Electron Plus 1 User Guide
Contents
1. The Electron Plus 1 User Guide Date March 1984 Exposure Like most electronic equipment the Electron Plus 1 should not be exposed to direct sunlight or moisture for long periods Copyright Acorn Computers Limited 1984 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 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 in good faith However it is acknowledged that there may be errors or omissions in this manuaL A list of details of any 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 Limited Fulbourn Road Cherry Hinton Cambridge CB1 4JN All maintenance and service on the product must be carried out by Acorn Computers authorised dealers Acorn Computers can accept no liability whatsoever for any loss or damage caused by service or maintenance by unauthorised personnel This manu2. Although the analogue interface is most often used for connecting games paddles or joysticks it may also be used to measure voltages from other devices such as light sensitive or heat sensitive transducers as long as they are electrically compatible see Choosing other analogue peripherals below The analogue interface has a resolution of 8 bits ie 1 in 256 but generates numbers in the range 0 to 65280 for compatibility with BBC BASIC The Plus 1 can continuously measure up to four voltages allowing the use of up to four games paddles two joysticks or four separate external voltages at a time Wherever the analogue inputs originate they are treated exactly the same by the analogue interface and computer Connecting to the analogue in socket Analogue peripherals which have been manufactured by Acorn for the Electron may simply be plugged into the analogue in socket Before connecting other peripherals check that they are electrically compatible dealt with separately for each type below and that the cable used is wired correctly ending in a 15 way D type connector wired as follows Figure 3 The analogue in socket viewed from outside case The analogue interface 7 Pin number Signal name Description 1 5V 5 volt power for digital circuit 2 OV 0 volt power for digital circuit 3 OV 0 volt power for digital circuit 4 CH3 Analogue input 3 5 Analogue Gnd 0 volt for analogue circuit 6 OV 0 volt power for
3. Appendix A 20 Summary of new and changed FX commands and OSBYTE calls 20 FX3 X 20 FX5 X 20 FX6 X 20 FX 16 X 20 FX 17 X 20 FX21 X 21 FX 140 X 21 FX 163 128 X 21 FX225 X 21 FX 226 X 21 FX227 X 22 FX229 X 22 FX230 X 22 From assembly language only 22 1 Introduction The Acorn Electron Plus 1 adds the following capabilities to your Acorn Electron computer Four 8 bit analogue to digital input channels to allow the use of up to two joysticks or four games paddles or measurement of up to four analogue voltages A parallel port for connecting a printer with a Centronics compatible interface Two cartridge slots for installing Acorn Electron approved games utility application or language ROMs or additional expansion devices The ROMs may either hold files as a ROM filing system or be paged sideways language ROMs All of these facilities are accessed using simple BASIC or machine operating system MOS commands which are compatible with BBC BASIC The different typefaces used You will notice that some letters words and phrases in this manual have been printed differently from the rest of the text This is to help you tell the difference between explanatory text words which appear on the screen and certain keys on the computer keyboard Ordinary text appears like this or like this for emphasis Text typed in at the computer or displayed on the screen appears like this Words like RET
4. their keycaps FX226 2 255 function keys in this range will generate an ASCII code based on the second parameter FUNC A produces a code the same as the second parameter FUNC B a code one higher etc 22 Appendix A FX227 X Changes the effect of typing the remaining function keys Q to Z plus as follows FX227 0 ignores function keys in this range FX227 1 function keys in this range will generate the BASIC keywords marked on their keycaps FX227 2 255 function keys in this range will generate an ASCII code based on the second parameter FUNC Q produces a code the same as the second parameter FUNC R a code one higher etc FX229 X Alters the effect of pressing the ESCAPE key as follows FX229 0 pressing ESCAPE will interrupt the BASIC program FX229 1 pressing ESCAPE will not interrupt the BASIC program but generate ASCII code 27 decimal FX230 X Enables or disables the normal action of the ESCAPE key as follows FX230 0 enables ESCAPE FX230 1 disables ESCAPE From assembly language only The following OSBYTE function is only accessible from assembly language not as a FX command To read the analogue inputs call OSBYTE with A 128 decimal and X 0 to 4 as follows X 0 returns number of last channel sampled and converted in Y X 1 4 returns last reading from channel specified in X as 16 bit integer in X low byte and Y high byte Notes 2 COMPUTE PUTER
