RE: Revisited: Sega XY freeplay

At 11:10 AM 9/1/99 -0700, Clay wrote:
>It's all software. You can find it pretty close to the beginning of the
>code in Star Trek at least.
> .snip.
>Since I never seem to get around to this, I'll look for my disassemblies of
>all the G-80 stuff. I think I noted the coin-timer in at least one...
>Probably a two-byte patch to just jump over it...
>

Like Clay said it's all in software. I looked at it a long time
ago when doing the security stuff so it all looks Greek now.
Here's the routine from Space Fury. I'm seem to remember that it's
the same for all games. Have fun!

L0095: LD B,#E7 ;INT due to COINA or COINB
L0097: IN A,(#F8) ;Check switch inputs, Active LOW
        AND D ;a = a .AND. /(initial input)
        JR NZ,#00A4 ;Don't JP if switch still pressed

        LD A,#A0 ;small delay
L009E: DEC A
        JR NZ,#009E
        DJNZ #0097 ;keep looking for switch release

        DEC B ;Release Timeout, B = #FF
L00A4: LD A,B ;switch released
        CP #C8 ;time the switch closure period
        JR NC,#00DA ;JP if timeout or period too short

COINOK: CALL #010A ;period OK, CALL COIN_COUNTER_INCR
        LD BC,#04FB ;In_PORT = #FB, DIP switches
        LD L,#00
        LD E,L ;E & L = #00
L00B2: IN A,(C)
        RRA ;Move DIP SW2-1 into E,b1
        RL E ;
        RRA
        RL L ;Move DIP SW2-5 into E,b0
        DEC C
        DJNZ #00B2 ;E(d3-d0) = SW2( 1,2,3,4 )
        LD A,L ;L(d3-d0) = SW2( 5,6,7,8 )
        CP E ;compare the two halves of the switch
        LD HL,#C80D
        JR Z,#00CB ;JP if SW2 positions identical
        BIT 7,D ;Complemented & Masked inputs, D7,6,5 of #F8
        JR NZ,#00CB ;D7 is COINA

        LD A,E ;SW2-1,2,3,4
        INC HL
        INC HL ;HL = #C80F
        .
        .
        .

It goes on from here but that's the meat of it.

David Fish | "We want...Information. INFORMATION
Melrose, MA USA | You won't get it!
   fishd@tiac.net | By hook or by crook we will"
   dfish@bev.etn.com | _The Prisoner_
Received on Wed Sep 1 17:13:38 1999