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1. Serial Communications Boards CYB 1422C Single Port PCMCIA RS 422 485 Serial Card USER S MANUAL REVISION 1 NOVEMBER 2000 1 11 7 99 No part of this manual may be reproduced without permission CyberResearch Inc www cyberresearch com 25 Business Park Drive Branford CT 06405 USA 203 483 8815 9am to 5pm EST FAX 203 483 9024 Copyright 2000 CyberResearch Inc All Rights Reserved The information in this document is subject to change without prior noticed in order to improve reliability design and function and does not represent a commitment on the part of CyberResearch Inc In no event will CyberResearch Inc be liable for direct indirect special incidental or consequential damages arising out of the use or inability to use the product or documentation even if advised of the possibility of such damages This document contains proprietary information protected by copyright All rights are reserved No part of this manual may be reproduced by any mechanical electronic or other means in any form without prior written permission of CyberResearch Inc TRADEMARKS CyberResearch and CYB 1422C are trademarks of CyberResearch Inc Other product names mentioned herein are used for identification purposes only and may be trademarks and or registered trademarks of their respective companies NOTICE CyberResearch Inc does not authorize any CyberResearch product for use in life support systems med2. Figure 4 2 RS 485 I Talker Many Listeners TXDF RXD n 1200 TXD A RXD n EU Tu RAS xn RXD1 RXD2 RXDn 2 RXDn 1 Note The Receiver end of MAIN line terminated in characteristic impedance by ONBOARD resistor networks stubs off the main not terminated In the above scheme one RS 485 device is talk only it transmits data but it does not receive any The other RS 485 devices are receive only they do not transmit any data at all 32 Figure 4 3 Half Duplex Wiring RXD xp gt TXD P TXD RS 485 Many Talkers Many Listeners Half Duplex Another popular RS 485 layout is for multiple talkers and multiple listeners This is shown in Figure 4 4 below This is also known as party line transmission It is imperative to have some method of preventing two devices trying to drive the data lines at the same time The normal method is to use the RTS line as a talk enable The RTS line should go true immediately prior to the data transmission and go false immediately after the last byte in the stream is sent See Figure 4 3 for jumper settings Figure 4 4 RS 485 Many Talkers amp Listeners Half Duplex gx qo Ek 4TXD n 120W Pg 120W TD Jj mdp CERXDI e RXDn RXD1 RXDn RXD2 RXD3 p RXDn 1 m RRDZ mt RXD3 i RXDn 1 TXD2 TXD3 TXDn 1 TXD2 TXD3 TXDn 1
3. Note BOTH ends of MAIN line terminated in characteristic impedance stubs off main line not impedance since both ends receive The twisted pair ends are wired to both RXD amp TXD and RXD amp TXD at each RS 485 device RS 485 Many Talkers Many Listeners Full Duplex The RS 485 many talkers many listeners Full Duplex system can be used when all the RS 485 devices have separate Transmit and Receive channels There is NO multiplexing of the TXD and RXD signals on the same device This system is especially useful when there is no flow control available on the PC usually due to the use of a third party communications program that prevents the use of the RTS signal as a transmit enable control via the TXD GATE jumper It can be used in the following situations a The PC is connected to only ONE RS 485 device b The PC is communicating with several RS 485 devices that are each able to recognize and respond to their own unique address The RS 485 devices only drive their TXD lines when they are responding to requests from the PC to send data In effect the RS 485 device s address and the command it receives is used to control access to the devices TXD channel This is a Full Duplex system Two twisted pair cables are required One twisted pair is the PC s TXD channel it carries the data sent from the PC s TXD outputs to the RXD inputs of each of the RS 485 devices The second twisted pair is the Devices TXD channel it carries the