5. URN mean that you press the key marked RETURN rather than actually type the letters RE TU R N 2 Setting up Installing the Electron Plus 1 Unplug your Electron computer from the mains turn off the mains socket remove the mains plug and then the power cable from the side of the Electron You may also find it convenient to unplug any other cables to the television or cassette drive from your Electron to make installation easier Warning Never install or remove the Electron Plus 1 with the power to the Electron turned on Turn the Electron upside down with the expansion connector at the rear of the computer towards you and remove the plastic cover from the connector to expose the edge connector fingers Take the Electron Plus 1 out of its packaging and check that the threaded ends of the two large Screws are not protruding through the base of the Plus 1 if they are press them down so that the threaded ends are flush with the base Turn the Plus 1 upside down and locate the Electron s expansion connector in the mouth of the edge connector socket on the Plus 1 and push them together firmly Figure 1 Fitting the Plus 1 to the Electron Setting up 3 Using a small coin or screwdriver screw the two large screws in the Plus 1 into the Electron Do not overtighten If the screws do not engage in the threads in the base of the Electron try reseating the Plus 1 on the Electron s expansion connector The Plus 1 should now be fir
6. al is intended only to assist the reader in the use of this product and therefore Acorn Computers 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 First published 1984 Published by Acorn Computers Limited Fulbourn Road Cherry Hinton Cambridge CB1 4JN Typeset by Bateman Typesetters Cambridge Contents 1 Introduction mO The different typefaces used 2 Setting up Installing the Electron Plus 1 Using a printer Using games paddles or joysticks Using cartridges Using tape cassettes with the Plus 1 Disconnecting the Plus 1 3 The analogue interface ON BRBRwWWN Lb Connecting to the analogue in socket Choosing a games paddle Choosing a joystick Choosing other analogue peripherals Using the analogue interface from BASIC Using the analogue interface from assembly language 4 Using a printer Choosing a printer Connecting a printer Setting printer characteristics Printing from BASIC The internal printer buffer Printing from assembly language OOo A a AS ANnNKRWNN VN 5 Using cartridges Games and applications ROM file cartridges Languages paged ROM cartridges Ro Za ION 6 Dealing with problems 18 Improving processing speed 18 Problems which may not be faults 18 Electron malfunctioning 19 Peripherals malfunctioning 19
7. as follows buttons 0 means no buttons are being pressed buttons 1 means that push button 0 is being pressed buttons 2 means that push button 1 is being pressed buttons 3 means both push buttons are being pressed Each analogue input is sampled in turn and converted to the digital result returned by ADVAL in order of decreasing channel number The conversion process takes 10mS ec ie one hundredth of a second per active channel so with all four channels operating there will be a delay of 40mSec between changes in the readings To reduce this delay you should turn off channels you are not using with the FX16 command as follows FX16 0 turns all the analogue channels off FX16 1 turns channel 1 on and channels 2 to 4 off FX16 2 turns channels 1 and 2 on and channels 3 and 4 off FX16 3 turns channels 1 to 3 on and channel 4 off FX16 4 turns all four channels on 10 The analogue interface To force a particular channel to be sampled and converted next use FX17 channel as follows 2010 FX17 3 2015 REM force sampling and conversion for channel 3 2020 REPEAT UNTIL ADVAL 0 DIV 256 3 REM wait till finished channel 3 2030 reading ADVAL 3 REM get reading from channel 3 Note that the Fx17 command forces sampling and conversion for all channels from that specified down to 1 even if they have been turned off with FX16 ADVAL 0 DIV 256 returns the number of the last channel to compl
