 232 DTE DB25P Connector Chart Signal Direction of RS 232 DTE Description Port 2 TD Transmit Data Output 3 RD Receive Data Input 4 RTS Request to Send Output 5 CTS Clear to Send
20. of message char Handshake input state Select State Least signf address character Most signf address character Start of message character When this command contains a specific address the 485DSS whose address matches the command address will wait for twenty milliseconds before transmitting the reply message If the command uses the broadcast characters to receive status from all 485DSS s on the network each 485DSS will delay transmitting its reply based on its address The amount of delay is equal to the unit s address in decimal multiplied by twenty milliseconds then add an additional 20 milliseconds 12 485DSS3298 Manual B amp B Electronics PO Box 1040 Ottawa IL 61350 PH 815 433 5100 FAX 815 434 7094 Example A unit with a decimal address of ten will have a delay of 220 milliseconds 10 x 0 02 0 02 0 22 seconds Command character ACK decimal 6 Example 1 To request status from the 485DSS set to address 11 OB hex decimal HOST transmits Xoff 0 B ACK 19 48 66 6 decimal 13 30 42 6 hex Reply A 0 B O 1 cr The reply indicates that the RS 232 port has no connection to the network on unit 11 and the CTS handshake line is in the high state Example 2 Request status from all the 485DSS s on the network HOST transmits Xoff DC2 DC2 ACK 19 18 18 6 decimal 13 12 12 6 hex Reply A 0 1 0 0 cr
21. t has access to the network By using this command the Host has the ability to prioritize all the 485DSS s on the network A specific address in the address field specifies a response from an individual 485DSS Placing broadcast characters 485DSS3298 Manual 11 B amp B Electronics PO Box 1040 Ottawa IL 61350 PH 815 433 5100 FAX 815 434 7094 in the address field specifies all 485DSS s on the network This command temporarily turns off disconnect the RS 232 port from the network while transmitting the reply message The reply message transmitted by the 485DSS consists of six ASCII characters The first character is the acknowledge character an upper case A decimal 65 The second and third characters represent the hexadecimal address of the 485DSS that sent the message The address range is from 0 to 255 HEX 00 to FF The fourth character indicates the select state of 485DSS a 0 decimal 48 indicates the RS 232 port does not have a connection not selected to the network and a 1 decimal 49 indicates the RS 232 port has a connection selected to the network The fifth character indicates the state of the CTS handshake input line on pin 5 of the RS 232 port connector A 0 decimal 48 indicates a low state on the CTS input pin and a 1 decimal 49 indicates a high state on the CTS input pin The sixth character is the end of message character a carriage return decimal 13 Reply Syntax A cr bo End
22. ta A simple solution to this problem is to change to a different baud rate before transferring binary files 485DSS3298 Manual 15 B amp B Electronics PO Box 1040 Ottawa IL 61350 PH 815 433 5100 FAX 815 434 7094 Chapter 2 SOFTWARE Description The Distributed Smart Switch Demonstration DSS_DEMO Program IBM PC or Compatible provides the user with examples of how to receive and transmit commands to the 485DSS The DSS_DEMO EXE is a DOS executable program written in QuickBasic that will send turn on turn off and status request commands to the 485DSS The program also monitors reply messages from any or all 256 addresses The source code is written in QuickBasic DSS DEMO BAS Borland Pascal DSS DEMO PAS and Borland and Microsoft C C DSS DEMO C The source code provides an illustration of how to send and receive commands for the 485DSS SimpCom Version 1 03 is required to recompile DSS_DEMO C and DSS_DEMO PAS This program is provided on one 3 1 2 720K diskette If a 5 1 4 diskette is required please contact B amp B Electronics NOTE This is a demonstration program only and not intended for system applications Hard Drive Installation To install on your hard drive follow these steps 1 Place the disk in drive A Go to a DOS prompt Type A and press the lt ENTER gt key Type INSTALL and press the lt ENTER gt key list of all files on the diskette is in the file FILES LST gt 0 ND 16 485D
23. u could then send DSSALLRS to request status from all the 485DSS s on the network Setting the 485DSS Address Assign each 485DSS on the RS 485 network its own unique address To set the address use the eight position DIP switch on the 485DSS labeled SW1 Refer to Figure 2 for the location of the switch To access this switch you will need to remove the top cover of the 485DSS Insert a small screwdriver in the slot in the side of the cover and twist to remove it Each switch position is equal to a specific weight value Set the 485DSS to any decimal address from 0 to 255 To assign the new address to the 485DSS cycle the power on the unit Table 4 Address Switch OFF Weight False ON Weight True Factory Default Address 0 14 485DSS3298 Manual B amp B Electronics PO Box 1040 Ottawa IL 61350 PH 815 433 5100 FAX 815 434 7094 Example 1 To set the address to decimal 21 15 hex you would turn on switches 1 3 and5 1 4 16 21 Example 2 To set the address to 123 decimal 7B hex turn on switches 1 2 4 5 6 and 7 1 2 8 16 32 64 123 NOTE It is important that the address you select is not already being used on the network Binary File Transfer When transmitting binary files through the Distributed Smart Switch it is possible that a string of characters could resemble a 485DSS command message If this would happen there could be a disruption in the transfer process and a loss of da
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