6008-2.4, Allen-Bradley I/O Scanner Module For IBM® Personal
Contents
1. s dual port RAM contains output data that is sent to the adapter The scanner sends out to the adapter a single 16 bit word of output data for each I O group in the I O rack Scanner V O Adapter Application Program Output Image 2 Asin gle word of Output Data Table for each I O group 18099 2 The I O adapter replies to the scanner with a single word of input data for each I O group in the I O rack The scanner puts the data into its input image table Along with the input data there is a block transfer status bit that tells the scanner whether a module in the I O rack is ready to do a block transfer Scanner l O Adapter E Asingle word of Input Data from Application each I O group plus status Program Table Input Quim Image H 18100 3 4 Application Program Chapter 3 PC I O Operation 3 The scanner checks the block transfer status bit to determine whether a block transfer should happen Only one block transfer is allowed per rack per I O scan If the bit is set the scanner performs the block transfer Scanner l O Adapter Block Transfer Write c S Block Transfer Read _ Dual port RAM up to 64 words 18101 Determining I O Scan Time For each I O rack the nominal single transfer time the time it takes to update2. Chapter 2 Remote I O Subsystem Figure 2 2 Two Slot I O Group a 16 bit input module and a 16 bit output module and its Corresponding Output Word and Input Word UO Group F DA Typical 1771 I O Module H L aT Input Output Terminals N amp j Terminals LII SI 0 CIT ay 0 o S ug 1 3 BM B 3 Tbe Se 4 UO Module Ea a a ae terminals use the octal 6 al S 6 numbering system 7 ESI ia 7 10 KSI sl 10 T HS II DS 11 jr E RS zx 13 mb ce 13 14 ISi a 14 2 SR 3 T i S 17 I i 4 p La ey U Output Word l l Each bit represents one terminal point l l shula hefu ho 9 8 7 6 5 BB i l l l Input Word l Each bit represents one terminal point b l tes 1312 11 10 9 8 716 slafsleli o 14658 Chapter 2 Remote I O Subsystem 2 4 Figure 2 3 shows how you assign each I O adapter an I O rack number 0 to 7 by setting switches on the adapter An I O rack is an I O addressing unit containing a maximum of 8 I O groups Figure 2 3 Typical 1771 I O Chassis with I O Modules Installed Showing the I O Image and Correspondin
3. Figure 3 2 Interrupt Service Routine Interfacing to Dual Port RAM Application Host Software Scanner s rogram 39 interrupt service routine amp 3 Dual Port C RAM Because the interrupt handler takes care of all details of the dual port RAM you needn t be concerned with the bits and bytes You should know however that the dual port RAM contains two areas of information The I O image tables which are comprised of an output image table and an input image table Each time control of the dual port RAM is transferred the interrupt routine copies new inputs from the dual port RAM to your program s data area and new outputs from your program s data area to the dual port RAM An area in which the host CPU sends commands to the scanner and the scanner returns confirmation and data Chapter 3 PC I O Operation Data Paths Input data follows this path An external switching device closes a digital input circuit in an input module When next asked by the adapter the input module reports the new input state The adapter updates its internal input image table by setting the bit corresponding to the particular input At the next scan the adapter reports the new input state to the scanner The PC I O Scanner updates the input image table in the dual port RAM by setting the bit that corresponds to the particular input The host interrupt handler reads the input image information
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5. VO Link Chapter 2 Remote I O Subsystem The Allen Bradley PC I O Scanner has a single port for an I O link You can connect up to 16 1771 I O chassis or adapter devices to the scanner on the remote I O link as shown in figure 2 1 The chassis are daisy chained along a shielded two conductor twisted pair cable up to 10 000 feet in length This remote I O link lets you locate I O modules close to monitoring and control devices of your system I O chassis are available in six sizes to hold up to 1 2 4 8 12 or 16 I O modules Figure 2 1 A PC I O Scanner Interfacing to an I O Subsystem IBM PC Hardware PC I O Scanner Card OSes aa osa ee 1771 ASB Adapter PLC 5 Processor in adapter mode UO Chassis UO Chassis PanelView E Hi e S E 1771 VO Modules 1771 UO Modules Up to 13 more I O Chassis 18098 Each 1771 I O module can contain up to 32 inputs or outputs which you connect to devices on your machine or process When an application requires only a few I O use our single point I O modules 2 1 Chapter 2 Remote I O Subsystem Remote I O Addressing 2 2 The PC I O Scanner s addressing capability allows you to configure the I O chassis for a maximum of 8 I O racks Each I O rack can have a maximum of 8 I O groups Each I O group can have a maximum of 16 inputs outputs The I O subsystem
