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THE BBC MICROCOMPUTER IEEE488 INTERFACE USER GUIDE

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1. o o a lel poll response byte 0 Or PLPOOOOOOOP ralle 000 000 000 000 001 010 1 00 000 DOO OO Bit 3 of the integer specifies the sense of the response Refer to the manufacturer s manual to decide on its setting During a parallel poll request each enabled device compares its individual status with the value of the sense bit it received when it was enabled If the comparison succeeds the bit assigned to that device is set in the parallel poll response byte If a device is no longer required to take part in a parallel poll the PARALLEL POLL DISABLE command is used The PARALLEL POLL UNCONFIGURE command renders all devices unable to take part in a parallel poll Example 640 siggenS OPENIN 5 650 counter S OPENIN 6 660 analyser S OPENIN IO 670 PRINT cmd PARALLEL POLL UNCONFIGURE REM to ensure no other devices tak part in parallel poll 680 PRINT cmd PARALLEL POLL ENABLE siggen 8 REM sense bit 1 ppr bit 690 PRINT cmd PARALLEL POLL ENABLE counter 9 REM sense bit 1 ppr bit 1 700 PRINT cmd PARALLEL POLL ENABLE analyser 2 REM sense bit 0 ppr bit 2 710 PRINT cmd PARALLEL POL
2. 100 PRINT cmd DEVICE CLEAR IEEE Status Required before Execution The computer is controller in charge flag must be set TRANSFER in progress flag must be unset CLEAR command executed flag must be set conflict for control of interface flag must be unset computer in process of acknowledging an unidentified command from another device flag must be unset IEEE Status after Execution No change Remote Messages ATN true DCL Description After this command has been executed all devices with a device clear capability are initialised Associated Commands SELECTED DEVICE CLEAR DO END OF STRING Purpose To specify the characters delimiting device dependent messages Example 100 endchr CHRS 13 CHR S 10 110 PRINT cmd END OF STRING endchr Notes String constants and variables of 1 or 2 characters may be used to specify the end of string characters The default character is LF line feed IEEE Status Required before Execution No requirement IEEE Status after Execution No change Remote Messages None Description The computer stores the End of String characters and sends them after each string of data bytes it outputs and expects to receive them after each string of data bytes it inputs 30 GO TO LOCAL Purpose To return the referenced devices to local control Example 100 voltmeter OPENIN 9 110 plotter S OPENIN 5 120 PRINT cmd GO TO LOCAL voltm
3. 750 NEXT 15 760 RINT cmd UNTALK 770 5 TRANSFER Command If it is required to exchange ASCII or binary coded data between devices without storing it in the memory of the computer the TRANSFER command can be used Two options are available a TRANSFER with a count Example To print ten successive readings from a digital voltmeter primary address 3 on an IEEE488 printer primary address 9 The voltmeter sends the readings in the format N NNN CR LF ie 8 bytes per reading giving a count of 80 bytes 540 printer s OPENIN 9 550 voltmeter OPENIN 3 560 PRINT cmd LISTEN printer EXECUTE 570 PRINT cmd TALK voltmeter 580 PRINTfcmd 5 TRANSFER 80 590 PRINT cmd UNTALK 600 PRINT cmd UNLISTEN C 610 OSE voltmeter 620 OSE printer 11 b TRANSFER without a count This can only be used when the END message is sent with the last data byte to be exchanged It has the advantage of leaving the computer free to continue with other asks Example To send a wave form stored in the memory of a fast data capture unit primary address 5 to the memory of a spectrum analyser primary address 8 for analysis 460 analyser GPENIN 8 470 captureunit OPENIN 5 480 PRINT cmd LISTEN captureunit E
4. cnt3 cnt2 b2 ch2 ch2 ch2 cntl ch2 bn bi enti ch2 cntl ch1 ch1 ch1 cnt0 chil bl bo ento chil cnt0 8 HARDWARE The interface uses the Texas Instruments TMS 9914A GPIB Adapter together with the SN75160A and SN75162A octal GPIB transceivers The TMS 99144 interfaces the computer via the IMHZ bus to the IEEE488 bus It relieves the computer s processor of the task of handling IEEE488 protocol when commands and data are sent and received The TMS 9914A generates interrupts and so the processor does not have to spend time polling it As supplied the hardware is configured as system controller Molex link SI on interface PCB in position A and with the IEEE488 data bus to be driven by open collector outputs Molex link 52 on interface PCB in position C A 5 MHz crystal provides a clock for timing The TMS 9914A is connected to the IMHZ bus in accordance with the guidelines given in Ref 2 The interface is supplied with four terminating resistor packs They should be removed if the interface is not to be the last device on the IMHZ bus The read and write registers of the interface are located at addresses amp FC20 to amp FC27 The user who wishes to program the TMS 9914A directly in order to configure the computer as a simple talker listener should obtain Ref 3 and change the Molex link SI on the interface PCB from position A to position B 64 REFERENCES Ref 1 Ref 2 Ref 3 IEE
5. 4 2 110 counter OPENIN 9 120 PRINT cmd LISTEN printers EXECUTE 130 PRINT cmd TALK counters 140 PRINT cmd TRANSFER 1024 150 PRINT cmd UNTALK 160 PRINT cmd UNLISTEN Example b 100 printer S OPENIN 4 2 110 counter OPENIN 9 120 PRINT cmd LISTEN printers EXECUTE 130 PRINT cmd TALK counters 140 PRINT cmd TRANSFER 150 190 REPEAT 200 PRINT cmd STATUS 210 INPUT cmd status488 220 UNTIL status488 AND 8 8 Notes Integer constants and variables in the range to amp 7FFFFFF may be used for the number of data bytes to be transferred IEEE Status Required before Execution The computer is controller in charge flag must be set TRANSFER in progress flag must be unset CLEAR command executed flag must be set a device has been TALKed flag must be set a device or devices have been LISTENed flag must be set 53 conflict for control of interface flag must be unset controller in process of acknowledging an unidentified command from another device flag must be unset IEEE Status after Execution When the number of data bytes is specified as 1 to 134217727 example a the END end remote message received flag is set if this occurs during the TRANSFER When the number of data bytes is specified as 0 example b the TRANSFER
6. DEVICE CLEAR 44 SERIAL POLL Purpose To conduct a serial poll of the referenced device Example 100 logicanalyser OPENIN 7 110 PRINT cmd SERIAL POLL Iogicanalyser 1 120 INPUT cmd statusmessage Notes Integer constants and variables in the range 1 to 255 may be used for the number of status bytes sent by the device to be polled The status bytes may only be returned to a string variable via the command channel IEEE Status Required before Execution The computer is controller in charge flag must be set TRANSFER in progress flag must be unset CLEAR command executed flag must be set conflict for control of interface flag must be unset controller in process of acknowledging an unidentified command from another device flag must be unset IEEE Status after Execution If the RQS request service remote message is received the SRQ service request remote message received flag is reset The device has been TALKed flag is reset The device or devices have been LISTENed flag is reset Remote Messages ATN true UNL true SPE true MTA true MSA if specified false STB1 and RQS false STB2 etc false STBn true SPD true UNT 45 Description Following the receipt of an SRQ service request remote message the SERIAL Poll command should be used to determine which device requires service Associated Commands STATUS 46 STATUS Purpose To return information on the current state of th
7. Chapter 43 of the BBC Microcomputer User Guide However it should be noted that IEEEFS files are not true files in that they have no storage capability and serve only to pass information to the IEEFS OSFIND Opens a file for reading and writing The routine is entered at amp FFCE which indirects through amp 21C The value in A determines the type of operation A 800 causes a file or files to be closed A lt gt 800 causes a file to be opened IF A lt gt 0 then Y high byte and X low byte must contain the address of a location in memory which contains the file name terminated with CR MD On exit A will contain the channel number allocated to the file for all future operations If A 0 then the IEEEFS was unable to open the file If A 0 then a file or all files will be closed depending on the value of Y Y 0 will close all files otherwise the file whose channel number is in Y will be closed On exit C N V and Z are undefined and D O The interrupt state is preserved 60 OSBPUT This call is used to send data It write puts a byte in A to the file previously opened using OSFIND The routine is entered at amp FFD4 which indirects through amp 218 On entry Y contains the channel number allocated by OSFIND On exit A X and Y are preserved N V and Z are undefined and 020 The interrupt state is preserved OSBGET This call is used to receive data It gets reads a byte from a file into A The file must have be
