On Saturday 30 August 2003 18:05, KirkIsrael@xxxxxxxxxxxxx wrote:
> screen values are restored. I do a tight loop until
> the select button is released, to prevent multiple counting
> of the select, but that didn't work.
I'd been wrestling with the same problem lately. I haven't
actually written the code to fix it, but here's the theory I
came up with while driving home one night this week :P (I guess
I'll write my theory in assembler here and work it into what you
posted, but no guarantees it'll build... I don't even have dasm
on the same machine as my mail client at the moment.)
This costs a byte (actually 4 bits, so I guess I'll stick your
playercount flag in a 5th) of RAM. Suppose that byte is called
SwitchFlags. The effect I'm envisioning is that if you hold
down the select key, the number of players gets toggled about
twice a second (more useful for games with more than 2 options
accessible by select) but the display of the title screen isn't
otherwise disturbed. (Holding down the reset button should
result in the first frame of your game being displayed till you
let go, but unless you start some annoying music on the first
frame like Parker Bros. Frogger I think this is okay ;) )
TitleStart
; if we've jumped here, we don't want to switch the player
; mode... Kirk, I actually don't get what this is here for
JMP DoneSwitchingPlayerCount
; if we jump HERE, we want to deal with the switches...
HandleSwitches
LDA SWCHB
AND #%00000001 ;is game start down?
BEQ CheckSelect ; if not, try select
JMP MainGameStart
CheckSelect
LDA SWCHB
AND #%00000010 ;is game select down?
BNE SelectIsDown
LDA #%11110000 ; if not, clear keybounce timer
ORA SwitchFlags
STA SwitchFlags
JMP DoneSwitchingPlayerCount
SelectIsDown
LDA SwitchFlags
AND #%00001111 ; check keybounce timer
BEQ TogglePlayerCount ; if not waiting, toggle the player count
DEC SwitchFlags ; otherwise, tick the clock and wait some more
JMP DoneSwitchingPlayerCount
TogglePlayerCount
LDA SwitchFlags
EOR #%00010000 ; toggle player count bit
ORA #%00001111 ; reset keybounce timer
STA SwitchFlags ; and save....
DoneSwitchingPlayerCount
(VBLANK code continues....)
Rob
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