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1. 2 THEN PRINT Not sysctrl 10020 IF status 3 THEN PRINT Not ctrlinchg 10030 IF status 4 THEN PRINT Ctrlinchg 10040 IF status 5 THEN PRINT Interface clear 10050 IF status 6 THEN PRINT Sherror 10060 IF status 7 THEN PRINT Timeout 10070 IF status 8 THEN PRINT Byte count 0 10080 IF status 9 THEN PRINT Sysctrl 10090 IF status 10 THEN PRINT Buffer full 10100 IF status 11 THEN PRINT Buffer overflow 10110 IF status 12 THEN PRINT Unrecognised SWI 10120 IF status 13 THEN PRINT Unrecognised command Line 1050 specifies the end of string character for output as CR carriage return ASCII code 13 which is required by the instrument Line 1060 specifies the end of string character for input as CR carriage return ASCII code 13 which is sent by the instrument It is only necessary to define the end of string characters if they differ from the default CR carriage return LF line feed Line 1070 enable timeouts Timeouts are particularly useful during program development Line 1080 initialises the interface hardware sends REN remote enable true and IFC interface clear true for approximately 650 microseconds The Computer becomes controller in charge Line 1090 addresses device 16 to listen and outputs the string FOT1R3X in mode 0 ie the end of string character specified on line 1050 is appended Line 1100 addresses device 16 to talk and inputs up to 255 character
2. le on disc RS buffers tatus FNXadrextandoutputmem 1 9 1 buffer s 512 E status lt gt 0 THEN 10000 Line 1050 reserves 512 bytes of memory for the trace Line 1080 addresses device with primary address 9 and secondary address 1 the oscilloscope to talk and inputs 512 bytes of data in mode 2 and stores it in memory starting it at address buffer Line 3000 addresses device with primary address 9 and secondary address 1 the oscilloscope to listen and outputs 512 bytes of data in mode 1 ie EOI end or identify is set true with the last data byte 4 4 Data Transfer between Devices If it is required to transfer data between devices one talker and one or more listeners without involving the Computer the following sequence should be used Example To abort on error 1000 RI 1010 REM data transfer EM computer configured as system controller 1020 REM abort on error 1030 1040 PROCinit 1050 PROCunlisten 1060 PROCtalk 7 1070 PROClisten 6 1080 PROCatn_false 2000 REPEAT UNTIL FNservice requested 2010 statusbyte FNserial_poll 7 To return error status 1000 REM computer configured as system controller 1010 REM data transfer 1020 REM return error status 1030 1040 status FNXinit 1045 IF status lt gt 0 THEN 10000 1050 status FNXunlisten 1055 IF status lt gt 0 THEN 10000 1060
3. 1085 IF status lt gt 0 THEN 10000 1090 PRINT Message received message 1100 status FNXoutput 0 ACORN ARCHIMEDES 1105 IF status lt gt 0 THEN 10000 Line 1050 specifies the end of string character for input as LF line feed ASCII code 10 Line 1060 specifies the end of string character for output as LF line feed ASCII code 10 Line 1070 or 1070 1077 delays the program until IFC interface clear has been received from the system controller Line 1080 inputs up to 255 characters when the Computer is addressed to listen by the controller in charge in mode 0 ie until the end of string character specified on line 1050 is received and returns it in the variable message Line 1100 outputs the string ACORN ARCHIMEDES when the Computer is addressed to talk by the current controller in charge in mode 0 ie the end of string character specified on line 1060 is appended 5 2 Data Input and Output directly to and from memory Example To abort on error 1000 REM computer configured as simple talker listener 1010 REM data input and output 1020 REM binary coded data directly to and from memory 1030 REM abort on error 1040 1050 DIM buffer 2047 1060 REPEAT UNTIL FNinterface_cleared 1070 PROCinputmem 1 buffer 2048 1080 1090 REM save data in file on disc 1100 1110 OSCLI SAVE data STRS buffer 800 1120 3000 REM load data from file on disc 3010 3020 OSCLI LOAD data STRS buf
4. 2 2 The Computer as a Simple Talker Listener 3 The IEEE488 Interface Software 3 1 Features of the Interface Software 3 1 1 Error Status 3 1 2 Output Modes 3 1 3 Input Modes 3 1 4 End of String Characters for Output 3 1 5 End of String Characters for Input 3 1 6 Timeouts 4 The Computer as Controller in Charge 4 1 Data Output and Input strings of up to 255 characters 4 1 1 Device with Primary Address Only 4 1 2 Device with Primary and Secondary Address 4 2 Converting between String and Numeric Variables 4 3 Data Output and Input directly from and to memory 4 3 1 Device with Primary Address Only 4 3 2 Device with Primary and Secondary Address 4 4 Data Transfer between Device 4 5 Determining the Status of a Device 4 5 1 Serial Poll 4 5 2 Parallel Poll 4 6 Initialising Devices 4 7 Triggering Devices 4 8 Remote and Local Operation of Device 4 9 Passing Control to Another Device 5 The Computer as a Simple Talker Listener 5 1 Data Input and Output strings of up to 255 characters 5 2 Data Input and Output directly to and from memory 5 3 Requesting Service from the Controller in Charge 6 BASIC Procedures and Functions 7 Using the IEEE488 Interface from Assembler 8 Hardware References Appendices Expansion Card DIP Switch Settings I IEEE488 Interface Commands Ill Parallel Poll Response Byte IV IEEE488 Errors V Interface Specification VI BASIC Procedures and Functions 1 Introduction Before using the IEEE488 Interface Ex
5. ON OFF ON OFF OFF ON 6 OFF ON ON OFF OFF ON 7 ON ON ON OFF OFF ON 9 ON OFF OFF ON OFF ON 0 OFF ON OFF ON OFF ON 1 ON ON OFF ON OFF ON 2 OFF OFF ON ON OFF ON 3 ON OFF ON ON OFF ON 4 OFF ON ON ON OFF ON 5 ON ON ON ON OFF ON 6 OFF OFF OFF OFF ON ON 7 ON OFF OFF OFF ON ON 8 OFF ON OFF OFF ON ON 9 ON ON OFF OFF ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON ON OFF OFF OFF OFF ON ON ON ON ON ON ON ON ON ON ON OFF OFF OFF OFF ON ON ON OFF OFF ON OFF ON 20 ON OFF OFF ON ON OFF OFF ON OFF OFF OFF OFF 21 22 23 24 ON ON 25 26 ON 27 28 ON 29 OFF 30 Note address 31 is not permitted