4. data sent from each of the devices TXD outputs to the RXD inputs of the PC 33 The advantages of this system are great since no new communications software 1s needed and the PC can talk and listen at the same time In effect the handshaking is performed by the intelligence of the RS 485 devices attached to the PC When wired as in Figure 4 6 below the PC can transmit data at any time and all the RS 485 devices 1 to n simultaneously receives it Only one of the RS devices may talk 1 e transmit data at any one time Each RS485 device recognizes commands and data addressed to it it only talks when the PC commands it to do so When the RS485 device receives the command talk from the PC it gates its TXD drivers on sends the data down the device TXD channel and disables its TXD drivers The other RS485 devices remain in the receive only mode when they are not being addressed they do not transmit any data at all Figure 4 5 RS 485 Full Duplex Wiring TXD TXD RXD RXD RXD d p RXD TXD Figure 4 6 RS 485 Full Duplex PC s TXD CHANNEL PC Pin2 Devicein TXD RXD n 1200 TXD 4 q RXD n PC Pinl RXD1 RXDZ RXDn 1 RXDn 2 Device l Device 2 Device Device in 1 n 2 _ PC Pin7 Devices TXD CHANNEL nen Teen RXD 5 TXD n 1200 RXD TXD n PC Pin6 EXT TXD2 TXDn 1 TX
5. Dn 2 Device tl Device 2 Device Device n 1 n 2 Note The receiver end of MAIN line terminated in characteristic impedance stubs off the main not terminated 34 Optional Grounding Arrangements Proper operation of the cable circuit according to TIA EIA 485 A 1995 requires that the cable ground shield is not connected directly to the equipment ground shield A current limiting resistor should be used in series with the shield to avoid possible large current flow due to differences in ground potential Any one of the methods shown in Figure 4 7 below can do this Figure 4 7 Optional Grounding Arrangements For A PCI RS 422 485 Card Configuration A Configuration B SG GWG SG Signal Ground Interchange circuit GWG Green wire ground of power system Configuration A The circuit common of the equipment is connected to protective ground at one point only by a 100 Q 20 resistor with a power dissipation rating of 1 2W An additional provision may be made for the resistor to be bypassed with a strap to connect signal common and protective ground directly together when specific installation conditions necessitate Configuration B The circuit common shall be connected directly to protective ground The same configuration need not be used at both ends of an interconnection however care should be exercised to prevent establishment of ground loops carrying high currents Note Under certain ground conditions in configura
6. E 9729 etc see above RS 485 Gating amp Multiplex Jumpers as factory set RS 485 Operation The RS 485 standard is intended for up to 32 driver receiver pairs on the bus The line drivers used in the Serial Solutions RS 422 485 card are designed to work correctly in both RS 422 and RS 485 systems The main difference therefore is in how the system is implemented Though the card uses a 9 pin D connector in general not all the lines are used for RS 485 systems The RTS and CTS lines though driven by the card are usually not connected In two wire Half Duplex configurations the TXD line is connected to the RXD whilst the TXD line is connected to the RXD only one pair of twisted wire cable is used in RS 485 Half Duplex communications The hardware handshaking performed by the CTS and RTS lines in RS 422 systems are handled by a software protocol in RS 485 systems In situations where more than one device may transmit data on the shared data line each cards RTS line is used as a gating signal to enable the TXD driver only when that card needs to transmit data 1 e set TXD GATE or AUTO jumper This mechanism prevents bus contention caused by multiple transmitters holding the line in opposing states Revision 3 and higher versions of this card have a facility which automatically gates 31 the RTS line thus enabling the transmitter independently of any software This auto gating is described in more detail in the pre