8. ation eg with the same software if not try cleaning and reseating the connectors If the peripheral does work in the original situation check the things that are different in the fault situation If the peripheral has not worked before check that you have connected and initialised it correctly Try swapping it with another borrowed from a friend or dealer and try it with other software If other peripherals work yours is probably incompatible or faulty return to dealer if other software works with your peripheral change your software if changing peripherals and software does not work try cleaning the connectors as described above Electron malfunctioning Perhaps your peripheral requires special software before it will work correctly such as a printer driver Appendix A Summary of new and changed FX commands and OSBYTE calls This Appendix provides a summary of the FX commands available to users of the Electron with an expansion unit fitted which either are not documented in the Electron User Guide or are documented incompletely These commands may also be used in assembly language by a call to OSBYTE commands which can only be used from assembly language are summarised at the end of this Appendix FX3 X Selects the device to which printed output is sent as follows FX3 0 To screen and printer FX3 10 To printer only FX3 4 To screen only FX3 6 To neither device FX5 X Selects the printer dri
9. ck one for left right so that a joystick provides two 8 The analogue interface dimensions of information to the software that is using it Joysticks will usually also have a small pushbutton switch or fire button providing the computer with a digital pressed not pressed signaL To make the best use of the analogue interface you should buy a high resolution joystick with an impedance of at least 10k ohms wired as described above see Connecting to the analogue in socket Check the joystick for ease of use and comfort ideally by connecting it to an Electron in the shop and using it with the type of game or other program that you will want to use at home You will probably find a self centering design more suitable for games playing but less convenient for general purpose use The model ANHOI joysticks provided by Acorn are ideally suited for use with the Electron Plus 1 Choosing other analogue peripherals Devices other than joysticks and games paddles may be connected to the analogue interface provided that they are electrically compatible with it and are wired as described above see Connecting to the analogue in socket The peripheral may either generate a DC voltage in the correct range itself which is proportional to the measurement or may take the reference voltage VREF from the interface and return a fraction of it which is proportional to the measurement ie may act as a potential divider If the perip
10. d the ROM filing system When you break out of a game the ROM filing system will be active instead of the cassette filing system The commands available are CAT LOAD and CHAIN which have identical functions to their cassette equivalents but work with the ROM files To use the cassette filing system select it by typing TAPE to use the ROM filing system again type ROM Using cartridges 17 With two ROM file cartridges plugged in to use the software in the cartridge further from the keyboard list the files in the ROMs using CAT and try CHAINing the file listed after BOOT for that cartridge Languages paged ROM cartridges Language cartridges contain alternative programming languages eg LISP or other utilities which the Electron can use instead of the more familiar BASIC language These ROMs are called paged ROMs and are switched by the Electron into the same address range amp 8000 to amp C000 as the BASIC ROM they are replacing This is a very effective way of increasing the power of your Electron system without using up more RAM memory space When you first switch on if there are no games or applications cartridges plugged in any language ROM will be selected in preference to BASIC if there are two languages the one nearer the keyboard will take priority To switch between language cartridges and BASIC use the language name preceded by an asterisk eg BASICor LISP 6 Dealing with problems The follow
11. digital circuit 7 CHI Analogue input 1 8 Analogue Gnd 0 volt for analogue circuit 9 Not connected 10 PB1 Pushbutton 1 digital input 11 VREF Voltage reference for analogue circuit 1 8V 12 CH2 Analogue input 2 13 PBO Pushbutton 0 digital input 14 VREF Voltage reference for analogue circuit 1 8V 15 CHO Analogue input 0 Choosing a games paddle Games paddles usually consist of a small box with a single rotating knob providing the computer with a voltage indicating how far the knob has been rotated A games paddle can therefore only provide a single dimension of information to a game such as a position in the horizontal or vertical axis of the screen The games paddle may also have a small pushbutton switch or fire button providing the computer with a digital pressed not pressed signal The games paddle should have an impedance of at least 10k ohms to match the analogue circuitry of the Plus 1 and be wired as described above see Connecting to the analogue in socket Check the paddle for ease of use and comfort ideally by connecting it to an Electron in the shop and using it with the type of game or other program that you will want to use at home Choosing a joystick Joysticks usually consist of a small box with a lever protruding from the top which is free to move up to approximately 30 degrees in any direction about a pivot at its base This position of the joystick lever is translated into two voltages one for front ba