6. a single I O rack is 7ms at 115 2k bits s or 10ms at 57 6k bits s Each block transfer takes 5ms plus 0 2ms per word at 115 2k bits s or 0 3ms per word at 57 6k bits s The total I O scan time is the sum of the individual times Example Consider an I O subsystem set for 57 6k bits s with 4 I O racks and a block transfer module in each I O rack For this example each block transfer module requires a block of 25 words The total I O scan time is 4 x 10ms 40ms 4 x 5ms 20ms 4x25x0 3ms 30ms approximate I O scan time 90ms 3 5 Chapter 3 PC I O Operation How the Host Accesses Remote I O Data Memory 3 6 Remote I O data is always available to the host CPU once the scanner is running I O data resides in the scanner s dual port RAM The scanner s dual port RAM has 6K bytes The host CPU and scanner exchange control of this area by means of interrupts When the scanner interrupts the host CPU the scanner is turning over control of the dual port RAM to the host When the host CPU interrupts the scanner the host either has the dual port RAM and wants to return it or the host doesn t have the dual port RAM but wants access to it For the host CPU we supply an interrupt handler or interrupt service routine that is automatically invoked when the scanner interrupts the host The interrupt service routine copies information as needed between your program s data area and the dual port RAM as shown in figure 3 2
7. can be configured for a maximum of 1 024 inputs and or outputs Each I O chassis contains either an I O adapter module or a programmable controller with which the PC I O Scanner communicates The I O adapter transfers I O data to and from its I O modules across the chassis backplane The programmable controller monitors and controls its I O across the 1771 chassis backplane as a real time distributed logic processor It transfers data to and from the scanner according to commands issued by the scanner Your application program addresses I O data in the scanner s dual port RAM based on the location on the link of the corresponding I O module This is defined during installation by s UO rack 0 7 s I O group 0 7 within the I O rack For discrete digital and analog I O modules the link location address of an individual input or output not only identifies the rack and group but also the input or output within the I O group An I O group corresponds to a 16 bit word in the input image table and a 16 bit word in the output image table as shown in figure 2 2 By setting switches at each chassis you select its addressing mode based on the density of the I O modules you are using If you select Then you have With two slot addressing two I O module slots per I O group 8 input output bits per slot one slot addressing each I O module slot as an I O group 16 input output bits per slot half slot addressing 32 input output bits per slot
8. cannot have two IBM PC I O Scanners operating in the same host The host software supports only single scanner systems Software Interrupt The host receives interrupts from the scanner by default through line IRQ3 which corresponds to software interrupt number OBh Results are unpredictable if you have any other software that uses that interrupt The scanner driver routines also use the timer follow on interrupt number 1 Ch If the host CPU has resident software that uses that timer interrupt execution of that software will be suspended while the scanner program is running and will probably resume if the scanner program executes the stop 6008 function Print spoolers are the most common class of programs to use the timer follow on interrupt The scanner doesn t use any host I O ports In relation to the host CPU the scanner runs asynchronously When either wants to get the other s attention it issues a hardware interrupt The host CPU and the scanner can postpone servicing an interrupt if it is already processing another interrupt task Scan List User Application b Application I O Scanner I O Image Tables Image Tables l Interrupt Service Routine Chapter 3 PC I O Operation The scanner maintains a scan list of adapters to be serviced by the scanner An adapter may appear once several times or not at all in the scan list The list starts simply with a list of adapters each occurring once but yo