7. ance These terminating impedances stop echoes caused by the serial data being reflected back at the cable ends It is not necessary to terminate the transmitter end of the twisted pair The AT Dual Port RS 422 485 Opto Isolated AT Dual Port RS 422 485 and AT Velocity RS 422 485 cards have the correct 120 Ohm nominal terminating resistors for the RXD twisted pair line and the CTS twisted pair line fitted on the RS 422 485 card for both the serial ports on the card There is no need to add any more at the PC end The terminating impedances shown later in the wiring diagrams of Figure 4 1 Figure 4 2 Figure 4 4 amp Figure 4 6 are automatically provided by the on board resistors and do not have to be added by the user Failsafe Open Circuit Detection Open circuit is when there are no drivers on the circuit This occurs by design in party line multi driver receiver systems and unintentionally when the twisted pair line is accidentally cut or disconnected or the transmitting device fails In RS 485 party line systems there are extended periods of time when none of the many possible talkers are gated onto the bus This is known as the line idle state and occurs when all the driver outputs are in the high impedance state The lines float perhaps being pulled to the high or low state by noise or other voltages on the line Without failsafe open circuit detection false start bits are detected by the receivers either corrupting good communication
8. ble in this window are Baud Rate Data Bits Parity Stop Bits Flow Control Change to suit remote device 14 Restore Defaults When clicked this will reset the selected port to the default values of Baud Rate 9600 Data Bits 8 Parity None Stop Bits 1 Flow Control Xon Xoff Maximum Baud Rate Setting These settings allow access to the faster data rates available on this card The faster rates are not enabled by default for compatibility purposes The faster data rates are only available directly from your application 1f it uses the standard Windows dialogue for serial port settings Baud Rate Multiplier This enables applications that do not use the standard Windows serial port configuration dialogue to access the faster data rates e g with this option enabled an application which selects 115 200 baud will actually set the hardware to the fastest possible rate of 921 600 baud In other words the baud rate is multiplied by a factor of 8 Click on the Serial Solutions tab PCMCIA R5422 PORT COM Properties Settings available in this window are 485 Mode This option enables the card to be switched into full or half duplex 2 or 4 wire mode Please note that the supplied cable requires modification for 2 way communication in half duplex mode 15 Windows 2000 Installation Insert the card into an available type2 socket This can be done even if the machine 1s powered If installing from a powe
9. e 3l RS 48 5 A le E E TT Aa ia ul T abet 32 RS 485 One Talker Many Listeners Half Duplex ceea eeeeeeee 32 RS 485 Many Talkers Many Listeners Half Duplex esee 33 RS 485 Many Talkers Many Listeners Full Duplex seeeeeeessess 33 Optional Grounding Arrangements e eee eee eee anna enne 35 CHAPTER 1 HARDWARE GUIDE Introduction This chapter details the specifications of the PCMCIA 1 Port RS 422 485 Serial card PCMCIA 1 Port RS 422 485 Card Features Reliable communications up to IKM 100 16C550 PC Compatible serial ports up to 1 Megabaud 16950 Compatible FIFO provides 128 byte input and 128 byte output buffer on each port Full modem control TX RX RTS CTS and GND signals Fully double buffered for reliable asynchronous operation High speed integrated circuitry ensures operation with fast PC s e g 650 MHz Pentium III Fully Plug and Play Dimensions 2 x 3 3 in 85x55 mm I O Connection Serial Port 9 pin Male D type Weight 16g Configuring PCMCIA Cards PCMCIA cards by definition require no hardware configuration and can be installed directly from the box CHAPTER 2 INSTALLING IN YOUR COMPUTER a This card is hot plug compatible it may be inserted into your PCMCIA type 2 slot when the machine is either off or powered on Please refer to your machine user guide for detailed instructions on inserting a PC card CHAPTER 3 SOFTWARE INSTALLATION Introducti