6. 105 IF status lt gt 0 THEN 10000 Line 1090 addresses device with primary address 6 and secondary address 3 to listen and outputs the string FOT1R3X in mode 0 ie the end of string character specified on line 1050 is appended Line 1100 addresses device with primary address 6 and secondary address 3 to talk and inputs data in mode 0 ie until the end of string character specified on line 1060 is received and returns it in the variable data 4 2 Converting between String and Numeric Variables In order to use data that has been input as a string of ASCII characters in subsequent calculations it must be converted from a string to a real or integer variable To convert from a string to a real variable reading VAL reading If the string has a prefix or suffix then this must be stripped off prior to conversion To convert from a string of format V n nE nn to a real variable reading VAL RIGHTS readingS LEN reading 1 To convert from a real variable to a string variable valueS STRS value 4 3 Data Output and Input directly from and to memory Some devices such as spectrum analysers digital storage oscilloscopes and other microprocessor based instruments with their own memory can receive and send long fixed length sequences of binary coded data These are often longer than the maximum 255 characters that can be stored in a string and therefore modes 1 or 2 are normally used when outputti
7. 4 if required fit a joiner and blanking plate 6 Reconnect the Computer to the mains supply 7 Switch on the power to the Computer 8 Confirm that the card has been fitted correctly by typing PODULES This should list the IEEE488 Interface as Intelligent Interfaces IEEE488 Interface together with any other cards fitted Only one IEEE488 Interface Expansion Card can be fitted 1 3 Connecting Devices to the Computer Before connecting devices to the Computer ensure that the power to both the Computer and the devices is switched off The Computer can be connected to up to 14 other devices using IEEE488 standard cable assemblies These have a plug and socket at each end permitting star or linear interconnection of devices The connectors are provided with two securing screws which allow them to be stacked on the socket of each device The IEEE488 socket is normally found on the rear of a device The IEEE488 standard permits individual cable lengths of up to 4m and a total cable length in a system of 2m per device or 20m whichever is the shorter When all devices have been connected to the Computer switch on the power to the devices and then the Computer 1 4 The Scope of the User Guide This User Guide does not attempt to reproduce the IEEE 488 Standard or explain every aspect of it The interested user is referred to Ref 1 However this User Guide provides all the information required to use the Acorn Archimedes Co
8. IEEE488 Interface Expansion Card for Acorn RISC OS based Computers User Guide Intelligent Interfaces November 1995 C Copyright Intelligent Interfaces Ltd 1988 Neither the whole or any part of the information contained in this User Guide may be adapted or reproduced in any material form except with the written approval of Intelligent Interfaces Ltd All information is given by Intelligent Interfaces in good faith However it is acknowledged that there may be errors or omissions in this User Guide Intelligent Interfaces welcomes comments and suggestions relating to the IEEE488 Interface Expansion Card and this User Guide All correspondence should be addressed to Technical Enquiries Intelligent Interfaces Ltd P O Box 80 Eastleigh Hampshire S053 2YX Tel 023 8026 1514 Fax 087 0052 1281 This User Guide is intended only to assist the reader in the use of the IEEE488 Interface Expansion Card and therefore Intelligent Interfaces shall not be liable for any loss or damage whatsoever arising from the use of any information or particulars in or any error or omission in this User Guide or any incorrect use of the interface CONTENTS 1 Introduction 1 1 Setting the IEEE488 Address of the Computer 1 2 Fitting the Expansion Card 1 3 Connecting Devices to the Computer 1 4 The Scope of the User Guide 2 The IEEE488 Standard 2 1 IEEE488 Device Addresses 2 2 Types of IEEE488 Devices 2 2 1 The Computer as System Controller 2
9. OVS R15 R14 errormessage EQUS IEEE488 error CHR 10 CHRS 13 EQUB amp 00 beginoutputdata EQUS FOTIR3X endoutputdata begininputdata 1510 EQUS STRINGS 9 1520 endinputdata 1530 J 1540 NEXT pass 1550 CALL code Line 1050 defines the IEEE488 SWI Lines 1060 1130 defines the IEEE488 command numbers Lines 1180 1230 specify the end of string character for output and input as LF line feed ASCII code 10 Lines 1240 1250 enable timeouts Lines 1252 1270 initialises the interface hardware sends REN remote enable and IFC interface clear true for approximately 650 microseconds The Computer becomes controller in charge Lines 1280 1350 addresses device 16 to listen and outputs the string FOT1R3X from memory beginning at beginoutputdata in mode 0 ie the end of string character specified by lines 1180 1230 is appended Lines 1360 1430 addresses device 16 to talk and inputs up to 9 characters in mode 0 ie until the end of string character specified by lines 1180 1230 is received and places them in memory beginning at begininputdata If an error occurs both of the above examples produce a similar result ie an error message is displayed However in practice the return error status SWI can be used to trap errors in the program and take the appropriate corrective action 8 Hardware The interface uses the Texas Instruments TMS9914A GPIB Adapter together with the SN75160A and SN75162A octal GPIB transce
10. Service from the Controller in Charge If the Computer requires action from the controller in charge for example it has completed a series of calculations and has the results ready for output it can request service from the controller in charge by sending SRQ service request The controller in charge conducts a serial poll to determine which device or devices are requesting service Each device in a system with a serial poll capability is polled in turn When the Computer is polled it returns a single STB status byte If the Computer is requesting service bit 6 the RQS request service bit is set The user must specify the meaning of the other seven bits of the status byte To request service from the controller in charge PROCrequest_service 3 or status FNXrequest_service 3 sets the least two significant bits of the STB status byte Following the reading of the STB status byte by the controller in charge during a serial poll the RQS request service bit is cleared and SRQ service request is sent false automatically 6 BASIC Procedures and Functions The text file Docs Chap6 on the distribution disc describes in alphabetical order the BASIC procedures and functions under the following headings Purpose A description of what the procedure or function does Syntax A formal declaration of both the abort on error form and the return error status form of the procedure or function Parameters A list of the p