9. file is copied to the area that contains other include files used with your compiler Run time Libraries The run time libraries are copied into their own library directories One directory for each memory model Library routines allow I O control and the issuing of commands setbit setbit setbyte clrbit setword putbyte putbit putword MR WAIT is a function contained in the library that is used to issue management commands 4 1 Chapter 4 Application Development 4 2 Commands for Configuring the Scanner There are two types of scanner commands block transfers and management requests Block transfers are s BLOCK TRANSFER READ s BLOCK TRANSFER WRITE Management requests are SET MODE AUTOCONFIGURE s SCAN LIST s LINK STATUS 1 SETUP s FAULT DEPENDENT GROUP A management request affects the operation of the scanner The following table summarizes the function of each management request Command Description SET MODE changes the scanner s operating mode to program test or run AUTOCONFIGURE goes on the link to see what devices are attached SCAN LIST changes the order in which adapters are scanned and their relative frequency LINK STATUS asks the scanner to report all information it has about the adapters that are connected SETUP changes the data transmission rate and connects or disconnects the line termination resistor FAULT DEPENDENT GROUP designates one or more groups of adapters in such
10. for 90 years A ROCKWELL INTERNATIONAL COMPANY A B designs manufactures and supports a broad range of control and automation products worldwide They include logic processors power and motion control devices man machine interfaces and sensors Allen Bradley is a subsidiary of Rockwell International one of the world s leading technology companies A With major offices worldwide 7 L A Algeria e Argentina e Australia e Austria e Bahrain e Belgium e Brazil e Bulgaria e Canada e Chile e China PRC s Colombia Costa Rica e Croatia e Cyprus e Czech Republic e Denmark e Ecuador s Egypt e El Salvador e Finland e France e Germany e Greece e Guatemala e Honduras s Hong Kong s Hungary e Iceland e India e Indonesia e Israel e Italy e Jamaica e Japan e Jordan e Korea e Kuwait e Lebanon e Malaysia e Mexico e New Zealand e Norway e Oman e Pakistan e Peru e Philippines e Poland lt Portugal e Puerto Rico s Qatar e Romania e Russia CIS e Saudi Arabia e Singapore e Slovakia e Slovenia e South Africa Republic e Spain e Switzerland e Taiwan e Thailand e The Netherlands e Turkey United Arab Emirates e United Kingdom e United States e Uruguay s Venezuela e Yugoslavia World Headquarters Allen Bradley 1201 South Second Street Milwaukee WI 53204 USA Tel 1 414 382 2000 Fax 1 414 382 4444 Publication 6008 2 4 October 1990 PN 955108 45 Supersedes 6008 2 4 July 1987 Copyright 1991 Allen Bradley Company
11. other third party board addresses otherwise you ll overwrite the memory areas of the third party boards Plugging in the Card The scanner card requires two adjacent slots in the host s backplane although there is just one row of connectors but you can use any full length two slot area you choose Install the card with mounting screws to maintain proper seating The scanner has a 15 pin male connector that is accessible through the back or side of the host computer The remote I O cable terminates in a 15 pin female D shell connector which is supplied A 3 Appendix B Specifications PC Minimum PCbus Hardware Configuration a standard AT or XT bus configuration PCbus Interrupts Select one of four levels 3 5 10 12 Scanner Configuration Place only one scanner per PC in your computer system Memory Requirement 6K bytes of RAM within the system memory area Environmental Conditions Operating temperature 0 to 60 C 32 to 140 F Storage temperature 40 to 85 C 40 to 185 F Relative humidity 5 to 95 noncondensing Compatibility Operating System DOS version 2 11 or higher Software Libraries Microsoft C compatible Lattice C Compatible Media Both 5 25 and 3 5 720K provided Disk Space Usage 100k Source Code Contact your local Allen Bradley Sales Office to order cat no 6008 SIDC Contact your local Allen Bradley Sales Office for third party software B 1 Appendix B
