Add note about zpage E0,E1,E2 HPOSN

2017-10-30 08:14:48 -07:00 · 2017-10-30 08:14:48 -07:00 · 335fbc1a68
parent 85f890a30e
commit 335fbc1a68
1 changed files with 5 additions and 3 deletions
--- a/src/dhgr.byte.s
+++ b/src/dhgr.byte.s
@ -720,7 +720,7 @@ OnLoadSprite
 LoadRows
 ; Y -> Source Address
        LDA gSpriteY
-        JSR GetHgrBaseAddr
+        JSR GetHgrBaseAddr  ; cursor_row is updated -> HPOSN

        LDA cursor_col
        STA gSpriteX
@ -1129,6 +1129,8 @@ FlipBit
 ; IN:
 ;  A=Y
 ; OUT:
+;  $E0,E1 = 0..279 x (column)
+;  $E2    = y (row)
 ;  $26,27 = HGR1 addr
 ;  $F7,F8 = HGR2 addr
 GetHgrBaseAddr
@ -1141,8 +1143,8 @@ GetHgrBaseAddr
        LDA GBASL
        STA aux_ptr+0
        LDA GBASH
-        AND #$1F
-        ORA #$40
+        AND #$1F            ; stripe page 1
+        ORA #$40            ; set to page 2
        STA aux_ptr+1
    FIN
        RTS