8. secondary address 100 dvms OPENIN 4 A sixteen input analogue to digital converter has a primary address of 5 and a secondary address of 11 indicating the input to be converted 150 adc 0PENIN 5 11 If no channel is available a zero is returned All channels remain open even if other filing systems are selected until specifically closed while the IEEEFS is active A device channel be closed using the CLOSE statement Example 1110 CLOSE dvm The CLOSE 0 statement closes all device channels but not the COMMAND and DATA channels which must be closed individually As only 14 device channels may be open at one time it is recommended that channels are closed when no longer required or at the end of a program The BBC Microcomputer must also have a unique device address This is specified using the BBC DEVICE NO command and can be any number in the range 0 to 30 not already assigned to a device in the system Example To specify the primary address of the computer to 7 40 PRINT cmd BBC DEVICE NO 7 The CLEAR command is now used to initialise the system Example 50 PRINT cmd CLEAR The REMOTE ENABLE command is used to Prepare devices for remote operation eg under computer control Example 60 PRINT cmd REMOTE ENABLE Data strings of up to 255 characters When strings of ASCII coded data are sent to or received from a dev
9. sent using the OSBPUT and OSBGET calls strings are transferred as type amp 00 length and characters in reverse order When binary coded data is being handled it is sent and received a byte at a time Example Typical sequence of operating system calls Select IEEFFS by calling OSCII Open COMMAND and DATA channels by using OSFIND Execute IEEE commands eg CLEAR REMOTE ENABLE etc by calling OSWORD Open device channels by calling OSFIND Listen or talk devices by calling OSWORD Send and receive data by calling OSBPUT and OSBGET Close channels by calling OSFIND 25 0 Structure of OSWORD Block PARALLEL POLL DISABLE EL POLL ENABLE E LEL POLL REQUEST PARALLEL POLL UNCONFIGFURI U D 2 4 U o Gl O H UO H 02 D 0 1 mu o BPOOFPRFPOND OCOCRKROONDT OCD DS 5 Q pa Ooo coco ec CC OD OOOO OCOCOr OOO command amp 40 amp 50 amp 62 amp 81 amp 22 amp 20 amp 61 amp 21 amp 48 amp 02 amp 60 amp 14 amp 71 amp 70 amp 64 amp 24 amp 44 amp 01 amp 42 amp 41 amp 52 amp 51 amp 10 amp 28 amp 54 amp 58 amp 18 63 b 0 bl dev no eos2 eosl chn b chn m chn S ch1 ppr ppr cnt3 cnt2 chn E ch1 pllcnt b3 b2 chil chil cnt3 cnt2 chn
10. spectrumanaiyser EXECUTE APPENDIX 2 IEEEFS ERRORS Error number amp DC syntax amp 88 out of range amp DE channel amp 8A no device listened type mismatch amp 8B no BBC DEVICE NO 88D string too long 889 no device talked amp 8 CLEAR not executed amp FE Bad command APPENDIX 3 INTERFACE REMOTE MESSAGES List of Messages Referenced in this Guide Mnemonic ATN attention DAB data byte DCL device clear END end EOS end of string GET group execute trigger GTL go to local IDY identify IFC interface clear LLO local lockout MIA my listen address MTA my talk address MSA my secondary address PPC parallel poll configure PPE parallel poll enable PPD parallel poll disable PPR parallel poll response PPU parallel poll unconfigure REN remote enable RQS request service SDC selected device clear SPD serial poll disable SPE serial poll enable SRQ service request STB status byte TCT take control UNL unlisten UNT untalk APPNDIX 4 INTERFACE SPECIFICATION note 1 SH source handshake function SH1 complete capability AH acceptor handshake function AH1 complete capability T talker function note 2 TS complete capability L listener function note 2 L3 complete capability SR service request SR1 complete capability RL remote local function RLO no capability PP parallel poll function PPO no capability DC device clear function DCO no capability DT device trigger function DTO no capabil
11. the lower case and CAREFULLY unplug the 17 way ribbon cable connecting the keyboard assembly to the main Printed Circuit Board PCB by pulling the socket away from PLI3 on the main PCB Move the keyboard away from the main PCB until the loudspeaker plug is accessible Unplug the loudspeaker by CAREFULLY removing the socket from PLI5 Place the keyboard assembly to one side on a flat surface If your computer contains an operating system of version 1 00 or later proceed to instruction 9 The current Machine Operating System MOS is situated in the bottom right hand corner of the main PCB in one of two formats as follows One integrated circuit IC in socket 1C51 identified by the legend Bo2 1 printed on top If you have this format carefully remove the MOS IC from 1C51 using an IC extractor a small screwdriver used with extreme care will do Four ICs in sockets IC52 1C88 ICIOO and ICIOI these sockets are all next to each other despite the numbering identified with the legends C D E and F respectively printed on the top If this is the case the BASIC language IC identifiable by the legend BOI printed on the top and all four MOS ICs should be removed as described in a above Replace the BASIC IC in socket IC100 as described in 8 The new MOS is supplied In a single IC identified by the legend B04 printed on the top Insert the ROM carefully into the socket 1C51 ensuring that all the Tegs locate properly into the hol
12. 13 14 16 16 17 18 6 THE IEEE FILING SYSTEM A Summary Channels Device Addresses Device Dependent Messages Data Glossary of IEEEFS Commands 7 USING THE IEEE FILING SYSTEM IN ASSEMBLER 8 HARDWARE REFERENCES APPENDICES 1 IEEEFS Commands Minimum Abbreviations 2 IEEEFS Errors 3 Interface Remote Messages 4 Interface Specification 5 Fitting the IEEEFS EPROM 6 Removal of Terminating Resistor Packs INDEX INTRODUCTION Before using your IEEE488 interface check that you have received the following items in addition to this User Guide IEEE488 Interface IEEEFS EPROM Guarantee Card Delta Ribbon Cable for connecting one IEEE488 device to the computer If any item is missing contact the dealer who supplied the IEEE488 interface quoting the order number given to you when you placed your order It is strongly recommended that the IEEEFS EPROM be fitted by a dealer However fitting instructions are included in Appendix 5 and information on the use of the terminating resistors in the IEEE488 Interface are contained in Appendix 6 Connecting the Interface to the Computer 1 Turn off the power to the computer and the interface 2 Plug the 34 way IDC socket on the end of the ribbon cable into the IMHZ Bus header on the underside of the computer Ensure that pin 1 of the socket is aligned with pin 1 of the header The small indents on the socket should face the printed panel 3 Tur on the power to the interface an
13. 6 220 PRINT cmd TALK counter Note If there is already an active talker it will automatically be untalked Data is then received from the device via the DATA channel using the INPUT statement All active listeners will receive the data sent Example 230 INPUT data count When input has been completed the device can be untalked Example 580 PRINT cmd UNTALK Checking the State of the Interface The IEEEFS maintains a status word This is available to the user through the STATUS command The meaning of each bit of the status word is detailed in Chapter 6 under STATUS When ASCII coded data is being handled there are three status bits of interest bit4 if set indicates the input sequence was terminated because over 255 characters were received before the delimiting characters bit6 if set indicates the END message was received from a device with the last character bit 7 if set indicates an incomplete source handshake This is most likely to occur during a TALK or LISTEN sequence if no devices are connected to the interface Example 1030 PRINT cmd STATUS 1040 INPUT cmd states 1050 IF state AND 64 64 THEN PRINT END received ELSE PRINT NO END received An Example of Data Input and Output It is required to take three readings in the range 0 to 5v from a digital voltmeter with a primary address of 9 and print them on the computer s screen The voltmeter
14. E Std 488 1978 IEEE488 Standard Digital Interface for Programmable Instrumentation The Institute of Electrical and Electronic Engineers Inc 1978 Application Note No 1 BBC Microcomputer IMHZ Bus Acorn Computers ltd 1982 TMS 9914 GPIB Adapter Data Manual Texas Instruments APPENDIX 1 IEEE Commands BBC DEVICE NO CLEAR DEVICE CLEAR END OF STRING EXECUTE GO TO LOCAL LISTEN LOCAL LOCKOUT PARALLEL POLL DISABLE PARALLEL POLL ENABLE PARALLEL POLL REQUEST PARALLEL POLL UNCONFIGURE READ BINARY REMOTE DISABLE REMOTE ENABLE REQUEST CONTROL SELECTED DEVICE CLEAR SERIAL POLL STATUS TAKE CONTROL TALK TIMEOUT OFF TIMEOUT ON TRANSFER TRIGGER UNLISTEN UNTALK WRITE BINARY Minimum Abbreviation QMmMm OO L LO PARALLEL POLL D PARALLEL POLL E P PARALLEL POLL U R REMOTE D REM REQ SEL SE S TAK T TIMEOUT OFF TI TR TRI UNI U W Note Standard IEEE488 mnemonics can be used as string variable names Example ri z 3 100 PPUS PARAL POLL UNCONFIGURE 110 PPES PARAL POLL ENABLE 120 PPR PARALLEL POLL REQUEST 130 5 POLL DISABLE r ri 650 spectrumanalyser OPENIN 9 660 PRINT cmd PPUS 670 PRINT cmd PPES spectrumanalyser 10 940 PRINT cmd PPR 950 INPUT cmd responses 990 PRINT cmd PPDS