12. the remote I O link Through an adapter the PC I O Scanner can communicate with a wide variety of Allen Bradley I O modules to access digital inputs outputs analog inputs outputs motion control process controllers PID loop controllers operator interface distributed Programmable Controllers machine vision processors special function modules Figure 1 1 PC I O Scanner ELENEI 1 1 1 Chapter 1 PC I O Scanner Overview Benefits Easy to install A single twisted pair cable for I O communications can replace bundles of I O ribbon cables A single interface board can replace multiple I O boards Host software support The scanner comes with software libraries that are linked to your application program The libraries allow faster program development through the use of functions specific to Allen Bradley I O Enhances system I O performance The PC I O Scanner has its own communication processor thereby offloading the main CPU from I O tasks Compatible with a wide variety of Allen Bradley I O products The PC I O Scanner communicates across the Allen Bradley universal I O link to multiple adapters see Specifications Third party software availability Third party software is available for the PC I O Scanner This allows you to program the scanner with easy to use graphics and menus thus eliminating the need to know the C programming language How the I O Subsystem Meets Your Application Needs Remote
13. ALLEN BRADLEY Allen Bradley UO Scanner Module For IBM Personal Computers Car Ia GOD8 S1 Product Data EORR nli Important User Information Because of the variety of uses for this product and because of the differences between solid state products and electromechanical products those responsible for applying and using this product must satisfy themselves as to the acceptability of each application and use of this product For more information refer to publication SGI 1 1 Safety Guidelines For The Application Installation and Maintenance of Solid State Control The illustrations charts and layout examples shown in this manual are intended solely to illustrate the text of this manual Because of the many variables and requirements associated with any particular installation Allen Bradley Company cannot assume responsibility or liability for actual use based upon the illustrative uses and applications No patent liability is assumed by Allen Bradley Company with respect to use of information circuits equipment or software described in this text Reproduction of the contents of this manual in whole or in part without written permission of the Allen Bradley Company is prohibited 1990 Allen Bradley Company Inc PLC is a registered trademark of Allen Bradley Company Inc RediPANEL PanelView and CVIM are trademarks of Allen Bradley Company Inc IBM is a registered trademark of International Business Machin
14. Specifications Remote I O B 2 Maximum I O Configuration I O Link Cable Length amp Data Transmission Rate I O Scan Single Transfer Time I O Scan Block Transfer Time Adapter Devices Available 1 024 discrete inputs 1 024 discrete outputs 16 physical I O adapter devices 5 000 cable feet 115 2k bits s 10 000 cable feet 57 6k bits s 7ms rack nominal 115 2k bits s 10ms rack nominal 57 6k bits s Block transfer overhead 5ms for either rate Time per word 0 2ms 115 2k bits s 0 3ms 57 6k bits s Remote I O Adapter Module cat no 1771 ASB Single Point I O Adapter Assembly cat no 1771 JAB PLC 5 Processor Module in adapter mode cat no 1785 LT LT2 LT3 PLC 5 250 Remote Scanner I O link port in adapter mode cat no 51 50 RS2 Direct Communication Module cat no 1771 DCM PLC Interface Module cat no 3500 NA1 for digital AC and DC drives 1352 and 3450 Remote I O Adapter cat no 1336 MOD G2 for adjustable frequency drives 1336 Serial Port Connector cat no MOD S1 RediPANEL TM Pushbutton and Keypad Modules bulletin 2705 PanelView bulletin 2711 Option Module cat no 1 784 F30D for the T30 Plant Floor Terminal cat no 1 784 T30A T30C T30G 8600 CNC with remote I O adapter option cat no 8600 2085K CVIM TM set for adapter mode cat no 5370 CVIM ALLEN BRADLEY Allen Bradley has been helping its customers improve productivity and quality
15. a way that if one adapter in a group is faulted the scanner will instruct the others to be faulted too Code Example User Diagnostic Program Chapter 4 Application Development The manual IBM PC I O Scanner Module User s Manual publication 6008 6 5 3 contains many code examples identifying the different functions provided in the software libraries supplied with the scanner Figure 4 1 shows the start of a sample program with a call to setup_6008 and associated checks for error Figure 4 1 Code Fragment Programmed in C include lt stdio h gt include lt h_6008si h gt void main QMR pkt int status status setup 6008 1 1 1 0xC400 amp pkt if status OK printf setup failed commande s status s n xlat cmd status xlat conf pkt qmr stat if status C AUTOCONF amp amp status C SETUP printf scanner fatal error dMn fatal 6008 abort else mr_print stdout C AUTOCONF amp pkt You must know how to start a program under DOS to run the scanner s diagnostic program You can run the diagnostic program even if the I O cable is not attached We provide the source files of the diagnostic program on either a 5 25 or 3 5 diskette so that you ll have extended examples of successful programming for the scanner You should feel free to experiment by modifying them although we cannot support any modified program versions We also include an executabl