12. ete sampling and conversion or 0 if no channel has yet completed conversion since the last FX16 or FX17 command Using the analogue interface from assembly language The functions of the ADVAL keyword in BASIC are provided by calling OSBYTE with A amp 80 128 decimal and X a number in the range 0 to 4 which determines the function performed as follows X 0 on exit Y will contain the number of the last channel sampled and converted or O if no conversion has yet completed since the last FX16 or FX17 call X 1 to 4 on exit X and Y will contain the last value sampled and converted for the channel number specified in X X contains the least significant eight bits and Y contains the most significant eight bits The range and significance of this 16 bit integer is as for the value returned by ADVAL see Using the analogue interface from BASIC FX commands can be performed in assembly language in the usual way by a call to OSBYTE amp FFF4 Thus to set the number of analogue input channels instead of using FX16 lt number load A with amp 10 and X with the number then call OSBYTE to force a channel to be sampled and converted FX17 lt channel load A with amp 11 and X with the channel number then call OSBYTE Each time the sampling and conversion of an analogue signal is completed an event is generated If you wish to detect and act on this event you must first The analogue interface 11 place
13. henever you use LOAD SAVE CHAIN LOAD RUN or EXEC the Plus 1 printer port and analogue interface are automatically disabled for the duration of that command If you are using the BPUT BGET INPUT or PRINT commands in a program you should use the F X163 128 1 command to explicitly disable the printer port and analogue interface before using the tape and re enable them afterwards using F X163 128 0 Disconnecting the Plus 1 If you should need to disconnect the Plus 1 for any reason be careful to turn off the Electron first then reverse the sequence of actions used to attach it Note that the Plus 1 should not be disconnected and reconnected repeatedly as this will cause wear of the expansion connector contacts uppermost Setting up 5 Figure 2 A typical expanded Acorn Electron system 3 The analogue interface The analogue interface is used to measure smoothly varying voltages analogue inputs produced outside the computer converting them into numbers digital information which the Electron can then use like any other numerical input This conversion is performed by a circuit known as an analogue to digital converter or ADC The analogue inputs are connected via the analogue in socket which is the left hand socket when viewed from the rear of the Plus 1 This socket also allows you to detect the position of two two way switches normally connected as the fire buttons on joysticks or games paddles
14. heral uses the reference voltage from the interface Minimum impedance of 10k ohms If the peripheral generates its own voltage DC voltage 0 to 1 8 volts Current drive 1 milliamp minimum The maximum resolution of the analogue to digital conversion is 8 bits ie the analogue input will be converted into one of 256 different numbers depending on the input voltage If you wish to measure absolute voltages you must first calibrate the system against a reliable voltage reference The analogue interface 9 Using the analogue interface from BASIC The four analogue voltages being read by the Electron are assigned channel numbers in the range 1 to 4 to read the voltage on a channel use the BASIC function ADVAL minimum abbreviation AD token amp 96 For example horizontal ADVAL 1 vertical ADVAL 2 The variables horizontal and vertical will now contain integers in the range 0 to 65280 proportional to the voltages measured on channels 1 and 2 with V being read as approximately 0 and 1 8V as approximately 65280 The number returned by ADVAL increases by steps of 256 rather than by 1 ie 0 256 512 65280 to allow for future expansion in the resolution of the conversion process To determine whether the fire buttons on the paddles joysticks are being pressed use ADVAL with a channel number of 0 for example buttons ADVAL 0 AND 3 The value of the variable but t on s then tells you which buttons are being pressed