10. edure eceeeeeeeee nennen 8 Windows 98 Floppy Installation Procedure esee 10 PCMCIA Card Setup in Win 95 Win 98 and Win Millennium 12 PCMCIA Port Setup in Win 95 Win 98 and Win Millennium 13 Windows 2000 Installation sucer oor b obi pep on Oba conecte aud dal i vo et aeuo 16 Windows 2000 CD ROM Installation Procedure een 17 Windows 2000 Floppy Installation Procedure eeeeeeeeeee 20 PCMCIA Port Setup in Windows 2000 ranpa a earst 22 Windows NT4 Installation eeeeeeeeeeeeeeeeee eee eee eee eee eee eee aaa ennt etnnt naue 24 Windows CE InstallatiOlbucu on ero estat etate oboe weaned eee ees Beas e 26 CHAPTER 4 ADDITIONAL RS 422 485 OPERATION ee eee ee eee neenon o oou oue 29 Phe R S5 422 Standard sic sesh einer iri aa dela sed aan iau lac baia 29 TheR 5 455 SUDOAEQ aoreet dt casn a an ia acne bateti bobi taia 29 Terminabme In pedanCeS iscate i bataia DOR ll dolar E ete tu irita 30 Failsafe Open Circuit Detection du pe c ete dodo ana i oala tao atacati dc ad ia as 30 Fallsate Short Circuit PEOtGGUIOEB uoces ate oase datata ala ao caut al a lac aia 3 30 155 422 ODpetatlotia i ii PH a d e ia fr 530 darul 30 RS 422 Seral Port Cables ooo coat ive obe oboe niodo afar Drd nte oet aped aaa r 3 R5 465 OPE Oli ut tech tecum vn bow il sudes custos ousid
11. es Click Device Manager 22 Click on Ports COM amp LPT 4 Device Manager E E BRAIN HIFASS465 a Computer H E Disk drives EH Display adapters G28 DVDICD ROM drives Sy Floppy disk controllers H E Floppy disk drives H IDE ATA ATAPI controllers Ha Keyboards E Mice and other pointing devices Monitors E E Hulti port serial adapters XI Brain Boxes Limited 1 Port PCMCIA 422 485 Card PM 120 E H PCMCIA adapters E i Ports COM amp LPT Serial Part COM4 om y Communications Part COMI i WY Printer Port LPT1 B P Sound video and game controllers System devices E Universal Serial Bus controllers Double click on Serial Port COM4 Communications Port COM1 Properties Select the Port Settings tab Click on Advanced 23 From this screen COM port allocations can be changed Advanced Settings for COM1 COM1 COMA E COM COMS in use COMA in use PT Windows NT4 Installation Though the PCMCIA 1 Port RS 422 485 card can be used in Windows NT4 it is not yet available as a hot pluggable card Also not available is the half duplexing option Before inserting the card click on Start gt Settings gt Control Panel Wr Settings p E Control Panel ma u z e 2 24 E Control Panel gs 2 A Keyboard Modems Multimedia A Hetwork FL Card Printers PCMCIA Double click on the Ports icon COM Note the COM Ports li
12. ical equipment and or devices without the written approval of the President of CyberResearch Inc Life support devices and systems are devices or systems which are intended for surgical implantation into the body OR support sustain life and whose failure to perform can be reasonably expected to result in injury Other medical equipment includes devices used for monitoring data acquisition modification or notification purposes in relation to life support life sustaining or components required are not subject to the testing required and are not submitted to and diagnosis of humans Table Of Contents CHAPTER 1 HARDWARE GUIDE eeseoseessesssossossesseoseoseessesseoseossossesssossossesseoseossessesoe 1 TMIPO CUCU OM sega iza Ae noa ocean E au Dal z v la peer vale a ta l PCMCIA 1 Port RS 422 485 Card Features uox etes a eden aa 2 ata 0 orb Dat EE EE l Contieuring PEME IASC ards iesea aa 8 nn a palat ut l CHAPTER 2 INSTALLING IN YOUR COMPUTER ccccsccscccccccccccccccscceces 2 CHAPTER 3 SOFTWARE INSTALLATION seeseoseessesseossosseoseoseoseossesseoseossessesososeo 3 In O GUC Oeae EE T m 3 Windows 9S Inst lat Oins eiie n rii heeds Pe 3 Windows 95 CD ROM Installation Procedure eee eee ee eene 4 Windows 95 Floppy Disk Installation Procedure e eee eee eee eee 6 Windows 98 and Windows Millennium Installation een 7 Windows 98 CD ROM Installation Proc