15. EAR command to return all devices with the capability to a Known state Example 410 voltmeter OPENIN 6 530 PRINT cmd SEL ECT ED D EVICE FEAR voltmeters voltmeter to known condition Xi EXECUTE EM return 790 PRINTfcmd DEVICE CLEAR REM returns all devices with the capability to a known condition Triggering Simultaneous Operation of Devices Sometimes for example in test systems it may be required to start a process and commence measurements at the same time This can be achieved using the TRIGGER command which sends the GET group execute trigger message Example 660 signalgenerator OPENIN IO 670 recorder OPENIN 9 930 PRINT cmd TRIGGER Signalgenerator recorder EXECUTE REM start measurement process 18 5 PASSING CONTROL The system controller is the device which can send the IFC interface clear and REN remote enable messages and only one is allowed in a system The IEEEFS and the interface hardware is supplied configured so that the computer acts as system controller The controller in charge is the device which manages the system This is not necessarily the system controller After the CLEAR command has been executed the computer is controller in charge The TAKE CONTROL command can be used to pass management of the system to another devic
16. L 845 PARALLEL POLL DISABLE Purpose To disable the referenced devices so that they are unable to take part in a parallel pall Example 100 analyser S OPENIN 11 110 voltmeter OPENIN 6 120 PRINT cmd PARALLEL POLL DISABLE analyser voltmeter EXECUTE Notes The last channel must be followed by the EXECUTE command IEEE Status Required before Execution The computer is controller in charge flag must be set TRANSFER in progress flag must be unset CLEAR command executed flag must be set conflict for control of interface flag must be unset computer in process of acknowledging an unidentified command from another device flag must be unset IEEE Status after Execution The device or devices have been LISTENed flag is reset Remote Messages ATN true UNL true MLA 1 true MSA 1 if specified true MLA 2 true MSA 2 if specified etc true MLAn true MSAn if specified true PPC true PPD true UNL Associated Commands PARALLEL POLL ENABLE PARALLEL POLL UNCONFIGURE PARALLEL POLL REQUEST 35 PARALLEL POLL ENABLE Purpose To enable the referenced device to take part in a parallel poll Example 100 spectrumanalyser OF 110 PRINTVPcmd PARALLEL Notes POLL ENIN 9 ENABL E spectrumanalyser 10 The parallel poll response remote message is specified by the least significant 4 bits of an integer co
17. L REQUEST 720 INPUT cmd responsebyte 730 IF responsebyte AND 1 1 THEN PROCservicesiggen 740 IF responsebyte AND 2 2 THEN PROCservicecounter 750 IF responsebyte AND 4 4 THEN PROCserviceanalyser 1020 PRINT cmd PARALLEL POLL DISABLE analyser EXECUTE REM analyser no longer required to take part in parallel poll 15 4 OTHER COMMANDS The Timeout Facility The TIMEOUT ON command can be used to enable a 2 5 sec timeout This is useful in preventing a program from hanging up when a device fails to respond Bit 0 in the status word is set if a timeout occurs during output and bit 1 is set if a timeout occurs during input If timeouts are no longer required the TIMEOUT OFF command is used Timeouts are not part of the IEEE488 standard and so the IEEEFS defaults to TIMEOUT OFF Example 500 510 520 530 540 550 560 RINT cmd TIMEOUT ON dc OPENIN 17 3 RINT cmd TALK adc NPUT cmd reading RINT cmd STATUS NPUT cmd state F states AND 2 2 THEN PROCtimeoutoninput HH UH 0 tU 730 PRINT cmd TIMEOUT OFF Remote Local Operation When a device is listened after a REMOTE ENABLE command control of the device passes from its front panel to the computer The LOCAL LOCKOUT command prevents devices with this capability from inadvertently being returned to front panel control If it is wis
18. N or OPENOUT functions are used to pass the primary and secondary if specified addresses of a device to the IEEEFS via a device channel Addresses must be in the range 0 30 Note that the primary address of the BBC Microcomputer is specified by the BBC DEVICE NO command Example A voltmeter has a primary address of 4 and a secondary address of 2 100 voltmeter S OPENIN 4 2 An analyser has a primary address of 11 100 analyser S OPENIN 11 A device channel may be closed using the CLOSE statement Example 100 CLOSEfvoltmeterS 100 CLOSE 0 closes all device channels but not the COMMAND and DATA channels which must be individually closed Device Dependent Remote Messages Data Strings Input Strings of up to 255 characters can be input by the IEEEFS and passed to the language via the DATA channel The INPUT statement is used The IEEEFS expects to receive the end of string characters after each string input from device However if the END end remote message is received before the end of string characters this terminates the input sequence 22 Remote Messages ATN true computer addresses itself as a listener false DAB 1 false DAB 2 etc false DABn false EOS 1 end of string false EOS 2 and END characters true computer unaddresses itself as a listener Example 100 PRINT cmd END OF STRING CHRS 13 CHR S 10 110 PRINT cmd TALK analyser 120 INPUT dat
19. THE BBC MICROCOMPUTER IEEE488 INTERFACE USER GUIDE THE BBC MICROCOMPUTER IEEE488 INTERFACE USER GUIDE Designed developed and manufactured in the United Kingdom by Acorn Computers Ltd and Intelligent Interfaces Ltd written by Andrew G Ray Intelligent Interfaces Ltd January 1983 C Copyright Acorn Computers Limited and Intelligent Interfaces Limited 1983 Neither the whole or any part of the information contained in or the product described in this manual may be adapted or reproduced in any material form except with the prior written approval of Acorn Computers Limited Acorn Computers and Intelligent Interfaces Limited Il The product described in this manual and products for use with it are subject to continuous development and improvement All information of a technical nature and particulars of the product and its use including the information and particulars in this manual are given by Acorn Computers and II in good faith However it is acknowledged that there may be errors or omissions in this manual A list of details of amendments or revisions to this manual can be obtained upon request from Acorn Computers Technical Enquiries Acorn Computers welcome comments and suggestions relating to the product and this manual All correspondence should be addressed to Technical Enquiries Acorn Computers Ltd Fulbourn Road Cherry Hinton Cambridge CBI 4JN All maintenance and service on the product must be carried out by Ac
20. XECUTE 490 PRINT data OUT 3000 1024 REM prepare capture unit to output data 500 PRINT cmd UNLISTEN 510 PRINT cmd3 LISTEN analyser EXECUTE 520 PRINT data WIM 2000 1024 REM prepare analyser in input data 530 PRINT cmd TALK captureunits 540 RINT cmd TRANSFER 0 REM transfer with no count REM computer continuing with other tasks 910 REPEAT REM read the status word until the END message is received 920 PRINT cmd STATUS REM causing the transfer in progress flag to be reset I U 930 INPUT cmd states 940 UNTIL state AND 8 8 12 3 HOW TO FIND OUT WHAT A DEVICE IS DOING Serial Poll If a device requires action from the computer for example in order to rectify some error condition it requests this by sending the SRQ service request message When this happens bit 5 of the status word is set The SERIAL POLL command is used to determine which device has requested service Each device with a serial poll capability must be polled Consult the manufacturer s manual for each device to find out how many bytes it returns Most devices return a single byte Bit 6 of the first byte returned conveys the RQS request service message If set this indicates that the device was requesting service The remaining bits of the first byte and ensuing bytes if any indicate the reason that service was requested T
21. a response Strings Output Strings of up to 255 characters passed to the IEEEFS via the DATA channel can be output The PRINT statement is used The IEEEFS sends the UNT untalk remote message before the string and the end of string characters after each string it outputs to a device It sends the END end remote message with the last character Remote messages ATN true UNT computer addresses itself as a talker false DAB 1 false DAB 2 etc false DABn false EOS 1 end of string false EOS 2 and END characters true computer unaddresses itself as a talker Example 100 PRINT cmd END OF STRING CHRS 13 CHR S 10 110 PRINT cmd LISTEN analyser EXECUTE 120 PRINT data AV4 RE 23 Binary Coded Data If this is to be handled the READ BINARY and WRITE BINARY commands are used Single data bytes are passed to and from the language via the DATA channel The BPUT and BGET statements are used For further details see the READ BINARY and WRITE BINARY commands 24 IEEEFS Commands The following pages describe the IEEE commands under a number of headings Purpose A plain English description of what the command does Example An example to illustrate the use of the command Notes Lists restraints regarding type and range of variables IEEE Status Required before Execution Lists the status flags checked by the IEEEFS before carrying out a command IEEE S
