How to query the MultiJoy Interface
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How to query the MultiJoy Interface#

Table of Contents


General Information#

The MultiJoy is an adapter to connect 8 or 16 Joysticks to a ATARI 8Bit (600XL, 800XL, 130XE, ...). The MultiJoy was designed by Radek Sterba (RASTER). You can find detail Information on thi adapter on http://www.infos.cz/raster/atari/hw/multijoy.htm

Mathy van Nisselroy has information about MultiJoy Games on his site --> http://www.mathyvannisselroy.nl/special%20stuff.htm

Assembler / Machine Language#

First you must initialize the communication direction of the ports. The pins of Joystick 1 work as Input and the pins of Joystick 0 work as output.

This has to be done once at the start of the program. 

  LDA #$30	 ; clear BIT 2 of PACTL (direction control register)
  STA $D302      ;PACTL, control read/write direction with PORTA
  LDA #$F0	 ;4 upper bits=OUT (Joystick 1),4 lower bits=IN (Joystick 0)
  STA $D300      ;PORTA, set directions
  LDA #$34	 ; restore OS default value for PACTL 
  STA $D302      ;PACTL

Now we can query the joysticks: 

  LDA #0	  ;Number of the Joystick to query (0-7 for MultiJoy, 0-15 for MultiJoy16)
  ASL A		  ; multiply by 16
  ASL A
  ASL A
  ASL A
  STA $D300       ;PORTA, select Joystick to read
  LDA $D300       ;PORTA, read value
  AND #$0F	 ; mask out upper 4 bits

The joystick button can be queried after selection of the joystick with register TRIG0: 

  LDA $D010  ;TRIG0

You must take care to synchronize the queries. Especially take care that not players on the first Joysticks have any unfair opportunities.

Basic / Turbo Basic#

BASIC#

Initializing: 

POKE 54018,48 : REM control read/write direction with PORTA
POKE 54016,240 : REM 4 upper bits=OUT (Joystick 1),4 lower bits=IN (Joystick 0)
POKE 54018,52 : REM restore OS default value for PACTL

Query the Joystick: 

POKE 54016,NUM*16 : REM NUM = Number of Joystick (0-7/0-15)
ST=PEEK(54016):ST=ST-INT(ST/16)*16 : REM read Joystick value
TR=PEEK(53264 ) : REM read Trigger value directly from GTIA

TURBO BASIC#

Initializing: 

POKE $D302,$30
POKE $D300,$F0
POKE $D302,$34

Query the Joystick: 

POKE $D300,NUM*$10 : REM NUM = Number of Joystick (0-7/0-15)
PAUSE %10 : REM wait for value
ST=PEEK($D300)&$0F : REM read Joystick value
REM ST=STICK(%0) - this does not work properly, because the Joystick value 
REM which is read from register 632 is only updated every 1/50th second
REM TR=STRIG(%0) : REM this does not work either
TR=PEEK($D010): REM read it directly from the GTIA register

ACTION!#

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Quick#

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FORTH#

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