13. les m Type a l then click OK Windows 98 and Windows Millennium Installation e Windows Millennium Installation follows the same procedure as Windows 98 Installation e Insert the card into an available type 2 socket This can be done even if the machine is powered ON e If installing from a power off condition Windows 98 should then load normally During the booting process Windows 98 will detect the card and briefly display a message box indicating the detection process Add New Hardware Wizard e Windows will then display the Update Device Driver Wizard requesting insert any disk which came with the card Insert the CD ROM installation disk or the floppy disk into an appropriate drive and click Next Windows 98 CD ROM Installation Procedure Choose the Search for the best driver for your device Add New Hardware Wizard Click Next Select Specify a location Add New Hardware Wizard drives Sdiskimgssswinds 7 lt B tees Type Drive MiskimgNswin9xM where Drive is the letter of your CD ROM Drive Click Next Add New Hardware Wizard Click Next Click Finish Windows 98 Floppy Installation Procedure Choose the Search for the best driver for your device Add New Hardware Wizard Click Next Add New Hardware Wizard Select Floppy disk drives Click Next 10 Add New Hardware Wizard Click Next Click Finish 11 PCMCIA Ca
14. o data will ever be transmitted when the receiver is unable to accept it due to a full input buffer etc And so no data will be lost RS 422 Serial Port Cables Use screened twisted pair Belden cable 9729 and 9829 L type 2493 and 2919 or IBM Part No 4716748 cable to make the RS 422 connection Unscreened Belden type 8795 may also be used in less noisy environments The on board resistor networks terminate the receiving end of the twisted pair cable in its characteristic impedance Figure 4 1 Serial Port I To Other PC Cable SERIAL PORT 1 Side Other PC SERIAL PORT Side 9 Pin Female D Connector 9 Pin Female D Connector SCHEMATIC REPRESENTATION 5 GND GND 5 n DY cuni a DD ane 0m MS pong m cow ACTUAL REPRESENTATION 5 GND TXD 1 m 9 CTS RXD 6 4 RTS TXD oe 8 CTS RXD4 7 3 RTS RTS 3 7 4 RXD CTS 8 2 TXD RTS 42 6 RXD CTS 9 1 TXD GND 5 E Note Receiver ends terminated in characteristic impedance ONBOARD resistor networks USE BELDEN TYP
15. on This section describes the software installation procedure allowing the PCMCIA 1 port RS 422 485 to be configured within the Windows 95 and Windows 98 Millennium operating systems Windows 95 Installation e Insert the card into an available type2 socket This can be done even if the machine is powered ON e If installing from a power off condition Windows 95 should then load normally During the booting process Windows 95 will detect the card and briefly display a message box indicating the detection process Update Device Driver Wizard e Windows will then display the Update Device Driver Wizard requesting insert any disk which came with the card Insert the CD ROM installation disk or the floppy disk into an appropriate drive and click Next Windows 95 CD ROM Installation Procedure Update Device Driver Wizard Click Other Locations Select Other Location dive diskimgssswins Lok camee Type lt drive gt diskimg sswin9x substituting the letter of your CD ROM drive for lt drive gt Click OK Update Device Driver Wizard Click Finish Insert Disk X Click OK Copying Files e drive diskimg sswind kd Type lt drive gt diskimg sswin9x substituting the letter of your CD ROM drive for drive Click OK Windows 95 Floppy Disk Installation Procedure Update Device Driver Wizard Click Finish Insert Disk X Click OK Copying Fi
16. r off condition Windows 2000 should then load normally During the booting process Windows 2000 will detect the card and briefly display a message box indicating the detection process Found New Hardware Wizard b Welcome to the Found New Hardware Wizard This wizard helps you install a device driver for a hardware device Ta continue click Nest Windows will then display the Found New Hardware Wizard requesting insert any disk which came with the card Insert the CD ROM installation disk or the floppy disk into an appropriate drive and click Next Found New Hardware Wizard Install Hardware Device Drivers A device driver is a software program that enables a hardware device to work with an operating system Select Search for a suitable driver for my device Click Next Windows 2000 CD ROM Installation Procedure Found New Hardware Wizard Locate Driver Files Where do you want Windows to search for driver Files n del peperere ue ie e vez Hd n za Select Specify a location Click Next 17 Found New Hardware Wizard 2 drive diskimgssswinzk Type lt Drive gt diskimg sswin2k where Drive is the letter of your CD ROM Drive Click OK Found New Hardware Wizard Driver Files Search Results The wizard has finished searching for driver files for your hardware device Click Next Please note at the time of creation of this document Windows 2000 i