22. ard 1 IEEE 3 21 IEEEFS 3 60 INPUT 7 LISTEN 6 33 LOCAL LOCKOUT 16 17 34 OPENIN 5 OPENOUT 5 OSARGS 61 OSBGET 61 OSBPUT 61 OSCIl 62 OSFIND 60 OSWORD 61 63 PARALLEL POLL 14 DISABLE 14 15 35 ENABLE 14 15 36 REQUEST 14 15 37 UNCONFIGURE 14 15 38 Primary address 4 22 PRINT 7 READ BINARY 10 11 39 REMOTE DISABLE 16 17 41 REMOTE ENABLE 6 16 42 REQUEST CONTROL 19 43 Secondary address 4 22 SELECTED DEVICE CLEAR 17 44 SERIAL POLL 13 45 Source handshake 8 STATUS 8 47 48 System controller 19 TAKE CONTROL 19 45 TALK 7 50 Terminating resistors Appendix 6 TIMEOUT OFF 16 51 TIMEOUT ON 16 52 TRANSFER 11 12 53 54 TRIGGER 18 55 UNLISTEN 7 56 UNTALK 7 57 WRITE BINARY 10 58 59 ACORN CONPUTERS LTD Fulbourn Road Cherry Hinton Cambridge CB 1 4
23. bytes sent false DAB 2 etc false DAB n and END true 58 Description This command enables the output of long over 255 data bytes binary coded device dependent messages The computer flags binary coded data is being handled in the IEEE status word and after sending the UNT untalk remote message addresses itself as a talker A single data byte is output in response to each BPUT The END end remote message is sent with the last data byte When the specified number of data bytes have been output the computer resets the flag in the IEEE status word and unaddresses itself as a talker Associated Commands LISTEN UNLISTEN 59 7 USING THE IEEE FILING SYSTEM IN ASSEMBLER Read Chapter 43 of the BBC Microcomputer User Guide before writing assembler programs that use the IEEE488 interface General information on using a filing system in assembler is presented there This chapter gives details of the relevant operating system calls when using the IEEEFS OSFIND amp FFCE Open or close a channel OSGBPB 8 1 Not supported by IEEEFS OSBPUT amp FFD4 Send a single byte to channel from A OSBGET amp FFD7 Receive a single byte from channel in A OSARGS amp FFDA Not fully supported by IEEEFS OSFILE amp FFDD Not supported by IEEEFS OSWORD amp FFF1 Perform IEEE commands using parameter block to pass parameters OSCLI amp FFF7 Interpret IEEEFS command line Throughout this section the term file is used to maintain compatibility with
24. cts a serial poll the STB status byte and RQS request service remote messages are sent The seven bits of the STB remote message are all 0 If the controller in charge sends the TCT take control remote message the computer becomes controller in charge and sets the appropriate flag in the IEEE status word Associated Commands TAKE CONTROL CLEAR AD SELECTED DEVICE CLEAR Purpose To clear the referenced devices Example 100 plotter S OPENIN 7 110 counter OPENIN 3 120 PRINT cmd SELECTED DEVICE CLEAR plotter counter EXECUTE Notes The last channel must be followed by the EXECUTE command IEEE Status Required before Execution The computer is controller in charge flag must be set TRANSFER in progress flag must be unset CLEAR command executed flag must be set conflict for control of interface flag must be unset computer in process of acknowledging an unidentified command from another device flag must be unset IEEE Status after Execution The device or devices have been LISTENed flag is reset Remote Messages ATN true UNL true MLA 1 true MSA 1 if specified true MLA 2 true MSA 2 if specified etc true MLAn true MSAn if specified true SDC true UNL Description After this command has been executed the devices with the device clear capability referenced by the previously OPENINed channels are initialised Associated Commands
25. cution The computer is controller in charge flag must be set TRANSFER in progress flag must be unset CLEAR command executed flag must be set conflict for control of interface flag must be unset computer in process of acknowledging an unidentified command from another device flag must be unset IEEE Status after Execution The computer is controller in charge flag is reset device or devices have been LISTENed flag is reset device has been TALKed flag is reset Remote Messages ATN true UNL true MTA true MSA if specified true TCT false Description After this command has been executed the computer may regain control of the interface through REQUEST CONTROL or CLEAR commands Associated Commands REQUEST CONTROL CLEAR dg TALK Purpose To address the referenced device as a talker Example 100 digitalvoltmeter OPENIN 2 1 110 PRINT cmd TALK digitalvoltmeter Notes Only one device may be TALKed at any one time IEEE Status Required before Execution The computer is controller in charge flag must be set TRANSFER in progress flag must be unset CLEAR command executed flag must be set conflict for control of interface flag must be unset controller in process of acknowledging an unidentified command from another device flag must be unset IEEE Status after Execution The device has been TALKed flag is set Remote Messages ATN true MTA true MSA if specified Description The com
26. d computer The IEEE488 Standard The IEEE488 interface is a general purpose system for exchanging digital data bit parallel byte serial form between a number of devices 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 The interface is identical to that described in the IEC International Electrotechnical Commission Publication 625 1 apart from the mechanical connection system The IEEE standard specifies a 24 pin Microribbon connector whereas the IEC Publication specifies a 25 pin D type connector as used for the EIA R5232 C data communication interface The IEEE499 interface makes use of two types of messages i interface messages commands used to manage the interface ii device dependent messages data 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 or manage the system act as a controller This User Guide does not attempt to reproduce the IEEE 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 BBC Microcomputer and IEEE488 Interface with any other IEEE488 device Information covered and where to find it in thi
27. e Example To pass control to another computer with an IEEE488 interface primary address 13 340 secondcontroller S OPENIN 13 350 PRINT cmd TAKE CONTROL secondcontroller After control has been passed to another device there are three ways in which the computer can regain management of the system i i When the current controller in charge addresses the computer and sends the TCT take control message The REQUEST CONTROL command can be used to indicate to the current controller in charge that the BBC Microcomputer wishes to regain control of the system It does this by sending the SRQ service request message and when polled by the current controller in charge during a serial poll sends the RQS message indicating it was requesting service together with a STB status byte of zero showing it wishes to regain control There is no obligation on the current controller in charge to pass back control to the BBC Microcomputer However if it does this occurs as described in the previous paragraph To find out when the computer has regained control bit 2 of the status word should be checked 19 Example 870 PR INT Cmd REQUEST CONTROL 880 REPEAT 890 PRINT cmd STATUS 900 INPUT cmd states 910 UNTIL state AND 4 4 ili through the use of the CLEAR command the BBC Microcomputer sends the IFC interface clear message This instantly halts any current activi
28. e interface Example 100 PRINT cmd STATUS 120 INPUT cmd state Notes The status may only be returned to an integer variable via the command channel IEEE Status Required before Execution No requirement IEEE Status after Execution No change Remote Messages None Description The individual bits of the status word indicate the following 47 w NOOR OT O timeout on output timeout on input computer is controller in charge TRANSFER in progress string of more than 255 characters received SRQ service request remote message received END end remote message received Incomplete source handshake binary coded data being handled TIMEOUT ON COMMAND file open DATA file open a device has been TALKed a device or devices have been LISTENed BBC DEVICE NO executed CLEAR executed input error output error conflict for control of interface computer in process of becoming controller in charge computer in process of acknowledging an unidentified command from another device computer in process of entering the controller active state following a TRANSFER command unused REN remote enable remote message being sent unused unused unused unused unused unused unused non fatal error 48 TAKE CONTROL Purpose To pass control to another device Example 100 secondcontroller OPENIN 2 110 PRINT cmd TAKE CONTROL secondcontroller IEEE Status Required before Exe