16. dog If the host computer doesn t respond within 100ms to an interrupt from the scanner the scanner assumes that the host program is no longer active In this case the scanner goes off the link and 50ms later the adapters set the output modules in last state or off according to your switch settings The scanner then goes into its power up sequence waiting for new start up commands from the host CPU Chapter 3 PC I O Operation The scanner watchdog feature lets you end one program run and start another without cycling host power Even if your program locks the host computer if you are able to do a soft reset Ctrl Atl Del the scanner will be ready for your program More importantly if your program fails or is interrupted even by a reboot of the computer all discrete digital outputs will be in last state or off according to the switches you set on the adapters 3 11 Host Software Chapter 4 Application Development You will need the MS DOS or PC DOS operating system version 2 11 or higher If you are using the Microsoft C version of the scanner driver software you ll need a Microsoft C compiler version 4 0 or higher With the Lattice C version of our software you ll need a Lattice C compiler and linker preferably version 3 10 or higher Here is a list of the host software H 6008SI H include file 6008SI LIB run time libraries U DI EXE user diagnostic program in executable form The include
17. e version of the diagnostic program so you can turn on the scanner Please note that all of the files on disks are copyrights of Allen Bradley Company Inc and may not be distributed or copied without our permission other than from the distribution disk to your hard disk or working disk 4 3 Chapter 4 Application Development Diagnostic Source Code Example 4 4 The remaining files whose names begin with U_ make up the source code for the user diagnostic program The files provide examples of how to control and how to get information from the scanner The executable form of these files U D1 EXE is a useful tool in testing the operation of the scanner interactively through the keyboard The U D1 program can initiate every possible command the scanner can do It should be the first program that is run after the scanner is installed in your PC U Dl C main program U DI H include file for the U_ C files U BT C single block transfer U BTC C continuous block transfers U BTM C multiple block transfers U DISC C full screen discrete I O U GET C keyboard handler U GROUP C single group discrete I O U_MR C management requests U PICK C main menu Appendix A Scanner Installation You ll complete these main steps to install a scanner module in the host CPU set the card s switch block for the memory address you selected earlier choose the interrupt request line the board will use with a jumper plug the scanner
18. es Corporation PC DOS is a trademark of International Business Machines Corporation Lattice is a registered trademark of Lattice Inc Table of Contents PC I O Scanner Overview ss e x x x x e e K K x x x x e 1 1 The Scanners Role 00 0 c cece eee eee neces 1 1 BEflelils ceux d or acte arae e pod d ders ERE RU ck eRe ae 1 2 Remote I O Subsystem sx x x x K K e e x x x x K Kee 2 1 How the I O Subsystem Meets Your Application Needs 2 1 Remote I O Addressing 0 cece eee eens 2 2 Distributed Processing of I O 00 00 cece cece 2 5 PC I O Scanner Operation LL 3 1 Main Components lusseeeseenennnne 3 1 Link Operation L 3 3 How the Host Accesses Remote I O Data 3 6 How the PC I O Scanner Operates 0 00 eevee 3 8 Application Development sss x x x x e e x x x x x e K x 4 1 Host Software ice ty exa Sooo aaah a Dade BY SERRE SS 4 1 Code Example 05 3 etx wv eead ed OPE K RR UE CERES 4 3 User Diagnostic Program 02 0 cece ees 4 3 Scanner Installation ss e e x x x x cece eee ee A 1 Specilicalionis sc xes 8 9 natae T RR Ra aec B 1 The Scanner s Role Chapter 1 PC I O Scanner Overview A scanner is a communication interface module that plugs into a host computer system The PC I O Scanner allows an IBM personal computer PC direct access to Allen Bradley universal I O products via
