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New, shorter readjoy function

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git-svn-id: svn://svn.cc65.org/cc65/trunk@1382 b7a2c559-68d2-44c3-8de9-860c34a00d81
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cuz 2002-08-08 12:27:40 +00:00
parent 56fd8532ed
commit 76ee9a1f66
1 changed files with 26 additions and 56 deletions
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82
libsrc/vic20/readjoy.s
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@ -5,69 +5,39 @@
; unsigned readjoy (unsigned char joy);
;
.export _readjoy
.export _readjoy
.include "vic20.inc"
.include "vic20.inc"
.proc _readjoy
; The current implemenation will ignore the joystick number because we do only
; have one joystick
tax ; Joystick number into X
bne joy2
; Read joystick 1
.proc _readjoy
joy1: lda #$7F
ldx #$C3
sei ; necessary?
ldy VIA1_DDRA
stx VIA1_DDRA
ldx VIA1_JOY
sty VIA1_DDRA
ldy VIA2_DDRB
sta VIA2_DDRB
lda VIA2_JOY ; sw3 happens to be the 7th bit (i.e negative)
sty VIA2_DDRB
cli ; necessary?
; all this mess below tries to normalize the returned results (see joystick.h)
; by shifting bits around and inserting switch3 (right).
; easier (and far smaller) would have been just to return the bits where they
; lay and just #ifdef different joystick constants for the Vic20.
bmi s3_off ; must stay valid from the VIA2_JOY load
txa ; state: sw3 on, fire ?
and #$20 ; find out if fire has been pressed
bne f_off1
txa ; state: sw3 on, fire on
lsr
lsr
and #$07
eor #$1F
rts
f_off1: txa ; state: sw3 on, fire off
lsr
lsr
and #$07
eor #$0F
rts
s3_off: txa ; state: sw3 off, fire ?
and #$20 ; find out if fire has been pressed
bne f_off2 ; yeah, that's just about my sentiment by now
txa ; state: sw3 off, fire on
lsr
lsr
and #$07
eor #$17
rts
f_off2: txa ; state: sw3 off, fire off
lsr
lsr
and #$07
eor #$07
rts
; Read joystick 2 + (just return joy1)
lda #$C3 ; mask for VIA1 JOYBITS: sw0,sw1,sw2,sw4
ldx #$7F ; mask for VIA2 JOYBIT: sw3
sei ; necessary?
joy2: jmp joy1 ; stub for more joysticks (pointless?)
ldy VIA1_DDRA ; remember the state of DDRA
sta VIA1_DDRA ; set JOYBITS on this VIA for input
lda VIA1_JOY ; read JOYBITS: sw0,sw1,sw2,sw4
sty VIA1_DDRA ; restore the state of DDRA
and #$3C ; Mask relevant bits...
sta tmp1 ; ...and save for later
ldy VIA2_DDRB ; remember the date of DDRB
stx VIA2_DDRB ; set JOYBITS on this VIA for input
lda VIA2_JOY ; read JOYBIT: sw3
sty VIA2_DDRB ; restore the state of DDRB
cli ; necessary?
and #$80 ; Mask sw3
ora tmp1 ; Get sw0, sw1, sw2, sw4
eor #$BC ; Active states are inverted
rts
.endproc