29. e set conflict for control of interface flag must be unset computer in process of acknowledging an unidentified command from another device flag must be unset IEEE Status after Execution The device or devices have been LISTENed flag is reset Remote Messages ATN true UNL true MLA 1 true MSA 1 if specified true MLA 2 true MSA 2 If specified etc true MLAn true MSAn if specified true GET true UNL Description This command causes all devices with the device trigger capability referenced by the previously OPENINed channels to start some basic operation Associated Commands None 55 UNLISTEN Purpose To unaddress all active listeners Example 100 PRINT cmd UNLISTEN IEEE Status Required before Execution The computer is controller in charge flag must be set TRANSFER in progress flag must be unset CLEAR command executed flag must be set conflict for control of interface flag must be unset controller in process of acknowledging an unidentified command from another device flag must be unset IEEE Status after Execution The device or devices have been LISTENed flag is reset Remote Messages ATN true UNL Description The computer sends the UNL unlisten remote message to all active listeners Associated Commands LISTEN 56 UNTALK Purpose To unaddress an active talker Example 100 PRINT cmd UNTALK IEEE Status Required before Execution The computer is controller in c
30. e unset computer in process of acknowledging an unidentified command from another device flag must be unset IEEE Status after Execution The binary coded data being handled flag is set Remote Messages ATN false DAB 1 data bytes received false DAB 2 etc false DABn and END the END remote message is not required true Description This command enables the input of long in excess of 255 data bytes binary coded device dependent remote messages The computer flags binary coded data being handled in the IEEE status word and addresses itself as a listener A single data byte is input in response to each BGET When the specified number of data bytes have been input the computer resets the flag in the IEEE status word and unaddresses itself as a listener If the END end remote message is received during a READ BINARY command this is flagged in the IEEE status word However it does not terminate the input Associated Commands TALK UNTALK 40 REMOTE DISABLE Purpose To return all devices to local control Example 100 PRINTicmd REMOTE DISABLE IEEE Status Required before Execution The CLEAR command executed flag must be set IEEE Status after Execution The REN remote enable remote message being sent flag is reset Remote Messages REN false Description After this command has been executed all devices with a remote local capability are returned to local control including those put in
31. en previously opened using OSFIND and the channel number allocated must be in V The routine is entered at amp FFO7 which indirects through amp 216 On exit C 0 indicates a valid character in A X and Y are preserved N V and Z are undefined and 0 0 The interrupt state is preserved OSARGS This routine is entered at amp FFDA and indirects through amp 214 The IEEEFS only supports a call with A amp 0 and Y amp 0 this returns with A U7 indicating that the IEEEFS is in use On exit X and Y are preserved C N V and Z are undefined and D O The interrupt state is preserved OSWORD This routine is entered at amp FFFI and indirects through amp 20C IEEE commands are sent and information on the state of the interface received through the use of a single OSWORD call with A amp 80 This fulfils the same function as the COMMAND channel Y high byte and X low byte point to a parameter block The structure of this is first byte no of bytes in argument second byte no of bytes in result third byte command code subsequent bytes as defined by the first three bytes 61 Details of each command are given in the table OSCLI This call is used to select the IEEEFS by placing the address of the command line IEEE in V high byte and X low byte and calling amp FFF7 which indirects through amp 2M The command line should not start with an asterisk and must end with amp OD Any leading spaces will be stripped DATA When data is
32. er IEEE488 dealer In the event of the fuse blowing it must be replaced after clearing any faults with a 3 Ampere fuse that is ASTA approved to BS1362 As the colours of the wires may not correspond with the coloured markings identifying the terminals in your plug proceed as follows The wire which is coloured green and yellow must be connected to the terminal in the plug which is marked by the letter E or by the safety symbol or coloured green or green and yellow The wire which is coloured blue must be connected to the terminal which is marked with the letter N or coloured black The wire which is coloured brown must be connected to the terminal which is marked with the letter L or coloured red Not necessarily the same shade of that colour CONTENTS INTRODUCTION Connecting the Interface to the Computer The IEEE488 Standard Information Covered and Where to Find It in this User Guide 1 GETTING GOING Simple Data Transfer The IEEE Filing System Data strings of up to 255 characters Data Output Data Input Checking the State of the Interface An Example of Data Input and Output 2 MORE ON DATA TRANSFER Binary Coded Data The TRANSFER Command 3 HOW TO FIND OUT WHAT A DEVICE IS DOING Serial Poll Parallel Poll 4 OTHER COMMANDS The Timeout Facility Remote Local Operation Initialising Devices Triggering Simultaneous Operation of Devices 5 PASSING CONTROL 0 NA CO WW 10 11
33. es and are not bent under upon insertion The IC should be orientated so that the semi circular cutout in the top of the IC is at the top i e away from the keyboard Avoid touching the IC legs with your fingers wherever possible Now set the following links 518 North 519 East 20 North 521 Two off East West S22 North S32 West S33 West N B North is the edge of the PCB nearest to the back of the case and South is the edge nearest to the keyboard East and West follow logically from these Insert the IEEEFS EPROM IC into any free socket IC88 ICIOO or ICIOI as described in 8 If you have a disc filing system DFS ensure that the IEEEFS EPROM is inserted to the right of the DFS IC Reassemble the BBC Microcomputer by reversing instructions 2 to 5 To check that the IEEEFS EPROM has been fitted correctly type HELP IEEE The computer should display IEEE Filing System lt version number gt O S lt version number gt If it does not disconnect the computer from the mains supply and ensure that all the instructions have been followed correctly Reconnect to the supply and try again If you still have problems contact an authorised dealer APPENDIX 6 REMOVAL OF TERMINATING RESISTOR PACKS The interface is supplied with four terminating resistor packs They should be removed following the instructions below if the interface is not to be the last device on the IMHZ bus 1 Switch off the interface and disconnect it f
34. es of binary coded data The last byte Is normally accompanied by the END end remote message Data of this type can be sent and received using the WRITE BINARY and READ BINARY commands together with the BPUT and BGET statements Example To send 1024 data bytes held in an array to the memory of a spectrum analyser primary address 11 870 analyser S OPENIN 11 880 PRINT cmd LISTEN analyser EXECUTE 890 PRINT data WIM 4000 1024 REM prepare analyser to receive data and store it in memory starting at location amp 4000 900 PRINT cmd WRITE BINARY 1024 REM send the next 1024 bytes and accompany the last byte with the END message 910 FOR I 1 TO 1024 920 BPUT data waves 15 REM output byte 930 NEXT I 940 PRINT cmd UNLISTEN 950 5 Q WU Z WH Example To receive 512 data bytes from the memory of a digital storage oscilloscope primary address 15 and store them in an array 670 scope 0PENIN 15 680 PRINT cmd LISTEN scope EXECUTE 10 690 RINT data CHI REM prepare oscilloscope to send data 700 PRINT cmd UNLISTEN 710 PRINT cmd TALK scope 720 PRINT Hcmd READ BINARY 512 REM prepare to receive 512 bytes P P P P 730 FOR I 1 TO 512 740 BGET data trace I REM input byte N P C
35. eter plotter EXECUTE Notes The last channel must be followed by the EXECUTE command IEEE Status Required before Execution The computer is controller in charge flag must be set TRANSFER in progress flag must be unset CLEAR command executed flag must be set conflict for control of interface flag must be unset computer in process of acknowledging an unidentified command from another device flag must be unset IEEE Status after Execution The device or devices have been LISTENed flag is reset Remote Messages ATN true UNIL true MLA 1 true MSA 1 if specified true MLA 2 true MSA 2 if specified etc true MLAn true MSA n if specified true GTL true UNL o Description After this command has been executed devices with a remote capability referenced by the previously OPENINed channels are returned to local control Associated Commands REMOTE ENABLE REMOTE DISABLE LISTEN LOCAL LOCKOUT a LISTEN Purpose To address the referenced devices as listeners Example 100 voltmeterS 0PENIN 2 1 110 printer S OPENIN 5 120 PRINT cmd LISTEN voltmeter printer EXECUTE Notes Up to 14 devices may be LISTENed at any one time The last channel must be followed by the EXECUTE command IEEE Status Required before Execution The computer is controller in charge flag must be set TRANSFER in progress flag must be unset CLEAR co