11. al bit parallel The IEEE Standard specifies a 24 pin Micro ribbon connector whereas the IEC Publication specifies a 25 pin D type connector as used for the EIA RS232 C data communication interface 2 1 IEEE488 Device Addresses Up to 15 devices can be connected together to form an IEEE488 system Each device must have a unique address Some devices have only one address a primary address whilst others have an extended address a primary and a secondary address Primary and secondary addresses may be in the range 0 to 30 Secondary addresses are often used to select different functions within the same device eg an analogue to digital converter with a number of analogues inputs may have the input selected by the secondary address Most devices are delivered with factory set primary and secondary addresses These can be found in the manufacturer s manual If a number of devices in a system have the same address then these must be changed by following the manufacturer s instructions Usually this involves changing DIP switch settings on the rear of the device 2 2 Types of IEEE488 Devices A device can have the ability to send data act as a talker receive data act as a listener or do both act as a talker listener Some devices also have the ability to manage the system act as a controller in charge although there can only be one device acting as the controller in charge at any time Only one device in an IEEE488 system can act as the syste
12. arameters required giving their type range and if necessary additional information on their specification Results A list of the results returned giving their type range and if necessary additional information Example Example to illustrate the use of both the abort on error form and the return error status form of the procedure or function For clarity the parameters of procedures are shown as constants However variables of the same type can be used Notes Give details of the operation of the interface software and when a procedure or function has the same effect as a number of lower level procedures or functions these are listed Remote messages Shows the logical state of the ATN attention uniline message together with the multiline messages sent and received LAD represents a listen address of a specific device TAD represents a talk address of a specific device 7 Using the IEEE488 Interface from Assembler Read the Archimedes Programmer s Reference Manual particularly the sections on Fundamental Operating System Concepts and Appendix A on ARM Assembler before writing programs in assembler General information on communicating with the operating system is given in the Programmer s Reference Manual The IEEE488 interface software is a relocatable module which extends the operating system The facilities of the IEEE488 interface are accessed through a single Intelligent Interfaces IEEE488 SWI software interrupt numb
13. er amp 40340 error generating or amp 60340 error returning allocated by Acorn Computers If an error occurs in an error generating SWI on return the V flag is set and register RO contains a pointer The pointer is to an error block The format of the error block is first four bytes a word giving the error number subsequent bytes a string terminated by a zero byte giving the error message The error number is formed by combining the IEEE488 error identifier 300800600 allocated by Acorn Computers and an IEEE488 interface software basic error number Appendix IV lists the IEEE488 errors Parameters are passed and results are returned in the processor s registers Appendix II gives the allocation of parameters and results to the processor s registers All commands share the same structure On entry RO is undefined R1 is command number R2 R7 parameters On exit RO points to an error block R1 is preserved R2 R7 parameters are preserved results are updated Example To abort on error 000 REM computer configured as system controller 010 REM data output and input 020 REM abort on error 030 040 DIM code 256 050 IEEE488 amp 40340 060 specwreos amp 03 070 specrdeos amp 04 080 retryons amp 06 085 init SUA 087 sre SUE 1090 ifc amp 0D 1100 specwrmode S amp 08 ba ba ba ba ba ba ba ba ba ba bo 1110 specrdmode amp 09 1120 adrtolistenwrdataunlgts amp 3C 1130 adrto
14. erences Ref 1 Ref 2 ANSI IEEE Std 488 1978 Revision of ANSI IEEE Std 488 1975 includes supplement IEEE Std 488A 1980 IEEE488 Standard Digital Interface for Programmable Instrumentation The Institute of Electrical and Electronic Engineers Inc 1978 TMS 9914 GPIB Adapter Data Manual Texas Instruments Appendix I EXPANSION CARD DIP SWITCH SETTINGS Computer Configured as the System Coniroller Address SW1 SW2 SW3 SW4 SW5 SW6 0 OFF OFF OFF OFF OFF OFF 1 ON OFF OFF OFF OFF OFF 2 OFF ON OFF OFF OFF OFF 3 ON ON OFF OFF OFF OFF 4 OFF OFF ON OFF OFF OFF 5 ON OFF ON OFF OFF OFF 6 OFF ON ON OFF OFF OFF 7 ON ON ON OFF OFF OFF 9 ON OFF OFF ON OFF OFF 10 OFF ON OFF ON OFF OFF 11 ON ON OFF ON OFF OFF 12 OFF OFF ON ON OFF OFF 13 ON OFF ON ON OFF OFF 14 OFF ON ON ON OFF OFF 15 ON ON ON ON OFF OFF 16 OFF OFF OFF OFF ON OFF 17 ON OFF OFF OFF ON OFF 18 OFF ON OFF OFF ON OFF 19 ON ON OFF OFF ON OFF 20 OFF OFF ON OFF ON OFF 21 ON OFF ON OFF ON OFF 22 OFF ON ON OFF ON OFF 23 ON ON ON OFF ON OFF 24 OFF OFF OFF ON ON OFF 25 ON OFF OFF ON ON OFF 26 OFF ON OFF ON ON OFF 27 ON ON OFF ON ON OFF 28 OFF OFF ON ON ON OFF 29 ON OFF ON ON ON OFF 30 OFF ON ON ON ON OFF Note address 31 is not permitted Computer Configured as a Simple Talker Listener Address SW1 SW2 SW3 SW4 SW5 GO 0 OFF OFF OFF OFF OFF ON 1 ON OFF OFF OFF OFF ON 2 OFF ON OFF OFF OFF ON 3 ON ON OFF OFF OFF ON 4 OFF OFF ON OFF OFF ON 5
