autodetect mmc1 or cnrom

Author: zohassadar

README.md

@@ -451,3 +451,4 @@ This project descends from the TAUS disassembly of NES Tetris and has been heavi
 
 * [https://github.com/ejona86/taus](https://github.com/ejona86/taus)  
 * [https://github.com/CelestialAmber/TetrisNESDisasm](https://github.com/CelestialAmber/TetrisNESDisasm)  
+* [https://github.com/pinobatch/holy-mapperel](https://github.com/pinobatch/holy-mapperel)

build.js

@@ -6,21 +6,22 @@ const { spawnSync } = require('child_process');
 console.log('TetrisGYM buildscript');
 console.time('build');
 
-const mappers = [1, 3, 4, 5];
+const mappers = [0, 1, 3, 4, 5];
 
 // options handling
 
 const args = process.argv.slice(2);
 
 if (args.includes('-h')) {
-    console.log(`usage: node build.js [-h] [-v] [-m<${mappers.join('|')}>] [-a] [-s] [-k] [-w]
+    console.log(`usage: node build.js [-h] [-v] [-m<${mappers.join('|')}>] [-a] [-s] [-k] [-w] [-c] [-o]
 
 -m  mapper
 -a  faster aeppoz + press select to end game
 -s  disable highscores/SRAM
 -k  Famicom Keyboard support
 -w  force WASM compiler
 -c  force PNG to CHR conversion
+-o  override autodetect mmc1 header with cnrom
 -h  you are here
 `);
     process.exit(0);
@@ -42,7 +43,7 @@ console.log(`using ${nativeCC65 ? 'system' : 'wasm'} ca65/ld65`);
 
 // mapper options
 
-const mapper = args.find((d) => d.startsWith('-m'))?.slice(2) ?? 1;
+const mapper = args.find((d) => d.startsWith('-m'))?.slice(2) ?? 0;
 
 if (!mappers.includes(+mapper)) {
     console.error(
@@ -74,6 +75,11 @@ if (args.includes('-s')) {
     console.log('highscore saving disabled');
 }
 
+if (args.includes('-o')) {
+    compileFlags.push('-D', 'CNROM_OVERRIDE=1');
+    console.log('cnrom override for autodetect');
+}
+
 console.log();
 
 // build / compress nametables

src/boot.asm

@@ -1,14 +1,4 @@
-        ldy #$06
-        sty tmp2
-        ldy #$00
-        sty tmp1
-        lda #$00
-@zeroOutPages:
-        sta (tmp1),y
-        dey
-        bne @zeroOutPages
-        dec tmp2
-        bpl @zeroOutPages
+        ; $0000 through $06FF cleared during vblank wait
         lda initMagic
         cmp #$54
         bne @coldBoot

src/constants.asm

@@ -1,5 +1,5 @@
 .ifndef INES_MAPPER ; is set via ca65 flags
-INES_MAPPER := 1 ; supports 1, 3 and 4 (MMC1 / CNROM / MMC3)
+INES_MAPPER := 0 ; supports 0 (autodetect 1/3), 1, 3, 4 and 5 (MMC1 / CNROM / MMC3 / MMC5)
 .endif
 
 HAS_MMC = INES_MAPPER = 1 || INES_MAPPER = 4 || INES_MAPPER = 5
@@ -17,6 +17,10 @@ AUTO_WIN := 0
 KEYBOARD := 0
 .endif
 
+.ifndef CNROM_OVERRIDE
+CNROM_OVERRIDE := 0
+.endif
+
 NO_MUSIC := 1
 
 ; dev flags

src/header.asm

@@ -12,9 +12,20 @@
 INES_MIRROR = 0 ; 0 = horizontal mirroring, 1 = vertical mirroring (ignored in MMC1)
 INES_SRAM   = 1 ; 1 = battery backed SRAM at $6000-7FFF
 
+; Override INES_MAPPER for mode 0 (auto detect)
+.if INES_MAPPER = 0
+    .if CNROM_OVERRIDE
+    _INES_MAPPER = 3 ; Test CNROM on Emulator/Flashcart
+    .else
+    _INES_MAPPER = 1 ; MMC1 for Emulator/Flashcart
+    .endif
+.else
+_INES_MAPPER = INES_MAPPER ; use actual INES_MAPPER otherwise
+.endif
+
 .byte 'N', 'E', 'S', $1A ; ID
 .byte $02 ; 16k PRG chunk count
 .byte $02 ; 8k CHR chunk count
-.byte INES_MIRROR | (INES_SRAM << 1) | ((INES_MAPPER & $f) << 4)
-.byte (INES_MAPPER & %11110000)
+.byte INES_MIRROR | (INES_SRAM << 1) | ((_INES_MAPPER & $f) << 4)
+.byte (_INES_MAPPER & %11110000)
 .byte $0, $0, $0, $0, $0, $0, $0, $0 ; padding

src/main.asm

@@ -54,6 +54,10 @@ mainLoop:
 .include "util/math.asm"
 .include "util/menuthrottle.asm"
 .include "util/modetext.asm"
+.include "util/mapper.asm"
+.if INES_MAPPER = 0
+.include "util/autodetect.asm"
+.endif
 
 .include "sprites/loadsprite.asm"
 .include "sprites/drawrect.asm"

src/ram.asm

@@ -210,7 +210,9 @@ dasOnlyShiftDisabled: .res 1 ; $63A
 
 invisibleFlag: .res 1 ; $63B  ; 0 for normal mode, non-zero for Invisible playfield rendering.  Reset on game init and game over.
 
