working mmc3

Author: zohassadar

README.md

@@ -1,5 +1,3 @@
-Toying with MMC3 in this branch.  Only problem I'm aware of to solve is a screen flicker during initGameBackground.  May come back to this later.
-
 # TetrisGYM
 
 <div align="center">

build.sh

@@ -5,7 +5,7 @@ compile_flags=()
 help () {
     echo "Usage: $0 [-v] [-m <1|3>] [-a] [-s] [-k] [-h]"
     echo "-v  Enable verbose output"
-    echo "-m  Set mapper.  Valid values are 1 and 3.  Default 1."
+    echo "-m  Set mapper.  Valid values are 1, 3 and 4.  Default 1."
     echo "-a  Enable pressing select to end game"
     echo "-s  Disable saving of high scores"
     echo "-k  Enable Famicom Keyboard support"
@@ -17,7 +17,7 @@ while getopts "vm:askh" flag; do
     v) set -x ;;
     m)
         if ! [[ "${OPTARG}" =~ ^[134]$ ]]; then
-            echo "Valid INES_MAPPER (-m) options are 1 or 3"
+            echo "Valid INES_MAPPER (-m) options are 1, 3 or 4"
             exit 1
         fi
         compile_flags+=("-D INES_MAPPER=${OPTARG}")

src/gamemode/gametypemenu/menu.asm

@@ -18,8 +18,9 @@ gameMode_gameTypeMenu:
         jsr changeCHRBank1
 .endif
 .if INES_MAPPER = 4
+        ; Horizontal mirroring
         lda #$1
-        sta $A000
+        sta MMC3_MIRRORING
 .endif
         lda #%10011 ; used to be $10 (enable horizontal mirroring)
         jsr setMMC1Control

src/gamemodestate/initbackground.asm

@@ -47,6 +47,10 @@ gameModeState_initGameBackground:
         lda #%10011000
         sta PPUCTRL
         sta currentPpuCtrl
+.elseif INES_MAPPER = 4
+        ; Vertical mirroring (Prevents screen glitching)
+        lda #$0
+        sta MMC3_MIRRORING
 .endif
         jsr resetScroll
         jsr waitForVBlankAndEnableNmi

src/io.asm

@@ -46,6 +46,10 @@ MMC1_Control := $8000
 MMC1_CHR0   := $BFFF
 MMC1_CHR1   := $DFFF
 
+MMC3_BANK_SELECT := $8000
+MMC3_BANK_DATA := $8001
+MMC3_MIRRORING := $A000
+
 .macro RESET_MMC1
 .if INES_MAPPER = 1
         inc $8000 ; initRam

src/util/core.asm

@@ -315,13 +315,13 @@ changeCHRBank0:
         asl a
         asl a
         ldx #$00
-        stx $8000
-        sta $8001
+        stx MMC3_BANK_SELECT
+        sta MMC3_BANK_DATA
         inx
         clc
         adc #$02
-        stx $8000
-        sta $8001
+        stx MMC3_BANK_SELECT
+        sta MMC3_BANK_DATA
 .endif
         rts
 
@@ -340,23 +340,23 @@ changeCHRBank1:
         asl a
         asl a
         ldx #$02
-        stx $8000
-        sta $8001
+        stx MMC3_BANK_SELECT
+        sta MMC3_BANK_DATA
         inx
         clc
         adc #$01
-        stx $8000
-        sta $8001
+        stx MMC3_BANK_SELECT
+        sta MMC3_BANK_DATA
         inx
         clc
         adc #$01
-        stx $8000
-        sta $8001
+        stx MMC3_BANK_SELECT
+        sta MMC3_BANK_DATA
         inx
         clc
         adc #$01
-        stx $8000
-        sta $8001
+        stx MMC3_BANK_SELECT
+        sta MMC3_BANK_DATA
 .endif
         rts
 
@@ -375,12 +375,12 @@ changePRGBank:
         asl     a
         asl     a
         ldx     #$06
-        stx     $8000
-        sta     $8001
+        stx     MMC3_BANK_SELECT
+        sta     MMC3_BANK_DATA
         inx
         clc
         adc     #$01
-        stx     $8000
-        sta     $8001
+        stx     MMC3_BANK_SELECT
+        sta     MMC3_BANK_DATA
 .endif
         rts