Control Panel DA: Fix overflowing paddle reads. Fixes #173

a2stuff · Dec 29, 2019 · af2e0ad · af2e0ad
1 parent 6c34fbe
commit af2e0ad
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Showing 2 changed files with 13 additions and 4 deletions.
diff --git a/desk.acc/control.panel.s b/desk.acc/control.panel.s
@@ -1504,19 +1504,26 @@ pdl3:   .byte   0
         ;; Let any previous timer reset (but don't wait forever)
         ldy     #0
 :       dey
+        nop                     ; Empirically, 4 NOPs are needed here.
+        nop                     ; https://github.com/a2stuff/a2d/issues/173
+        nop
+        nop
         beq     :+
         lda     PADDL0,x
         bmi     :-
 
         ;; Read paddle
-:       lda     PTRIG
-        ldy     #0
-        nop
+        ;; Apple IIe Tech Note #6 - The Apple II Paddle Circuits
+        ;; http://www.1000bit.it/support/manuali/apple/technotes/aiie/tn.aiie.06.html
+:       lda     PTRIG           ; Trigger paddles
+        ldy     #0              ; Init counter
+        nop                     ; ... and wait for first count
         nop
-:       lda     PADDL0,X
+:       lda     PADDL0,X        ; 11 microsecond loop
         bpl     done
         iny
         bne     :-
+        dey                     ; handle overflow
 done:   rts
 .endproc
 

diff --git a/mgtk/mgtk.s b/mgtk/mgtk.s
@@ -4623,6 +4623,8 @@ savesize:   .res 2
         bit     subid
         bvs     :+
 
+        ;; Apple IIc Tech Note #1 - Mouse Differences on IIe and IIc
+        ;; http://www.1000bit.it/support/manuali/apple/technotes/aiic/tn.aiic.1.html
         lda     #2                       ; default scaling for IIc/IIc+
         sta     mouse_scale_x
         lda     #1