36. executed flag must be set IEEE Status after Execution The timeout on output flag is reset timeout on input flag is reset computer is controller in charge flag is set TRANSFER in progress flag is reset string of more than 255 characters received flag is reset SRQ service request remote message received flag is reset END end remote message received flag is reset incomplete source handshake flag is reset binary coded data being handled flag is reset a device has been TALKed flag is reset a device has been LISTENed flag is reset CLEAR command executed flag is set input error flag is reset output error flag is reset conflict for control of interface flag is reset computer in process of becoming controller in charge flag is reset computer in process of acknowledging an unidentified command from another device flag is reset computer in process of entering the controller active state following a TRANSFER command flag is reset REN remote enable remote message being sent flag is reset non fatal error flag is reset Remote Messages IFC IFC false 27 Description The primary address of the computer as specified by the BBC DEVICE NO command is set before sending the IFC interface clear remote message This places the interface in a known quiescent state The computer exits the command as controller in charge Associated Commands BBC DEVICE NO 0 DEV1CE CLEAR Purpose To clear all devices Example
37. harge flag must be set TRANSFER in progress flag must be unset CLEAR command executed flag must be set conflict for control of interface flag must be unset controller in process of acknowledging an unidentified command from another device flag must be unset IEEE Status after Execution The device has been TALKed flag is reset Remote Messages ATN true UNT Description The computer sends the UNT untalk remote message to the active talker Associated Commands TALK 57 WRITE BINARY Purpose To enable the output of a specified number of data bytes Example 100 analyser S OPENIN 11 PRINT cmd LISTEN analyser EXECUTE PRINT cmd WRITE BINARY 1024 FOR 1 1 TO 1024 140 BPUT data t waveforms 1 N EXT OSE analyser Notes Integer constants and variables in the range 1 to amp 7FFFFFF may be used for the number of data bytes IEEE Status Required before Execution The computer is controller in charge flag must be set TRANSFER in progress flag must be unset a device or devices have been LISTENed flag must be set CLEAR command executed flag must be set conflict for control of interface flag must be unset computer in process of acknowledging unidentified command from another device flag must be unset IEEE Status after Execution The binary coded data being handled flag is set Remote Messages ATN true UNT false DAB 1 data
38. he meaning of this information can be found in the manufacturer s manual and the appropriate action should be taken Example 270 PRINT cmd STATUS 280 INPUT cmd states 290 IF states AND 32 32 THEN GOTO 5000 5000 counter OPENIN 6 5010 signalgenerator OPENIN 13 5020 PRINT cmd SERIAL POLL counter 1 REM 1 byte expected 5030 INPUT cmd counterstatus 5040 IF ASC counterstatus AND 64 64 THEN PROCservicecounter 5050 PRINT cmd SERIAL POLL signalgenerator 1 5060 INPUT cmd signalgeneratorstatus 5070 IF ASC signalgeneratorstatus AND64 64 THEN PROCservicesignalgenerator Because each device must be polled separately a serial poll is time consuming 13 Parallel Pall This is a rapid way of finding out whether one or more devices require action by the computer However the computer must be committed to carrying out a parallel poll periodically The PARALLEL POLL REQUEST command returns a single parallel poll response byte each bit of which is assigned to a device or devices and if set indicates that the device requires action by the computer Devices with a parallel poll capability are assigned a bit in the parallel poll response byte using the PARALLEL POLL ENABLE command This command uses an integer the least significant 3 bits of which specify the associated bit of the parallel poll response byte as follows b
39. hed to return control to the front panel the GO TO LOCAL command is used However when the device is next listened the front panel switches will again be locked out To disable the locking out of the switches the REMOTE DISABLE command should be used This also has the effect of returning all devices to local control 16 Example 110 PRINT cmd REMO TE ENABLE 120 voltmeter5 OPENIN 21 140 PRINT cmd LIST 130 PRINT cmd LOCAL front panel switches i neff ctiv 150 PRINTfdatas R2 160 REM se PRINT cmd UNLISTI EN 170 190 200 panel control 460 PRINT cmd REMO TE PRINT cmd UNTALK PRINT cmd GO TO LOCAL voltmeter EXECUTE PRINT cmd TALK voltmeters 180 INPUT data reading t up voltmeter DISABLE disables front panel lockout 470 CLOSE voltmeters Initialising Devices EN voitmeter S EXECUTE REM voltmeter under control with EM voltmeter under front EM returns all devices to local control and A device may have been set up incorrectly or an error may have occurred Some devices have the capability of being returned to a known condition The SELECTED DEVICE CLEAR command may be used to return individual devices to a known state or the DEVICE CL
40. ice delimiting characters are used Consult the manufacturer s manual for each device to find out the delimiting characters for that device The computer defaults to the delimiting character Line Feed LF ASCII code 10 If a device requires different delimiting characters these may be specified using the END OF STRING command Example To set delimiting characters to carriage return line feed 80 PRINT cmd END OF STRING CHRS 13 5 10 The computer will then send these characters and expect to receive them after each data string until they are respecified Data Output Channels must be opened to the devices concerned as previously described Before data can be sent to the devices they must be listened using the LISTEN command Example 160 voltmeter OPENIN 9 3 180 PRINT cmd LISTEN voltmeter printer EXECUTE The EXECUTE command must follow the last device to be listened Data can then be sent to the devices through the DATA channel using the PRINT statement Example 190 PRINT data RI would set the range of the voltmeter and print RI on the IEEE printer When output has been completed the devices can be unlistened Example 340 PRINT cmd UNLISTEN Data Input Channels must be opened to the devices concerned as previously described Before a device can send data it must be talked using the TALK command Example 210 counter OPENIN
41. in progress flag remains set until the END end remote message is received it is then reset Note that the END end remote message received flag is not set Remote Messages ATN false DAB 1 data bytes disregarded by computer false DAB 2 etc false DABn and END the END remote message is not required if the number true of data bytes is not 0 Description The TRANSFER command can be used in two ways Example a The computer initiates the TRANSFER and after the talker has sent the specified number of data bytes exits the command Example b The computer initiates the TRANSFER and exits the command When the talker sends the END end remote message with the last data byte transferred the computer resets the TRANSFER in progress flag in the IEEE status word Thus the computer can undertake other tasks while the TRANSFER is in progress and detect its completion by reading the IEEE status word Associated Commands TALK UNTALK LISTEN UNLISTEN 54 TRIGGER Purpose To initiate simultaneous operation of the referenced devices Example 100 generator S OPENIN 9 110 voltmeter S OPENIN 14 120 PRINT cmd TRIGGER generator voltmeter EXECUTE Notes The last channel must be followed by the EXECUTE command IEEE Status Required before Execution The computer is controller in charge flag must be set TRANSFER in progress flag must be unset CLEAR command executed flag must b
