Hello,
I am new to this list and I am trying to program the 2600 just for fun.
I have a problem detecting that the joystick button is pressed. I read
INPT4 but it always returns the same value !!!
So I made a small example program just to understand this point. I used
Nick S. Bensema "How to draw a playfield" and I removed all comments to
have a short listing that fit in this message.
Could someone tell me why this program does not work ? The background
color should change when the fire button is pressed.
BTW: It works with PCAE but not with the real VCS !
Are there any register initializations to do or something like that.
Thank you very much for your help !
Eric.
----- start of listing -----
include vcs2600.h
org $F000
Start
SEI
CLD
LDX #$FF
TXS
LDA #0
B1 STA 0,X
DEX
BNE B1
MainLoop
JSR VerticalBlank
JSR GameCalc
JSR DrawScreen
JSR OverScan
JMP MainLoop
VerticalBlank
LDA #2
STA WSYNC
STA WSYNC
STA WSYNC
STA VSYNC
STA WSYNC
STA WSYNC
LDA #44
STA TIM64T
LDA #0
STA WSYNC
STA VSYNC
RTS
GameCalc
LDA #0
STA COLUBK
LDA INPT4 ; It always returns
BNE NoButton ; the same value !!
LDA #$88
STA COLUBK
NoButton
LDA #$55
STA PF0
STA PF2
ASL
STA PF1
LDA #1
STA CTRLPF
RTS
DrawScreen
LDA INTIM
BNE DrawScreen
STA WSYNC
STA VBLANK
LDY #192
ScanLoop
STY COLUPF
STA WSYNC
DEY
BNE ScanLoop
RTS
OverScan
LDX #30
KillLines
STA WSYNC
DEX
BNE KillLines
RTS
org $FFFC
.word Start
.word Start
----- end of listing -----
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