15. fer 3030 3040 PROCoutputmem 1 buffers 2048 To return error status 1000 REM computer configured as simple talker listener 1010 REM data input and output 5 2 1020 REM binary coded data directly to and from memory 1030 REM return error status 1040 1050 DIM buffer 2047 1060 REPEAT 1062 status FNXinterface_cleared state 1065 IF status lt gt 0 THEN 10000 1067 UNTIL state 1070 status FNXinputmem 1 buffer 2048 1075 IF status lt gt 0 THEN 10000 1080 1090 REM save data in file on disc 1100 1110 OSCLI SAVE data STRS buffer s 800 1120 3000 REM load data from file on disc 3010 3020 OSCLI LOAD data STRS buffer 3030 3040 status FNXoutputmem 1 buffers 2048 3045 IF status lt gt 0 THEN 10000 Line 1050 reserves 2048 bytes of memory for the data Line 1060 or 1060 1067 delays the program until IFC interface clear has been received from the system controller Line 1070 inputs up to 2048 bytes of data when the Computer is addressed to listen by the current controller in charge in mode 1 ie until EOI end or identify true is received with a data byte and stores it in memory starting at address buffer Line 3040 outputs 2048 bytes of data from memory starting at address buffer when the Computer is addressed to talk by the current controller in charge in mode 1 ie EOI end or identify is set true with the last data byte 5 3 Requesting
16. file XBAS488 which return an error status can be used to trap errors within a program and then take the appropriate action This makes it possible to recover from an error when it occurs within a procedure function or loop The error status returned is an IEEE488 Interface Software basic error number These are listed in Appendix IV Some functions particularly those not associated with bus activity always return an error status of 0 indicating that no IEEE488 error has occurred Therefore for these functions the return error status form does not offer any advantage over the abort on error form 3 1 2 Output Modes When the interface software outputs data it can do so in one of four modes Mode 0 output data and append end of string character or characters Mode 1 output data and send EOI end or identify true with the last data byte Mode 2 output n data bytes Mode 3 output data and append end of string character or characters and set EOI true with the last end of string character 3 1 3 Input Modes When the interface software inputs data it can do so in one of four modes Mode 0 input data until end of string character or characters are received Mode 1 input data until EOI end or identify true is received with a data byte 3 1 Mode 2 input n data bytes Mode 8 input data until end of string character or characters are received and or until EOI true is received with a data byte The most commonly used mode for both
17. he delimiting character or characters that the device sends In modes 0 or 3 data is input until one or two end of string characters are received The interface software defaults to two end of string characters CR carriage return ASCII code 13 and LF line feed ASCII code 10 To redefine the end of string characters as LF CR PROCeos_in_2chr 10 13 or status FNXeos in 2chr 10 13 or to define a single end of string character as LF PROCeos_in_lchr 10 or status FNXeos_in_lchr 10 3 1 6 Timeouts As timeouts are not part of the IEEE488 standard the interface software defaults to timeout off However it is recommended particularly during program development that timeouts are used To enable timeouts PROCtimeout_on or status FNXtimeout_on The default timeout period is approximately eight seconds To redefine the timeout period as 20 seconds PROCtimeout_period 20 or status FNXtimeout_period 20 To disable timeouts PROCtimeout_off or status FNXtimeout_off 4 The Computer as Controller in Charge The Computer acts as the controller in charge if Switch 6 of the DIP switch on the Expansion Card is in the off position ie it is the system controller and the Computer has sent IFC interface clear or as a simple talker listener the current controller in charge passes control back to it This process is transparent to the user and can occur at any time To determine whether the Computer is contro
18. ivers The TMS9914A interfaces the Computer to the IEEE488 bus It relieves the processor of the task of handling IEEE488 protocol when commands and data are sent and received and implements most of the IEEE488 functions If processor intervention is required in order to support a function the TMS9914A generates an interrupt The IEEE488 interface software utilises these features to for example allow the Computer to be remotely configured to enable it to take part in a parallel poll in a way that is transparent to the user A 5 MHz crystal provides the TMS9914A with a clock for timing purposes at the maximum permitted frequency This results in the highest possible data transfer rates The SN75160A uses tri state drivers to drive the data lines of the bus except during a parallel poll when it automatically switches to open collector drivers The Expansion Card has a 6 way DIP Switch Switches 1 5 specify the IEEE488 Interface Address of the Computer Switch 6 specifies whether the Computer is either the system controller off or a simple talker listener on Appendix lists the DIP switch settings The interface software is stored in a paged ROM and is automatically loaded and initialised by the operating system when the Computer is switched on or reset The three option selection links S1 S2 and S3 are provided to enable different sizes of EPROM to be fitted Size Kbyte S1 52 S3 8 A A N A 16 A A N A 32 B A N A 64 B B A 128 B B B Ref
19. ll the least significant four bits of the PPE parallel poll enable byte the S P3 P2 and P1 bits specify the sense and assigned bit in the PPR parallel poll response byte as shown by the table in Appendix III To remotely configure a device enable it to take part in a parallel poll Example To abort on error 2500 PROCparallel_poll_unconfigure 2510 PROCparallel_poll_enable 4 12 or to return error status 2500 status FNXparallel_poll_unconfigure 2505 IF status lt gt 0 THEN 10000 2510 status FNXparallel_poll_enable 4 12 2515 IF status lt gt 0 THEN 10000 Line 2500 ensures that all devices with a parallel poll capability are unconfigured and are therefore unable to take part in a subsequent parallel poll until enabled Line 2510 enables the device with address 4 to take part in a parallel poll The table in Appendix III shows that the S sense bit 3 is set and PPR5 parallel poll response is specified by the integer 12 During a parallel poll each enabled device compares its internal individual status bit with the sense bit it received when it was enabled If they are the same the bit assigned to that device is set in the parallel poll response byte To conduct a parallel poll response FNparallel_poll or status FNXparallel_poll responses returns the PPR parallel poll response byte in the variable response To remotely disable the device with addres