42. ity C control function C1 C2 C3 complete capability C4 and C5 Note 1 This specification applies to the IEEEFS and interface hardware configured as system controller Note 2 The interface only sends and receives data when the computer addresses itself to talk or listen not when addressed by other devices Power supply 220 24OVAC 50 60Hz 3 watt Manufactured in accordance with BS415 79 Class 1 Designed and manufactured to comply with Acorn Computers Ltd 1MHZ Bus Peripheral Specification APPENDIX 5 FITTING THE IEEEFS EPROM CAUTION STATIC SENSITIVE DEVICES DO NOT HANDLE UNTIL YOU HAVE READ THESE INSTRUCTIONS Please read these instructions carefully before attempting this conversion If you are not completely confident of your ability to carry out this conversion yourself it will be in your own interests to take this unit to an authorised BBC Microcomputer dealer for him to carry out this upgrade 1 Determine which operating system is fitted in your computer by typing FX 0 and noting the version number displayed Switch off and disconnect the computer from the mains supply WARNING DO NOT REMOVE THE LID OF THE COMPUTER WHILST IT IS ONNECTED TO THE MAINS Unscrew the two large headed screws on the rear panel of the computer and the two large headed screws on the underside of the computer near the front Carefully remove the lid Unscrew the two or three on some computers bolts securing the keyboard assembly to
43. mmand executed flag must be set conflict for control of interface flag must be unset controller in process of acknowledging an unidentified command from another device flag must be unset IEEE Status After Execution The device or devices have been LISTENed flag is set Remote Messages ATN true MLA 1 true MSA 1 if specified true MLA2 true MSA2 if specified etc true MLAn true MSAn f specified Description The computer sends the MLA my listen address and MSA my secondary address if specified remote messages of the devices referenced by the previously OPENINed channels Associated Commands UNLISTEN 33 LOCAL LOCKOUT Purpose To prevent conflict between the remote and local operation of all devices Example 100 PRINT cmd LOCAL LOCKOUT IEEE Status Required before Execution The computer is controller in charge flag must be set TRANSFER in progress flag must be unset CLEAR command executed flag must be set conflict for control of interface flag must be unset computer in process of acknowledging an unidentified command from another device flag must be unset IEEE Status after Execution No change Remote Messages ATN True LLO Description After this command has been executed devices with a local lockout capability may only be returned to local front panel from remote interface control by using the GO TO LOCAL command Associated Commands REMOTE ENABLE REMOTE DISABLE LISTEN GO TO LOCA
44. nstant or variable Bit 3 specifies the sense of the response and Bits 0 2 specify the response IEEE Status Required before Execution computer is controller in charge flag must be set TRANSFER in progress flag must be unset CLEAR command executed flag must be set conflict for control of interface flag must be unset computer in process of acknowledging an unidentified command from another device flag must be unset The IEEE Status after Execution The device or devices have been LISTENed flag is reset Remote Messages ATN true true true true true true Associated Commands UNL MLA MSA PPC PPE UNL PARALLEL POLL DISABLE PARALLEL POLL UNCONFIGURE PARALLEL POLL REQUEST 36 PARALLEL POLL REUEST Purpose To conduct a parallel poll Example 100 PRINT cmd PARALLEL POLL REQUEST 110 INPUT cmd pollresponse Notes The response may only be returned to the least significant byte of an integer variable via the command channel IEEE Status Required before Execution The computer is controller in charge flag must be set CLEAR command executed flag must be set IEEE Status after Execution No change Remote Messages ATN IDY true true PPR Description If a TRANSFER is in progress then the computer waits until the current data byte has been transferred before conducting the PARALLEL POLL it then restarts the transfer In this way no data is lost If no TRANSFER is in progres
45. orn Computers authorised dealers Acorn Computers and II can accept no liability whatsoever for any loss or damage caused by service or maintenance by unauthorised personnel This manual is intended only to assist the reader in the use of the product and therefore Acorn Computers and II 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 manual or any incorrect use of the product WARNING THIS APPLIANCE MUST BE EARTHED IMPORTANT The wires in the mains lead for this appliance are coloured in accordance with the following code GREEN AND YELLOW EARTH BLUE NEUTRAL BROWN LIVE If the socket outlet available is not suitable for the plug supplied the plug should be cut off and an appropriate plug fitted and wired as described The plug which is cut off must be disposed of as it would be a potential shock hazard if it were to be plugged in with the cut off end of the mains lead exposed The moulded plug must be used with the fuse and fuse carrier firmly in place The fuse carrier is of the same basic colour as the coloured insert in the base of the plug Different manufacturers plugs and fuse carriers are not interchangeable In the event of loss of the fuse carrier the moulded plug MUST NOT be used Either replace the moulded plug with another conventional plug wired as described or obtain a replacement fuse carrier from an authorised BBC Microcomput
46. puter sends the MTA my talk address and if specified the MSA my secondary address remote messages of the device referenced by the previously OPENINed channel Associated Commands UNTALK 50 TIMEOUT OFF Purpose To disable timeouts Example 100 PRIN cmd TIMEOUT OFF Notes Timeouts are not a part of the IEEE488 standard TIMEOUT OFF is the default IEEE status IEEE Status Required before Execution No requirement IEEE Status after Execution The TIMEOUT ON flag is reset Remote Messages None Description With TIMEOUT OFF if a device fails to respond during a source or acceptor handshake then the ESC key must be pressed to exit from a command Associated Commands TIMEOUT ON 51 TIMEOUT ON Purpose To enable timeouts Example 100 PRINT cmd TIMEOUT ON Notes Timeouts are not a part of the IEEE488 standard TIMEOUT OFF is the default IEEE status IEEE Status Required before Execution No requirement IEEE Status after Execution The TIMEOUT ON flag is set Remote Messages None Description After this command has been executed and a device fails to respond in 2 55 seconds during a source or acceptor handshake then the appropriate timeout error is flagged in the IEEE status word Associated Commands TIMEOUT OFF 0 TRANSFER Purpose To initiate the transfer of data bytes between an active talker and all active listeners Example a 100 printer S OPENIN
47. r 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 IEEE socket is normally found on the rear of a device The IEEE488 standard permits individual cable lengths of up to 4 metres and a total cable length in a system of 2 metres per device or 20 metres whichever is the shorter Cables can be obtained from the manufacturers of devices When all devices have been connected to the interface turn on the power in the following sequence 1 devices 2 interface 3 computer The IEEE Filing System IEEEFS The IEEE488 interface of the BBC Microcomputer appears to the user as an additional filing system It gives the computer the ability to act as a controller talker or controller listener with the ability to pass control and request it back through the use of IEEEFS commands These commands enable the full use of an IEEE488 system without detailed knowledge of the operation of the interface The IEEEFS is selected by the command TEEE To reselect another filing system use the appropriate command DISK TAPE etc Note When used with BASIC the IEEEFS does not respond to CAT CHAIN EOF EXT LOA SAVE PTR D py Communication between a language and the interface is via two channels The first is the COMMAND channel used for transmitting IEEEFS commands and receiving information on the sta
48. rom the mains supply WARNING DO NOT REMOVE THE LID OF THE INTERFACE WHILST IT 15 CONNECTED TO THE MAINS Disconnect the IMHZ Bus connecting cable from the computer or other 1MHz bus peripheral The two halves of the case may be separated by undoing three fixing screws two on the rear panel and one on the underside in the centre at the front When reassembling push the two halves together whilst tightening the two rear fixing screws Take care not to lose the two captive nuts for the rear fixing screws which are pushed onto the upper moulding The four resistor packs RPI RP2 RP3 and RP4 are located on the PCB towards the front of the case Note the orientation of the resistor packs for future reference Carefully remove them using an IC extractor a small screwdriver used with extreme care will do and store them safely so that they can be refitted in the future should the interface become the last peripheral on the IMHZ bus Reassemble by following steps 2 and 3 in the reverse order INDEX Abbreviations Appendix 1 Assembler 60 BBC DEVICE NO 5 21 26 BGET 10 11 BPUT 10 CLEAR 6 19 20 21 27 CLOSE 5 COMMAND channel 4 21 Controller in charge 19 DATA channel 4 21 Data input 7 10 22 62 Data output 6 10 23 62 Delimiters 6 DEVICE CLEAR 17 29 END message 8 END OF STRING 6 30 EOI 8 EPROM fitting Appendix 5 EXECUTE 7 GO TO LOCAL 16 17 31 Group execute trigger 18 55 Hardware 64 IEEE488 stand