17. rd Set up in Windows 95 Windows 98 and Windows Millennium Right click My Computer gt Properties on the desktop Properties Click on the Device Manager tab System Properties Floppy disk controllers Fy Hard disk controllers Fae Keyboard H Monitor Mouse E I Multi function adapters E Network adapters E H PCMCIA socket E kd Ports COM amp LPT NE Communications Part EO MT E PCMCIA R5422 PORT COM 0 ha W Printer Port LPT1 B m System devices EI 4 Universal serial bus controller Under Multi function adapters double click on PCMCIA 1 Port 422 Card 12 Click on the Serial Solutions tab DE ea mem The Serial Solutions tab allows modification of any user controlled features for the card PCMCIA Port Setup in Windows 95 Windows 98 and Windows Millennium Right click My Computer gt Properties on the desktop Properties 13 System Properties H Floppy disk controllers amp Hard disk controllers mam Keyboard H Monitor H A Mouse H Multifunction adapters on PCMCIA 1 Port RS422 Card 4 Network adapters H PCMCIA socket E E Ports COM amp LPT i Communications Port COM1 ME PCMCIA R5422 PORT COM2 0 9 Printer Port LPT1 H System devices zT Universal serial bus controller Under Ports COM amp LPT double click on PCMCIA RS422 PORT COM 1s the number allocated to the port Click on the Port Settings tab Settings availa
18. s or causing noise to masquerade as good data The on board fail safe open circuit detection causes the receiver to go to a known pre determined state and prevents false start bits and bad data being detected during open circuits Failsafe Short Circuit Protection Short circuits are when the two lines of a twisted pair are connected together This occurs due to either accidental damage to the cable or due to failure of one or more transmitter receivers on the line The short circuit condition is dangerous since damage to the receiver may occur and communication may be corrupted or prevented The on board failsafe short circuit detection prevents the line impedance from going to zero and thus protects the inputs of receivers and the outputs of drivers RS 422 Operation Generally in RS 422 systems all 8 signal lines from the 9 pin D connector participate in the data transfer sequence thus 4 twisted pair cables are used One twisted pair carries the TXD data outwards one pair brings the RXD data inward another pair carries the RTS handshake outwards and the fourth pair brings the CTS handshake inwards There is no need to carry the ground from one device to another This RS 422 arrangement allows data to be transmitted and received simultaneously since each signal has its own data cable pair In addition the receiver can set RTS true so telling the transmitter 30 on its CTS input that the receiver is ready to accept data In this way n
19. s still in BETA and it is not possible to get drivers signed by Microsoft 18 Digital Signature Not Found Click Yes Found New Hardware Wizard Completing the Found New Hardware Wizard MZ 1 Part PCMLIA 422 485 Windows has finished installing the software For this device The hardware you installed will not work until you restart your computer To close this wizard click Finish Pance Click Finish 19 Windows 2000 Floppy Installation Procedure Found New Hardware Wizard Locate Driver Files Where do vou want Windows to search for driver files eee zy brinza Select Floppy disk drives Click Next Found New Hardware Wizard Driver Files Search Results The wizard has finished searching Far driver files for your hardware device Click Next Please note at the time of creation of this document Windows 2000 is still in BETA and it is not possible to get drivers signed by Microsoft 20 Click Yes Click Finish Digital Signature Nat Found Found New Hardware Wizard Completing the Found New Hardware Wizard T 1 Port POMCIA 422 485 Windows has finished installing the software For this device The hardware you installed will not work until you restart your Computer Ta close this wizard click Finish Pais 21 PCMCIA Port Setup in Windows 2000 Right click My Computer gt Properties on the desktop Properties Select the Hardware tab System Properti
