How to query the MultiJoy Interface#
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 this adapter on Radeks website
Mathy van Nisselroy has information about MultiJoy Games on
his site
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: (proceed a delay 30 cycles at least between write to PORTA register and following reading of PORTA or TRIG0. )
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 LDX #$06 ;Here is a delay 30 cycles before reading of PORTA WAI DEX BNE WAI 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!#
to be added
Quick#
to be added
FORTH#
to be added