!!! How to query the MultiJoy Interface

[{TableOfContents }] \\


!! 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|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:
(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!

Initializing:

{{{
PROC INITMULJOY()
 BYTE PACTL=$D302,PORTA=$D300
 ;
 PACTL==&$FB
 PORTA=$F0
 PACTL==%$04
RETURN

}}}
Query the Joystick:
{{{
PROC QUERYMULJOY(BYTE PL, BYTE POINTER STI,TRI)
 ; call procedure stating PL (range 0...3) and 2 variables to which the result is returned
 ; e.g. "QUERYMULJOY(0,ST,TR)" check for Joystick 0, return values in ST and TR

 BYTE PORTA=$D300, TRIG0=$D010, WSYNC=$D40A
 ;
 PORTA=(PL LSH 4)
 WSYNC=PL
 WSYNC=PL
 TRI^=TRIG0
 STI^=(PORTA&$0F)
RETURN

call the procedure with:

PROC MAIN()
BYTE TRI,STI,PL
BYTE POINTER S,T

S=@STI
T=@TRI

DO ; main loop

FOR PL=0 to 8 DO
 QUERYMULJOY(PL,S,T)
 ; STI now holds the value for the stick
 ; TRI now holds the value for the trigger
 ; go ahead and do something with it...
 OD
OD ; end of main loop



}}}

!! Quick

to be added 

!! FORTH

to be added