15. ing is a brief guide to diagnosing problems that may occur when using the expansion interface and details of solutions which can be reached without technical assistance or voiding the warranty Do not open the Electron computer or Plus 1 cases as any modifications you make to this equipment may void the warranty If in doubt consult your dealer Improving processing speed With the Plus 1 attached the Electron has considerable extra processing to do supervising the extra facilities This will usually not be noticeable but the following steps may be useful to minimise the speed decrease Use MODEs 4 to 6 as advised in the Electron User Guide Turn off any ADC channels that are not needed see Using the analogue interface from BASIC chapter 3 Disable all servicing of input and output via the Plus 1 using FX163 128 1 and re enable servicing with FX163 128 0 when required Problems which may not be faults Tape filing system commands aren t working you must switch to the tape filing system TAPE RETURN after using cartridges see chapter 5 Tape loading error to reduce data errors avoid using MODES 0 to 3 while loading and saving to tape If you are using the tape for data storage PRINT INPUT BPUT BGET try the suggestions for improving processing speed given above for the duration of the tape operations Cannot return to BASIC from a cartridge some cartridges are protected against p
16. iracy by disabling the BREAK key To use BASIC remove the cartridge and then press BREAK See chapter 5 for further details Programs that cannot run with the Plus 1 but work without it try the suggestions for improving processing speed above Dealing with problems 19 Electron malfunctioning Disconnect the Plus 1 If the computer still does not work check the power then take the Electron and the Plus 1 to your dealer if the computer works continue reading Clean the edge connector fingers at the rear of the Electron using a nonabrasive rubber and a soft cloth then try reconnecting the expansion interface with all the peripherals disconnected If the computer still does not work take the Plus 1 to your dealer otherwise continue reading Reconnect each peripheral including cartridges in turn until the original fault returns cleaning any contacts that seem dirty or tarnished If the fault does not return you have probably removed it by cleaning and reconnecting the connectors if the fault does return continue reading Check the offending peripheral for obvious faults bent pins in the connector breaks in cables bad seating in the sockets Try the suggestions under Peripherals malfunctioning below Return the item to your dealer with a description of the fault Peripherals malfunctioning Check the orientation and seating of the connectors If the peripheral has worked before check if it still works in that situ
17. l output displayed on the screen will then be sent to the printer as well To turn printing off type CTRL C or execute VDU 3 in a program For full details of using a printer see chapter 4 Using games paddles or joysticks Only use games paddles or joysticks which are compatible with the Plus 1 ask your dealer or see chapter 3 Turn the Electron off and plug the cable into the Plus 1 analogue in socket which is the smaller socket at the rear to the left of the printer socket The plug and socket are shaped so they will only fit together 4 Setting up one way up Turn the Electron on again and the joysticks or games paddles are now ready for use with suitable games or can be read from BASIC see chapter 3 for further details Using cartridges To use a cartridge produced by Acorn for the Plus 1 you must first plug it into either of the two shuttered slots in the top of the Plus 1 Insert the cartridge with its label towards you ie facing the keyboard pushing it into the slot so that the right hand end makes contact first then pressing it home until you hear it click into place The cartridges are designed so that it is very difficult to insert them the wrong way round With a cartridge inserted correctly either press BREAK if the Electron was turned on or turn the Electron on Instructions in the use of the cartridges vary full details will be supplied with any cartridge you purchase Using tape cassettes with the Plus 1 W