20. ller in charge state FNcontroller_in_charge or status FNXcontroller in charge state returns the logical state TRUE in the variable state if the Computer is the controller in charge 4 1 Data Output and Input strings of up to 255 characters 4 1 1 Device with Primary Address Only Example To abort on error 1000 REM computer configured as system controller 1010 REM data output and input 1020 REM strings of up to 255 characters 1030 REM abort on error 1040 1050 PROCeos out 1chr 13 1060 PROCeos in 1chr 13 1070 PROCtimeout_on 1080 PROCinit 1090 PROCadrandoutput 0 16 FOTIR3X 1100 data FNadrandinput 0 16 255 or to return error status 1000 REM computer configured as system controller 1010 REM data output and input 1020 REM strings of up to 255 characters 1030 REM return error status 1040 1050 status FNXeos_out_lchr 13 1055 IF status lt gt 0 THEN 10000 1060 status FNXeos_in_lichr 13 1065 IF status lt gt 0 THEN 10000 1070 status FNXtimeout_on 1075 IF status lt gt 0 THEN 10000 1080 status FNXinit 1085 IF status lt gt 0 THEN 10000 1090 status FNXadrandoutput 0 16 FOT1R3X 1095 IF status lt gt 0 THEN 10000 1100 status FNXadrandinput data 0 16 255 4 1 1105 IF status lt gt 0 THEN 10000 10000 IF status 1 THEN PRINT Not initialised 10010 IF status
21. m controller This device and only this device has the ability to send REN remote enable and IFC interface clear and then operate as the first controller in charge The Computer is normally the system controller 2 2 1 The Computer as System Controller The Computer can be configured as the system controller by setting DIP Switch 6 on the Expansion Card to the off position As the system controller the Computer can send REN remote enable and IFC interface clear and then operate as the controller in charge As controller in charge the Computer manages the interface It can address itself and other devices to talk and listen and then input and output data It can send all addressed commands eg GTL go to local and all universal commands eg LLO local lockout It can conduct both serial and parallel polls and pass control to another device 2 2 2 The Computer as a Simple Talker Listener The Computer can be configured as a simple talker listener by setting DIP Switch 6 on the Expansion Card to the on position As a talker listener the Computer can when addressed by the controller in charge input and output data It can specify the serial poll STB status byte and RQS request service It can take part in a serial poll and be remotely configured to take part in a parallel poll It can become controller in charge if control is passed to it by the current controller in charge 3 The IEEE488 Interface Software The interface software is a rel
22. mputer fitted with an Intelligent Interfaces IEEE488 Interface Expansion Card with any other IEEE488 device when programming in BBC BASIC or ARM Assembler Separate libraries of procedures are available from Intelligent Interfaces to simplify the use of the interface from FORTRAN 77 and ANSI C Details are given in the User Guide supplied with each library 2 The IEEE488 Standard The IEEE488 Interface is a general purpose system for exchanging digital data in bit parallel byte serial form between a number of devices eg digital voltmeters digital oscilloscopes spectrum analysers transient data recorders function generators etc in a local area The original concept was developed by Hewlett Packard who called it the HP IB Hewlett Packard Interface Bus The IEEE Institute of Electrical and Electronics Engineers first produced a standard in 1975 IEEE Std 488 1975 This was revised in 1978 as IEEE Std 488 1978 A supplement was included in 1980 IEEE Std 488A 1980 In 1987 the IEEE re designated IEEE Std 488 as IEEE Std 488 1 and published a draft standard IEEE Std 488 2 Codes Formats Protocols and Common Commands for use with IEEE Std 488 1 The interface is identical apart from the mechanical connection system to that described in the IEC International Electrotechnical Commission Publication IEC 625 1 and BSI British Standards Institute Publication BS6146 Part 1 1981 AO interface system for programmable measuring instruments byte seri
23. mputer is system controller state FNsystem_controller or status FNXsystem controller state returns the logical state TRUE in the variable state if the Computer is system controller To pass control to a device with address 4 which has the capability to become controller in charge PROCpass_control 4 or status FNXpass_control 4 The Computer then acts as a talker listener It can become controller in charge again if either the current controller in charge passes control back by addressing the Computer to talk and sending TCT take control This process is transparent to the user and can occur at any time or if the Computer is the system controller it sends IFC interface clear To determine whether the Computer is controller in charge state FNcontroller_in_charge or status FNXcontroller_in_charge state returns the logical state TRUE in the variable state if the Computer is controller in charge 5 The Computer as a Simple Talker Listener The Computer acts as a talker listener if Switch 6 of the DIP switch on the Expansion Card is in the on position ie it is not the system controller or as controller in charge it has passed control to another device To determine whether the Computer is a talker listener state FNcontroller_in_charge or status FNXcontroller_in_charge state returns the logical state FALSE in the variable state if the Computer is a talker listener The system controlle
24. nd stores it in the display buffer of the analyser 4 3 2 Device with Primary and Secondary Address Example To abort on error 1000 REM computer configured as system controller 1010 REM data output and input 1020 REM binary coded data directly from and to memory 1030 REM abort on error 1040 1050 DIM buffer 511 1060 PROCtimeout_on 1070 PROCinit 1080 PROCadrextandinputmem 2 9 1 buffer S 512 4 5 1090 1100 1110 1120 2960 2970 2980 2990 3000 R O R O EM save data in file SCLI SAVE trace S1 EM load data from fil SCLI LOAD trace TZEI on disc RS buffers 200 le on disc RS buffers PROCadrextandoutputmem 1 9 1 buffer 512 To return error status 1000 1010 1020 1030 1040 1050 1060 1065 1070 1075 1080 1085 1090 1100 1110 1120 2960 2970 2980 2990 3000 3005 Ki D bi DO Ki D D R O R O S I W D w e Hee E Ss Es zZ K binary coded data IM buffer 511 tatus FNXinit EM save data in file SCLI SAVE trace S1 EM load data from fil SCLI LOAD trace TZEI computer configured as system controller data output and input directly from and to memory return error status tatus FNXtimeout_on F status lt gt 0 THEN 10000 E status lt gt 0 THEN 10000 tatus FNXadrextandinputmem 2 9 1 buffer s 512 E status lt gt 0 THEN 10000 on disc RS buffers 200