19. g Hardware for One Assigned Rack Number Using Two Slot Addressing I O Rack 8 O Groups Output Image Table Word in scanner s dual port RAM 0 1 2 5 ppc nb 6 7 Output Output Output Output Output Output Output lO Group This diagram shows a chassis assigned as one I O rack using 2 slot addressing Input Image Table Word in scanner s dual port RAM NOOB OM 17949 Distributed Processing of 1 0 Chapter 2 Remote I O Subsystem Up to this point we have discussed only direct control of I O Through a 1771 ASB or 1771 JAB adapter the PC I O Scanner directly monitors the status of input terminals and controls the status of output terminals The scanner also sends output status to and receives input status from a 1785 PLC 5 controller configured for the adapter mode or to a Direct Communication Module 1771 DCM in an I O chassis controlled by a PLC controller To the scanner the controller appears to be similar to an I O chassis with a 1771 ASB adapter However the controller s application program controls the status of its output terminals and controls the status of the input data to the scanner While outputs are controlled by the controller in this type of configuration the scanner provides supervisory control and monitoring The program in the controller could however use output data from the scanner to directly control some ou
20. in the dual port RAM and copies it to a duplicate input image table that is available to your program Your program now knows that an input on a particular input module is ON The path of output data is essentially the reverse of the input path Your program sets a bit in its output image table The program knows that this bit maps to an output on a particular output module The scanner interrupts the host The interrupt handler copies your program s output image for that rack to the dual port RAM At the next scan of the adapter that controls that particular module the scanner tells the adapter to update its output image table with the new state of the output The adapter tells the discrete output module the new output state The output module closes the digital output circuit Any external device attached to the output is activated Hardware Interrupt On the system board the scanner uses one of four interrupt lines as shown in figure 3 3 The interrupt line is selected with a jumper on the scanner board The choices for the interrupt lines are 3 5 10 12 3 7 Chapter 3 PC I O Operation How the PC I O Scanner Operates 3 8 Figure 3 3 Four Interrupt Lines on the PC I O Scanner Note Interrupt line designations are not actually shown on the board OON ULU 9 pole OOo Default setting Choose an interrupt line that does not conflict with any other boards in your system You
21. into the expansion slots in the host connect the I O cable to the scanner The scanner card has one block of ten switches to be set at installation time as shown in figure A 1 For a complete listing of switch settings refer to the IBM PC I O Scanner Module User s Manual publication 6008 6 5 3 Appendix A Scanner Installation Figure A 1 PC I O Scanner Showing Switch Settings TRENT ll NM HERD T i 5s m R ea ae Switches on Close 6 4 5 i2 3 off Open Es Switches 7 10 for 8 bit or 16 bit data bus Set switches 1 6 for RAM address RAM Address Figure A 1 shows switches 1 thru 6 set for memory address CO000h for an IBM PC AT or another machine with a 16 bit bus If you re running on a PC XT or another 8 bit bus machine or if you want to configure the scanner at an address other than C0000h you must change the switches These switches let you configure it to any starting address in RAM from 04000h to FCO000h in increments of 4000h 16Kbytes The scanner cannot be configured to operate in extended or expanded memory The scanner card will occupy 1801h 6K 1 bytes beginning at the address you select You must select an address that starts a free 6K 1 byte range Appendix A Scanner Installation Avoid selecting a RAM address range that conflicts with
22. k Operation Chapter 3 PC I O Operation No direct communication exists between the host CPU and the I O rather the host CPU communicates with the I O image table of the scanner s dual port RAM Input status is read from the input image table and outputs are written to the output image table of the scanner s dual port RAM Data Transfer Methods Data transfer is the movement of data to or from I O modules There are two types of data transfers Single transfer is the exchange of a single unit of data 8 16 or 32 bits to or from each I O module in an I O chassis A single transfer occurs during each scan of an I O adapter a Block transfer is the exchange of up to 64 words in a particular direction between a scanner and an I O module The scanner initiates a block transfer as a one time event Asynchronous Scanning The data transfers from the host CPU are asynchronous to the PC I O Scanner s remote I O update Asynchronous means that the scanner continually reads from and writes to each I O adapter independently of your application program Scanning an Adapter The scanner master polls each adapter slave on the I O link in a circular scan list which means that each time the scanner reaches the end of a list it starts again at the beginning as shown in figure 3 3 To scan an adapter at least two and possibly three events occur 3 3 Chapter 3 PC I O Operation 1 The output image table in the scanner