49. s User Guide Chapter 1 tells you how to connect the BBC Microcomputer s IEEE488 Interface to other IEEE488 devices and communicate with them Chapter 2 expands on this and covers the exchange of binary coded data Some IEEE488 devices have the ability to provide information on what state they are in and ways of obtaining this information are discussed in Chapter 3 Chapter 4 contains details of commands which can be used to change the state of IEEE488 devices The computer can pass control of the IEEE488 interface to another device and Chapter 5 tells how this is done Chapter 6 is useful for reference as it provides a glossary of IEEE488 commands in alphabetical order Information on using the interface in Assembler programs is contained in Chapter 7 Finally Chapter 8 gives some details of the hardware used in the interface Throughout this User Guide examples are given in BASIC However the interface can be used with any language running on the computer which permits the use of a filing system IEEEFS commands are given in full and in upper case However abbreviations and any mix of lower and upper case may be used See Appendix 1 for minimum abbreviations 1 GETTING GOING Simple data transfer Before connecting devices to the computer turn off the power to both interface and computer The interface can be connected to up to 14 other devices using IEEE488 standard cable assemblies These have a plug and socket at each end permitting sta
50. s the PARALLEL POLL is conducted immediately Associated Commands PARALLEL POLL ENABLE PARALLEL POLL DISABLE PARALLEL POLL UNCONFIGURE 87 PARALLEL POLL UNCONFIGURE Purpose To render all devices unable to take part in a parallel poll Example 100 PRINT cmd PARALLEL POLL UNCONFIGURE IEEE Status Required before Execution The computer is controller in charge flag must be set TRANSFER in progress flag must be unset CLEAR command executed flag must be set computer in process of acknowledging an unidentified command from another device flag must be unset IEEE Status after Execution No change Remote Messages ATN true PPU Associated Commands PARALLEL POLL ENABLE PARALLEL POLL DISABLE PARALLEL POLL REQUEST Ges READ BINARY Purpose To enable the input of a specified number of data bytes Example 90 DIM reading 5 100 recarder OPENIN 5 110 PRINT cmd TALK recorders 120 PRINT cmd READ BINARY 512 130 FORIS 0T0511 140 reading 1 BGET data 150 NEXT 160 CLOSEfrecorder 6 Notes Integer constants and variables in the range 1 to 67FFFFFF may be used for the number of data bytes IEEE Status Required before Execution The computer is controller in charge flag must be set TRANSFER in progress flag must be unset a device has been TALKed flag must be set CLEAR command executed flag must be set conflict for control of interface flag must b
51. sends the readings in the format N NNN CR LF 10 TEEE 20 cmd S OPENIN COMMAND 30 data OPENIN DATA 40 PRINT cmd BBC DEVICE NO 0 50 PRINT cmd CLEAR 60 PRINT cmd REMOTE ENABLE 70 PRINTfcmd END OF STRING CHRS 13 CHRS 10 REM sets delimiting characters to CR LF 80 voltmeter OPENIN 9 90 PRINTYkcmd UNLISTEN RINT cmd LISTEN voltmeters EXECUTE 110 PRINT data V5 120 RINT cmd UNLISTEN 130 PRINT cmd TALK Voltmeter P P P P FOR 1 1 TO 3 150 INPUT cmd voltageS 1 N P C 160 PRINT voltage 1 REM display on screen 170 180 190 EXT I RINT cmd UNTALK OSE Voltmeters Note In the above example the voltmeter had the same talk and listen addresses This is usually but not always the case Detailed information on each command can be found in Chapter 6 and minimum abbreviations are in Appendix 1 2 MORE ON DATA TRANSFER Binary Coded Data Sometimes it is necessary to send and receive more than 255 characters at a time without delimiting characters so the PRINT and INPUT statements cannot be used Devices such as spectrum analysers digital storage oscilloscopes and other microprocessor based devices with their own internal memory send and receive long fixed length sequenc
52. tatus after Execution Lists the status flags changed by the IEEEFS after successfully carrying out a command Remote messages Shows the logical state of the ATN remote message and the other remote messages sent by the IEEEFS Description A brief description of the command and its effect Associated Commands Similar commands and those which are concerned with the IEEE488 function 2 DB BBC DEV1CE NO Purpose To specify the primary address of the computer Example 100 TEEE 110 cmd OPENIN COMMAND 120 datas 0PENIN DATA etc 200 PRINT cmd BBC DEVICE NO 6 Notes Integer constants and variables in the range 0 30 may be used for the primary address IEEE Status Required before Execution No requirement IEEE Status after Execution The BBC DEVICE NO command executed flag is set Remote Messages None Description The computer stores the primary address which is set by the CLEAR command It requires a primary address so that after control has been passed to another device using the TAKE CONTROL command it may be addressed as a talker and control passed back to it This normally follows a REQUEST CONTROL command Associated Commands CLEAR 06 CLEAR Purpose To clear the interface Example 100 PRINT cmd BBC DEVICE NO address 110 PRINT cmd CLEAR IEEE Status Required before Execution The BBC DEVICE NO command
53. te of the interface The second is the DATA channel used for reading and writing data to other IEEE488 devices After the first use of IEEE the COMMAND and DATA channels must be opened Example 10 IEEE 20 cmd OPI 30 da FE tas oE ENIN COMMAND ENIN DATA If required these channels can be closed in the following way 1010 C 1020 C 5 E cmd Each device in an IEEE488 system must have a unique address Some devices have only one address a primary address whilst others have extended addressing primary and secondary addresses 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 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 more than one device in a system has the same address these can be changed by following the manufacturer s instructions Usually this involves changing switch settings on the rear of the device The OPENIN and OPENOUT functions are used to pass the primary and secondary if specified addresses of a device to the IEEEFS via a device channel Up to 14 channels may be open at one time Example A digital voltmeter has a primary address of 4 and no
54. the local lockout state by a previous LOCAL LOCKOUT command Associated Commands REMOTE ENABLE LISTEN LOCAL LOCKOUT GO TO LOCAL 41 REMOTE ENABLE Purpose To enable the remote operation of devices Example 100 PRINT cmd REMOTE ENABLE IEEE Status Required before Execution The CLEAR command executed flag must be set IEEE Status after Execution The REN remote enable message being sent flag is set Remote Messages REN Description After this command has been executed the computer can change devices from local front panel control to remote Interface control using the LISTEN command Associated Commands REMOTE DISABLE LISTEN LOCAL LOCKOUT GO TO LOCAL 42 REQUEST CONTROL Purpose To request that control be transferred back to the computer Example 100 PRINT cmd REQUEST CONTROL IEEE Status Required before Execution The computer is controller in charge flag must be set CLEAR command executed flag must be set computer in process of becoming controller in charge flag must be unset IEEE Status after Execution No change Remote Messages ATN sent by current controller in charge SRQ STB RQS and SRQ false when polled by controller in charge ATN sent by computer true after TCT received from current controller in charge Description The computer sends the SRQ service request remote message and then exits the command When the controller in charge condu
55. ty and returns the system to a knovvn state Data being transferred may be lost during this process The computer is then controller in charge Example 100 PRINT cmd CLEAR 20 6 THE IEEE FILING SYSTEM A Summary The IEEE488 Interface appears to the Operating System of the BBC Microcomputer as an additional filing system It is selected by the command KTEET The IEEEFS and the interface hardware is supplied so that the computer is system controller The computer can act as a controller talker controller listener with the ability to pass control to another device and request it back Channels Communication between a language and the IEEEFS is via two special channels The first is a COMMAND channel used for transmitting commands and receiving information on the state of the interface The second is the DATA channel used for reading and writing data Example 200 cmd OPENIN COMMAND 210 data s OPENIN DATA The IEEEFS maintains a status word accessible to the user which enables recovery from bus communication errors When a command is received from the language via the COMMAND channel the IEEEFS interprets it and checks the status word If it is satisfactory then the appropriate action is taken and finally the status word is updated The BBC DEVICE NO and CLEAR command should always follow the opening of the COMMAND and DATA channels 21 Device Addresses The OPENI

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