25. ng or inputting data 4 3 1 Device with Primary Address Only The following example is part of a program that was written for a Hewlett Packard HP3582A Spectrum Analyzer in order to read the display of the analyser save it in a file on disc and at a later stage load it from the file on disc and write it to the display of the analyser 4 3 Example To abort on error 1000 1010 1020 1030 1040 1050 1060 1070 1080 1090 1100 1110 1120 1130 1140 1150 1160 1170 2960 2970 2980 2990 3000 3010 3020 3030 REM computer configured as system controller REM data output and input REM binary coded data directly from and to memory REM abort on error DIM buffer 1025 displaystate S buffer display buffer 2 PROCtimeout_on PROCinit PROCadrandoutput 0 11 HLTLFM 77455 1 PROCadrandinputmem 2 11 displaystate 2 PROCadrandoutput 0 11 LFM 74000 512 PROCadrandinputmem 2 11 display 1024 REM save data in file on disc OSCLI SAVE display STR buffer 402 REM load data from file on disc OSCLI LOAD display STRS buffer PROCadrandoutput 0 11 HLTWIM 77455 1 PROCadrandoutputmem 2 11 displaystate 2 PROCadrandoutput 0 11 WIM 74000 512 PROCadrandoutputmem 2 11 display 1024 To return error status 1000 1010 1020 1030 1040 1050 1060 1070 1080 1085 1090 1095 1100 1105 1110 1115 1120 1125 1130 1135 1140 1150 1160 1170 REM computer configured a
26. ocatable module which extends the operating system to enable IEEE488 interface operation The module is stored in ROM on the Expansion Card and is automatically loaded and initialised by the operating system when the Computer is switched on or reset by pressing lt Ctrl gt lt RESET gt If the Computer is configured as the system controller it sends REN remote enable true and IFC interface clear true for approximately 650 microseconds and becomes the controller in charge To check that the module has been loaded type MODULES This lists all the modules present Once initialised the interface software remains active until the module is either deleted or re initialised To delete the module type RMKILL IBEE488 The extensive facilities of the IEEE488 interface software can be accessed through the single Intelligent Interfaces IEEE488 SWI SoftWare Interrupt instruction amp 40340 allocated by Acorn Computers To simplify the use of the interface from BASIC two libraries of BASIC procedures and functions are supplied on the software distribution disc Those in the file BAS488 in the directory BASICProcs abort on error whereas those in the file XBAS488 in the directory BASICProcs return an error status The procedures and functions can be INSTALLed in a BASIC library gt INSTALL S BASTICProcs BAS488 or gt INSTALL S BASICProcs XBAS488 3 1 Features of the Interface Software 3 1 1 Error Status The functions in the
27. pansion Card check that the following items in addition to this User Guide have been received IEEE488 Interface Expansion Card Software Distribution Disc If any item is missing contact the supplier 1 1 Setting the IEEE488 Address of the Computer Switches 1 to 5 of the DIP switch on the IEEE488 Interface Expansion Card specify the IEEE488 Interface address of the Computer Switch 6 of the DIP switch specifies whether the Computer is either the system controller off or a simple talker listener on The Expansion Card is supplied with all switches in the off position ie the address of the Computer is 0 and it is the system controller Normally it is not necessary to change these settings However if another device has an address of 0 or it is required to use the Computer as a simple talker listener refer to Appendix which lists the DIP switch settings 1 2 Fitting the Expansion Card The card can be fitted in any Acorn Computer with an expansion backplane The card can be fitted in the external expansion card socket of an A3000 computer To fit the card in an A300 series A400 series A540 A5000 Risc PC or A7000 computer 1 Switch off the power to the Computer 2 Disconnect the Computer from the mains supply 3 The card can be fitted in any unused expansion card slot 4 Remove the blanking plate from the rear of the Computer and retain the two screws 5 Fit the card and secure it in position using the two screws retained at stage
28. pecwreos amp 03 specrdeos amp 04 retryons amp 06 init amp 0A sreS amp 0E ifc SUD specwrmode S amp 08 specrdmode S amp 09 adrtolistenwrdataunlgts amp 3C 7 2 1130 1140 1150 1160 1170 1180 1190 1200 1210 1215 1220 1230 1235 1240 1250 1251 1252 1254 1255 1256 1258 1259 1260 1270 T279 1280 1290 1300 1305 1310 1320 1330 1340 1350 1355 1360 1370 1380 1385 1390 1400 1410 1420 1430 1435 1440 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1470 1480 1490 1500 adrtotalkrddatauntgts amp 3D FOR pass 0 TO 2 STEP 2 code OPT _ pass MOV R1 Specwreos MOV R2 1 MOV R3 10 SWI XIEEE488 BVS error MOV R1 specrdeos SWI XIEEE488 BVS error MOV R1 retryon SWI XIEEE488 BVS error MOV R1 init SWI XIEEE488 BVS error MOV R1 beren SWI XIEEE488 BVS error MOV R1 ifc SWI XIEEE488 BVS error MOV R1 Specwrmode MOV R2 0 SWI XIEEE488 BVS error MOV R1 adrtolistenwrdataunlgts MOV R3 16 ADR R5 beginoutputdata MOV R6 endoutputdata beginoutputdata SWI XIEEE488 BVS error MOV R1 Specrdmode MOV R2 0 SWI XIEEE488 BVS error MOV R1 adrtotalkrddatauntgts MOV R3 16 ADR R5 begininputdata MOV R6 endinputdata begininputdata SWI XIEEE488 BVS error MOVS R15 R14 error ADR RO errormessage SWI OS_Write0O M