23. n list at the point of the adapter most recently scanned If the scanner works its way through the scan list to the same point without receiving an interrupt from the host CPU the scanner will interrupt the host If the scan list contains no adapters the scanner will wait for 5ms before interrupting the host CPU Thus the I O image tables are refreshed once per scan Partial refreshing takes place more frequently if your program executes a lot of block transfers or management requests Whenever the dual port RAM is transferred the I O image tables are refreshed to the point of the scanner s advance in the list since the last interrupt Host Watchdog In the event of a program crash or your program gets into an infinite loop there is no way for the interrupt service routine ISR to recognize all failures But there is a host watchdog scheme Essentially your program must take a particular action every so often by default every second If the ISR recognizes that the required action has not been taken recently enough the ISR infers that your program has failed and stops talking to the scanner The scanner recognizes that quiet as a host failure and goes off the link within 50ms All the adapters go inactive and output terminals go to either their last state or off as determined by switches you set on the adapters Details of this feature are in the IBM PC I O Scanner Module User s Manual publication 6008 6 5 3 Scanner Watch
24. tputs and send some input status 2 5 Main Components Chapter 3 PC I O Scanner Operation Figure 3 1 shows the main components of a typical system host CPU an IBM PC computer system that runs the application program and drives the scanner PC UO Scanner PC I O Scanner cat no 6008 S1 physically resides in the host computer system The scanner is a full length double width card and occupies two standard XT or AT slots The Allen Bradley I O Scanner Module lets you connect an IBM personal computer PC to an Allen Bradley 1771 I O subsystem PCbus the circuit board or backplane that the scanner plugs into T O adapter the device on the I O link that communicates to the scanner Up to 16 adapters can connect to one scanner remote I O cable a twinaxial shielded two conductor twisted pair cable that connects the scanner card to each adapter in the I O subsystem Allen Bradley recommends Belden 9463 cable 3 1 Chapter 3 PC I O Operation Figure 3 1 Scanner s Main Components IBM PC Hardware T 1 l UO Input Output Chassis ud Modules Host Processor PC I O Scanner a 1771 VO IBM PC Bus Adapter Motor Starter Le J cn Switch 1771VO Input Output Chassis Modules Modules Remote pee nae orn VO Link PLC 5 Family Processor in adapter mode Operator Interface Terminal Up to 13 more V O Adapters 18097 3 2 Lin
25. ur program can issue a scanner command to alter the list An exchange or an adapter scan is the scanner s interchange of information with one adapter During an exchange the scanner receives data and status information from the adapter and sends data and commands to the adapter The PC I O Scanner performs a discrete transfer of I O data during the same exchange If the adapter s chassis contains a block transfer module that is ready a block transfer will be performed Figure 3 4 The Process of Refreshing the I O image Tables During an I O Scan i Host Scanner VORefeh T Scan Beginning of Scan Adapter Interrupt Host N l I l I l 1 i I l l l l 1 18149 After servicing an adapter the scanner looks at its command queue to see if any management commands are waiting If so and if the current operating mode allows the scanner executes one management command If the scanner had a confirmation of this command or of a previously executed command it puts the confirmation in the dual port RAM and interrupts the host CPU 3 9 Chapter 3 PC I O Operation 3 10 The scan list is circular Each time the scanner reaches the end of the scan list it starts again at the beginning A scan is one complete cycle by the scanner through the scan list from any point to the same point Each time the host CPU interrupts the scanner the scanner puts a marker in the sca
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