20. ssion Each signal is carried by a pair of wires and is thus a differential data transmission system Over distances up to 40 feet the maximum data rate is 10 Megabits per second and for distances up to 4000 feet the maximum data rate is 100 Kilobytes per second A 120 Ohm resistor should be used to terminate the receiving end of the line It is generally used between one transmitter receiver pair to only one other transmitter receiver pair but each output can drive up to 10 receivers RS 422 Standard 1 Driver up to 10 Receivers Line Length 40 Feet 12m 10 Mbits sec 400 Feet 122m 1 Mbits sec 4000 Feet 1219m 100 Kbits sec Li N N N A T T D R TT eR X The RS 485 Standard The RS 485 standard is similar to the RS 422 standard upon which it is based The main difference is that up to 32 transmitter receiver pairs may be present on the line at one time A 120 Ohm resistor should be used to terminate either end of the main line If more than one device may transmit data the RTS line is used as transmit enable signal so preventing contention between talkers RS 485 Standard Up to 32 Driver Receiver Pairs Line Length 40 Feet 12m 10 Mbits sec 400 Feet 122m Mbits sec 4000 Feet 1219m 100 Kbits sec uU y oP 20 Terminating Impedances RS 422 and RS 485 lines should be terminated at the end of the main branch of the RECEIVER in the cables characteristic imped
21. sted Click Cancel Power down your computer Insert the PCMCIA card then power up your computer Click on Start gt Settings gt Control Panel Ea Control Panel S i L4 E L m 25 Double Click on the Ports Icon ES Control Panel 2 Keyboard Modems 23 2 Network PC Card PCMCIA CUM 2 Multimedia a Printers The New port listed in this case COM2 will be the PCMCIA card port Windows CE Installation Place card in socket Select Start gt Programs gt Communications gt Remote Networking 26 Select Make New Connection with your pen a ofc a i a Tesco Met M uu rorem Armura We arra Drepp besoo via mr Wn porte porti Ten Net PL Type a name for the connection in the field under Type a name for the connection a IN Select Dial up Connection radio button Select Next 1Port_RS232Card tesco via mr modern The Dialog shows a modem icon with the name from the previous screen There is a drop down dialog underneath Select a Modem Select 1Port_RS422 485 Card 21 Select Configure button E a In Device Properties set the following Baud Rate 9600 Data Bits 8 Parity None Stop Bits 1 Flow Control None 28 CHAPTER 4 ADDITIONAL RS 422 485 OPERATION The RS 422 Standard The RS 422 standard defines a serial communications standard RS 422 is a high speed and or long distance data transmi
22. tion A above high ground currents may cause the resistor to fail therefore a provision should be made for inspection and replacement of the resistor 35
23. vious 485 half duplex section The three wiring schemes given described below are RS 485 One Talker Many Listeners HALF DUPLEX RS 485 Many Talkers Many Listeners HALF DUPLEX RS 485 Many Talkers Many Listeners FULL DUPLEX RS 485 Cable For best noise immunity use twisted pair cables to make the RS 485 connection In Half Duplex wiring only twisted cable pair is needed Two twisted pair cables are needed for Full Duplex communications Use screened twisted pair Belden cable 9729 and 9829 UL type 2493 and 2919 or IBM Part No 4716748 cable to make the RS 485 connection Terminate the twisted pair cable at either end in its characteristic impedance which for the Belden 9729 cable is 120 Ohms Unscreened Belden type 8795 may also be used in less noisy environments RS 485 One Talker Many Listeners Half Duplex There are several schemes for connecting RS485 devices depending on the characteristics of the system In many cases there will be only one device which can transmit data and all the others simply listen to it This scheme is used for theatrical lighting intensity control in the DMX512 standard This is shown in Figure 4 2 below For the talker the RS 485 TXD GATE jumper should remain in the factory set position 1 e transmitter is always enabled There is NO multiplexing of the TXD and RXD lines Data is only flowing one way from PC outwards and is thus a Half Duplex configuration only one twisted pair cable is needed
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