29. puter for example it has completed a measurement it can request service from the Computer by sending SRQ service request To determine whether a device or devices are requesting service states FNservice_requested or status FNXservice requested state returns the logical state TRUE in the variable state if a device or devices are requesting service A serial poll is conducted to determine which device or devices are requesting service Each device in a system with a serial poll capability must be polled in turn When a device is polled it returns a single STB status byte If bit 6 is set then the device is sending RQS request service The manufacturer s manual for a device must be consulted to determine the meaning of the other 7 bits of the status byte To conduct a serial poll of the device with address 10 statusbyte S FNserial_poll 10 or status FNXserial_poll statusbyte 10 returns the STB status byte in the variable statusbyte During a serial poll each device must be polled separately Therefore a serial poll is time consuming 4 5 2 Parallel Poll A parallel poll is a rapid way of determining whether a device or devices require action by the Computer Before a parallel poll is conducted those devices that are to take part must be assigned a bit in the parallel poll response byte This is done either remotely or locally When a device is remotely configured to enable it to take part in a parallel po
30. r normally sends IFC interface clear to return the interfaces of all the devices on the bus to a known initial state To determine whether the Computer has received IFC interface clear state FNinterface_cleared or status FNXinterface_cleared stateS returns the logical state TRUE in the variable state if the Computer has received IFC interface clear 5 1 Data Input and Output strings of up to 255 characters Example To abort on error 1000 REM computer configured as simple talker listener 1010 REM data input and output 1020 REM strings of up to 255 characters 1030 REM abort on error 1040 1050 PROCeos_in_lichr 10 1060 PROCeos_out_lchr 10 1070 REPEAT UNTIL FNinterface_cleared 1080 message FNinput 0 255 1090 PRINT Message received message 1100 PROCoutput 0 ACORN ARCHIMEDES to return error status 1000 REM computer configured as simple talker listener 1010 REM data input and output 1020 REM strings of up to 255 characters 1030 REM return error status 1040 1050 status FNXeos_in_lchr 10 5 1 1055 IF status lt gt 0 THEN 10000 1060 status FNXeos_out_lchr 10 1065 IF status lt gt 0 THEN 10000 1070 REPEAT 1072 status FNXinterface_cleared state 1075 IF status lt gt 0 THEN 10000 1077 UNTIL state TRUE 1080 status FNXinput message 0 255
31. s 4 from taking part in a parallel poll PROCparallel_poll_disable 4 or status FNXparallel_poll_disable 4 If a data transfer which does not involve the Computer is taking place when a parallel poll is conducted data loss or corruption can occur as the Computer sets ATN attention true asynchronously To prevent this ATN attention must be set true synchronously before the parallel poll To resume data transfer after the parallel poll ATN attention must be set false PROCatn_true_sync response FNparallel_poll PROCatn_false or status FNXatn_true_sync IF status lt gt 0 THEN 10000 status FNXparallel_poll IF status lt gt 0 THEN 10000 status FNXatn_false IF status lt gt 0 THEN 10000 4 6 Initialising Devices A device may have been programmed incorrectly or an error may have occurred To clear a device with the capability PROCselected_device_clear 6 or status FNXselected_device_clear 6 initialises the device with address 6 To clear all devices with the capability PROCdevice_clear or status FNXdevice_clear Note that device clear only affects device functions It normally returns a device to its power on state Interface functions are cleared by IFC interface clear 4 7 Triggering Devices To trigger the basic operation of a device with the capability PROCgroup_execute_trigger 14 or status FNXgroup_execute_trigger 14 triggers the device with addre
32. s in mode 0 ie until the end of string character specified on line 1060 is received and returns it in the variable data If an error occurs both of the above examples produce a similar result ie an error message is displayed and the program terminates However in practice the functions that return error status can be used to trap errors within the program and take the appropriate corrective action 4 1 2 Device with Primary and Secondary Addresses Example To abort on error 1000 REM computer configured as system controller 1010 REM data output and input 1020 REM strings of up to 255 characters 1030 REM abort on error 1040 1050 PROCeos_out_lchr 13 P 1060 PROCeos_in_lchr 13 1070 PROCtimeout_on 1080 PROCinit 1090 PROCadrextandoutput 0 6 3 FOTIR3X 1100 dataS FNadrextandinput 0 6 3 255 4 2 or to return error status 1000 REM computer configured as system controller 1010 REM data output and input 1020 REM strings of up to 255 characters 1030 REM return error status 1040 1050 status FNXeos_out_lchr 13 1055 IF status lt gt 0 THEN 10000 1060 status FNXeos_in_ichr 13 1065 IF status lt gt 0 THEN 10000 1070 status FNXtimeout_on 1075 IF status lt gt 0 THEN 10000 1080 status FNXinit 1085 IF status lt gt 0 THEN 10000 1090 status FNXadrextandoutput 0 6 3 FOT1IR3X 1095 IF status lt gt 0 THEN 10000 1100 status FNXadrextandinput data 0 6 3 255 1
33. s system controller REM data output and input REM binary coded data directly from and to memory REM return error status DIM buffer 1025 displaystate S buffer display buffer 2 status FNXtimeout_on IF status lt gt 0 THEN 10000 status FNXinit IF status lt gt 0 THEN 10000 status FNXadrandoutput 0 11 HLTLFM 77455 1 IF status lt gt 0 THEN 10000 status FNXadrandinputmem 2 11 displaystate 2 IF status lt gt 0 THEN 10000 status FNXadrandoutput 0 11 LFM 74000 512 IF status lt gt 0 THEN 10000 status FNXadrandinputmem 2 11 display 1024 IF status lt gt 0 THEN 10000 REM save data in file on disc OSCLI SAVE display STR buffer 402 4 4 2960 REM load data from file on disc 2970 2980 OSCLI LOAD display STRS buffer 2990 3000 status FNXadrandoutput 0 11 HLTWTM 77455 1 3005 IF status lt gt 0 THEN 10000 3010 status FNXadrandoutputmem 2 11 displaystate 2 3015 IF status lt gt 0 THEN 10000 3020 status FNXadrandoutput 0 11 WTM 74000 512 3025 IF status lt gt 0 THEN 10000 3030 status FNXadrandoutputmem 2 11 display 1024 3035 IF status lt gt 0 THEN 10000 Line 1050 reserves 1026 bytes of memory 2 bytes for the displaystate and 1024 byte for the display Line 1100 addresses device 11 the analyser to listen and ou