18. mly attached to your Electron Turn the Electron over and plug the power supply and any other cables you may have removed into the Electron and turn it on Check that the Electron still works normally by loading and running a small program which you know has run successfully before If all is not well refer to chapter 6 Now you have fitted the Plus 1 to the Electron and checked that the system works you can connect your printer joysticks games paddles or cartridges Using a printer To connect a printer you will need an extra mains socket or an adapter to power the printer and an interface cable to connect the printer to the Plus 1 You should be able to obtain a suitable cable from your dealer Put the printer on a stable flat surface near enough to your Electron so that the interface cable can reach Turn both the Electron and the printer off Connect the printer cable to the printer as instructed in the printer manual then connect the other end of the cable to the Plus 1 as follows The printer socket is the wide rectangular socket at the rear of the Plus 1 to the right of the analogue input socket viewed from the rear Insert the printer cable plug in this socket so that the triangular mark on the socket housing lines up with the similar mark on the plug Turn the printer and Electron on again You are now ready to use the printer for simple printing tasks To turn printing on type CTRL B or execute VDU 2 in a program al
19. r ie FX6 lt ASCII code gt can be used to stop that single character being sent to the printer If output to both printer and screen is selected see Printing from BASIC you can get a printer ignore character out to the printer by sending it immediately after executing a VDU 1 command or typing CTRL A Printing from BASIC When you first switch on all output will be sent to the screen to get printed output type CTRL B or execute the command VDU 2 to send the output to the current printer driver as welL To stop sending output to the printer driver either type CTRL C outside a program or execute the command VDU 3 To alter the way that output is routed use the FX3 command as follows Output to Output to current printer screen FX3 0 Y Y FX3 10 Y N FX3 4 N Y FX3 6 N N With the printer only selected after X3 10 all output will be sent to the printer and CTRL B and CTRL C will have no effect With both screen and printer selected after switching on or using FX3 0 a single character can be sent to the printer but not to the screen by preceding it with CTRL A or VDU 1 ina program Use this method to send the printer ignore character or any codes that might have unwanted effects if sent to the screen it is probably simplest to use CTRL A or VDU 1 before any ASCII code in the range 0 to 31 Using a printer 15 The internal printer buffer Text sent to the printer is first stored in an area of comp
20. r of the Plus 1 being careful to insert it the right way up with the arrow head on the plug facing upwards Turn the printer and Electron on and you are now ready to start printing see Setting printer characteristics below Using a printer 13 26 way ribbon cable connector Figure 4 The completed printer cable Setting printer characteristics Whenever you switch the Electron on it will return to its default printer characteristics which may be changed as follows Output for the printer is sent to it by software known as a printer driver which handles tasks such as queueing text for printing and checking that the printer is ready for another character before sending it When you first switch on the standard printer driver is selected which sends output for printing to the 14 Using a printer printer port You may switch between using this driver and another known as the printer sink with the FX5 command as below FX5 0 selects the printer sink which causes output for the printer to be ignored this is useful when printed output is not required or a printer is not connected FX5 1 selects the standard printer driver The printer driver will ignore the line feed at the end of text lines and just send a carriage return to the printer port If your printer requires a line feed at the end of each line you can restore it by using FX6 0 The FX6 command actually sets the printer ignore characte
21. rtridges can be plugged These cartridges can provide games languages utilities application programs or other facilities Contact your local dealer for a list of cartridges currently available Full instructions in the use of these cartridges will be provided with the individual cartridges Cartridges should not be installed or removed with the Electron switched on If you remove or install a cartridge with the computer turned on you will need to press BREAK or CTRL BREAK to restore normal operation Games and applications cartridges will usually behave quite differently from language cartridges so they are described separately below Games and applications ROM file cartridges These cartridges are usually designed to load and run the software they contain automatically taking over operation of the Electron when it is turned on or after pressing CTRL BREAK so that the Electron behaves as a machine dedicated to running that program while the cartridge is plugged in To defeat this mechanism you should press CTRL BREAK wait about one second and then press ESCAPE If you have two games applications cartridges plugged in the one at the front nearest the keyboard will be the one that takes over the Electron The programs and data used by these cartridges are contained in ROMS accessed by a filing system similar to the cassette tape filing system you are used to but much faster and restricted to reading information only This is calle
