New, shorter readjoy function

git-svn-id: svn://svn.cc65.org/cc65/trunk@1382 b7a2c559-68d2-44c3-8de9-860c34a00d81

diff --git a/libsrc/vic20/readjoy.s b/libsrc/vic20/readjoy.s
index a3cd1eddee43689ebab5fdbeed65eb9e1efa4e48..9aec6bd49c983b891596f93b67399a0747e17202 100644 (file)
--- a/libsrc/vic20/readjoy.s
+++ b/libsrc/vic20/readjoy.s
@@ -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