34. ss 14 4 8 Remote and Local Operation of Devices Following initialisation the Computer as system controller sends REN remote enable true Subsequent addressing of a device to listen changes it from local front panel to remote interface control To return the device with address 9 to local control PROCgo_to_local 9 or status FNXgo_to_local 9 Use of the front panel switches also returns a device to local control To ensure that all devices with the capability only respond to remote interface control PROClocal lockout or status FNXlocal_lockout When a device is in the local lockout state it can be returned to local front panel control by PROCgo_to_local 9 or status FNXgo_to_local 9 To return all devices to local control and clear the local lockout state PROCren_false or status FNXren false To enable remote operation of devices PROCren_true or status FNXren_tru Subsequent addressing of a device to listen will again change it from local to remote operation 4 9 Passing Control to Another Device Only one system controller is permitted in an IEEE488 system and is the only device which can send REN remote enable and IFC interface clear Following initialisation if the Computer is system controller it sends REN remote enable and then IFC interface clear for approximately 650 microseconds and becomes controller in charge It can then manage the system To determine whether the Co
35. status FNXtalk 7 1065 IF status lt gt 0 THEN 10000 1070 status FNXlisten 6 1075 IF status lt gt 0 THEN 10000 1080 status FNXatn_false 1085 IF status lt gt 0 THEN 10000 2000 REPEAT 2002 status FNXservice_requested stateS 2005 IF status lt gt 0 THEN 10000 2007 UNTIL state 2010 status FNXserial_poll statusbyte 7 2015 IF status lt gt 0 THEN 10000 Line 1040 initialises the interface hardware sends REN remote enable true and IFC interface clear true for approximately 650 microseconds The Computer becomes controller in charge Line 1050 unaddresses any active listeners Line 1060 addresses device 7 to talk If another device is addressed to talk it is unaddressed If the device has an extended address PROCtalkext should be used Line 1070 addresses device 6 to listen If the device has an extended address PROClistenext should be used Line 1080 sends ATN attention false The Computer relinquishes active control of the bus and the data transfer commences Often the talker will request service from the controller in charge and indicate in its status byte that the output of data has finished Line 2000 or 2000 2007 determines whether a device or devices are requesting service by sending SRQ service request Line 2010 conducts a serial poll of the device with address 7 the talker 4 5 Determining the Status of a Device 4 5 1 Serial Poll If a device requires action from the Com
36. talkrddatauntgts amp 3D 1140 1150 FOR pass 0 TO 2 STEP 2 1160 P code 1170 OPT pass 1180 MOV R1 specwreos 1190 MOV R2 1 1200 1210 1220 1230 1240 1250 1252 1254 1256 1258 1260 1270 1280 1290 1300 1310 1320 1330 1340 1350 1360 1370 1380 1390 1400 1410 1420 1430 1440 1450 1460 1470 1480 1490 1500 1510 1520 1530 1540 1550 MOV R3 10 SWI IEEE488 MOV R1 Sspecrdeos SWI IEEE488 MOV R1 retryon SWI IEEE488 MOV R1 init SWI IEEE488 MOV R1 sre SWI IEEE488 MOV BL ifc SWI IEEE488 MOV R1 Specwrmode MOV R2 0 SWI IEEE488 MOV R1 adrtolistenwrdataunlgts MOV R3 16 ADR R5 beginoutputdata MOV R6 endoutputdata beginoutputdata SWI IEEE488 MOV R1 Specrdmode MOV R2 0 SWI IEEE488 MOV R1 adrtotalkrddatauntgts MOV R3 16 ADR R5 begininputdata MOV R6 endinputdata begininputdata SWI IEEE488 MOVS R15 R14 beginoutputdata EQUS FOTIR3X endoutputdata begininputdata EQUS STRINGS 9 endinputdata NEXT pass CALL code or to return error status 1000 1010 1020 1030 1040 1050 1055 1060 1070 1080 1085 1087 1090 1100 1110 1120 REM computer configured as system controller REM data output and input REM to return error status DIM code 256 XIEEE488 amp 60340 OS_WriteO amp 02 s
37. the output and input of data is mode 0 This mode is often used by instruments manufactured by Hewlett Packard Keithley Fluke etc Mode 2 is useful when sending or receiving binary coded data particularly directly from and to the memory of the Computer eg when writing to or reading from the memory buffer of a spectrum analyser Mode 1 is used when a device sends or receives EOI end or identify true with the last data byte and is often an alternative to mode 2 Mode 3 was used by the Commodore Business Computers CBM PET Computer and may be required when using devices originally designed for that Computer 3 1 4 End of String Characters for Output When data is sent to a device delimiting characters may be required Consult the manufacturer s manual to determine the delimiting character or characters that the device requires When data is output in modes 0 or 3 one or two end of string characters are appended The interface software defaults to two end of string characters CR carriage return ASCII code 13 and LF line feed ASCII code 10 To redefine the end of string characters as LF CR PROCeos_out_2chr 10 13 or status FNXeos_out_2chr 10 13 or to define a single end of string character as LF PROCeos_out_lichr 10 or status FNXeos_out_lchr 10 3 1 5 End of String Characters for Input When data is received from a device delimiting characters may be sent Consult the manufacturer s manual to determine t
38. tputs the string HLTLFM 77455 1 in mode 0 ie the default end of string characters CR carriage return and LF line feed are appended The string halts HLT the analyser and prepares it to list from its memory LFM the 16 bit switch register word that describes its display state Line 1110 addresses device 11 the analyser to talk and inputs two bytes of data in mode 2 and stores it in memory starting at address displaystate Line 1120 addresses device 11 the analyser to listen and outputs the string LFM 74000 512 in mode 0 The string prepares the analyser to list from its memory LFM the 512 16 bit words of its display buffer Line 1130 addresses device 11 the analyser to talk and inputs 1024 bytes of data in mode 2 and stores it in memory starting at address display Line 3000 addresses device 11 the analyser to listen and outputs the string HLTWTM 77455 1 in mode 0 The string halts HLT the analyser and prepares to write to its memory WTM the 16 bit switch register word that describes its display state Line 3010 addresses device 11 the analyser to listen and outputs the two bytes of data from memory starting at address displaystate in mode 2 Line 3020 addresses device 11 the analyser to listen and outputs the string WTM 74000 512 in mode 0 The string prepares the analyser to write to its memory WTM the 512 16 bit words Line 3030 addresses device 11 the analyser to listen and outputs 1024 bytes of data in mode 2 a

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