22. the address of the code to handle it and any other events you are going to enable at location amp 220 and then enable the event using FX14 3 or the equivalent assembly language code LDA amp E LDX 3 JSR OSBYTE The event code passed to your routine for this event in A is 3 For further information refer to Events in chapter 29 of the Electron User Guide To disable handling of this event use FX13 3 or the equivalent assembly language code LDA amp D LDX 3 JSR OSBYTE 4 Using a printer Choosing a printer The Electron Plus 1 will work with a wide range of printers using a Centronics compatible parallel interface If in doubt about the suitability of a particular printer consult your dealer A helpful and impartial booklet on choosing printers entitled USPE C 32a is available free from the Council for Educational Technology 3 Devonshire Street London WIN 2BA Connecting a printer To connect a parallel printer to the Plus 1 you will need a suitable cable These are available from your dealer as Acorn part number ANG04 The connections in the cable are as follows Signal name 36 way plug pin number 26 way plug pin number Strobe 1 Data0 2 3 Datal 3 5 Data2 4 7 Data3 5 9 Data4 6 11 Data5 7 13 Data6 8 15 Data7 9 17 Acknowledge 10 19 Ground 19 to31 Even numbers 2 to 24 Turn the printer and Electron off and connect the printer to the printer socket the right hand socket when viewed from the rea
23. uter memory known as the internal printer buffer and only sent on to the printer when the printer can handle it usually a line or a character at a time If you wish to remove all remaining text from the buffer you can usually either press ESCAPE which empties all the buffers on the system or use the command FX21 3 which empties the printer buffer only You can disable the emptying of all buffers on pressing ESCAPE with the command FX230 1 and enable it again by FX230 0 Your printer may also have its own printer buffer so that printing may continue for a short while after using ESCAPE Printing from assembly language The FX commands given above may be accessed from assembly language in the usual way ie by loading A with the command number and X with the number following the comma then calling OSBYTE amp FFF4 eg to flush the printer input buffer FX21 3 LDA amp 15 LDX 3 JSR amp FFF4 Text is printed by selecting printed output with the assembly language equivalents of FX3 0 or FX3 10 and then sending the characters to be printed one at a time by loading the accumulator with the ASCII code and calling OSWRCH amp FFEE for each character in turn If output to screen and printer is selected FX3 0 the text to be printed must be preceded by ASCII 2 CTRL B and followed by ASCII 3 CTRL C as when using BASIC 5 Using cartridges The Plus 1 has two sockets in its upper surface into which a variety of ca
24. ver as follows FX5 0 To printer dump FX5 1 To printer port FX6 X Selects the printer ignore character specified by the ASCII code X FX16 X Selects the number of analogue to digital conversion channels where X is a number in the range 0 no channels to 4 all four channels FX17 X Forces analogue to digital conversion to restart for channels X to 1 Appendix A 21 FX21 X Flushes empties the buffer specified by the second parameter as follows FX21 0 flushes the keyboard buffer FX21 3 flushes the printer output buffer FX21 4 7 flush sound output buffer number 0 1 2 or 3 FX140 X Selects the cassette filing system with any value of X FX163 128 X Enables or disables input output through the Plus 1 FX163 128 0 enables printer and ADCs FX163 128 1 disables printer and ADCs FX225 X Changes the effect of typing the user defined function keys as follows FX225 0 ignores the function keys FX225 1 the function keys will generate the character string defined by the user FX225 2 255 the function keys will generate an ASCII code based on the second parameter f1 generates a code one more than the second parameter f2 a code two more etc FX226 X Changes the effect of typing function keys in the range A to P as follows FX226 0 ignores function keys in this range FX226 1 function keys in this range will generate the BASIC keywords marked on
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