-    .res $39
+mapperId: .res 1 ; $63C ; For INES_MAPPER 0 (autodetect).  0 = CNROM.  1 = MMC1.  
+
+    .res $38
 
 .if KEYBOARD
 newlyPressedKeys: .res 1 ; $0675

src/reset.asm

@@ -4,31 +4,60 @@ reset:  cld
         ldx #$00
         stx PPUCTRL
         stx PPUMASK
+
+        ; init code from https://www.nesdev.org/wiki/Init_code
+        bit PPUSTATUS
 @vsyncWait1:
-        lda PPUSTATUS
+        bit PPUSTATUS
         bpl @vsyncWait1
+
+        ; zero out pages 0 through 6 while waiting
+        txa
+@clrmem:
+        sta $0000,x
+        sta $0100,x
+        sta $0200,x
+        sta $0300,x
+        sta $0400,x
+        sta $0500,x
+        sta $0600,x
+        inx
+        bne @clrmem
+
+        bit PPUSTATUS
 @vsyncWait2:
-        lda PPUSTATUS
+        bit PPUSTATUS
         bpl @vsyncWait2
-        dex
+
+        dex ; $FF for stack pointer
         txs
-.if INES_MAPPER = 1
-        RESET_MMC1
-.elseif INES_MAPPER = 4 
-        jsr mmc3Init
-.elseif INES_MAPPER = 5
-        jsr mmc5Init
-.endif
+        jsr changePRGBank ; 0 in accumulator
+        jsr mapperInit
         jsr setVerticalMirroring
         lda #CHRBankSet0
         jsr changeCHRBanks
-        lda #$00
-        jsr changePRGBank
         jmp initRam
 
-.if INES_MAPPER = 4
+mapperInit:
+; autodetect
+.if INES_MAPPER = 0
+        jsr testHorizontalMirroring
+        bne not_mmc1
+        jsr testVerticalMirroring
+        bne not_mmc1
+        inc mapperId ; 1 for MMC1, otherwise 0 for CNROM
+not_mmc1:
+
+; MMC1
+.elseif INES_MAPPER = 1
+        RESET_MMC1
+
+; CNROM (no init)
+.elseif INES_MAPPER = 3
+
+; MMC3
+.elseif INES_MAPPER = 4
 ; https://www.nesdev.org/wiki/MMC3
-mmc3Init:
         ; 110: R6: Select 8 KB PRG ROM bank at $8000-$9FFF (or $C000-$DFFF)
         ldx     #$06
         ldy     #$00
@@ -43,18 +72,19 @@ mmc3Init:
         lda     #$80 ; enable PRG RAM
         sta     MMC3_PRG_RAM
         rts
+
+; MMC5
 .elseif INES_MAPPER = 5
 ; https://www.nesdev.org/wiki/MMC5
-mmc5Init:
         ldx #$00
         stx MMC5_PRG_MODE ; 0: 1 32Kb bank
         inx
         stx MMC5_CHR_MODE ; 1: 4kb CHR pages
         stx MMC5_RAM_PROTECT2 ; 1: enable PRG RAM
         inx
         stx MMC5_RAM_PROTECT1 ; 2: enable PRG RAM
-        rts
 .endif
+        rts
 
 
 MMC1_PRG:

src/util/autodetect.asm

@@ -0,0 +1,77 @@
+; Mapper detect code by pinobatch.   Only relevant code has been copied and has been modified.
+; Original code: https://github.com/pinobatch/holy-mapperel/blob/60ea5c0d97dedca1522525b054012b7c8526f1e1/src/mapper_detect.s
+
+; Original notice:
+
+; Mapper detection for Holy Mapperel
+;
+; Copyright 2013-2017 Damian Yerrick
+; 
+; This software is provided 'as-is', without any express or implied
+; warranty.  In no event will the authors be held liable for any damages
+; arising from the use of this software.
+; 
+; Permission is granted to anyone to use this software for any purpose,
+; including commercial applications, and to alter it and redistribute it
+; freely, subject to the following restrictions:
+; 
+; 1. The origin of this software must not be misrepresented; you must not
+;    claim that you wrote the original software. If you use this software
+;    in a product, an acknowledgment in the product documentation would be
+;    appreciated but is not required.
+; 2. Altered source versions must be plainly marked as such, and must not be
+;    misrepresented as being the original software.
+; 3. This notice may not be removed or altered from any source distribution.
+;
+
+MIRRPROBE_V = %0101
+MIRRPROBE_H = %0011
+
+testHorizontalMirroring:
+        inc mapperId
+        jsr setHorizontalMirroring
+        dec mapperId
+        jsr testMirroring
+        cmp #MIRRPROBE_H
+        rts
+
+testVerticalMirroring:
+        inc mapperId
+        jsr setVerticalMirroring
+        dec mapperId
+        jsr testMirroring
+        cmp #MIRRPROBE_V
+        rts
+
+testMirroring:
+; write_mirror_probe_vals
+        ldx #$20
+        ldy #$00
+        stx PPUADDR
+        sty PPUADDR
+        sty PPUDATA
+        ldx #$2C
+        stx PPUADDR
+        sty PPUADDR
+        iny
+        sty PPUDATA
+
+; read_mirror_probe_vals
+        ldx #$20  ; src address high
+        ldy #$00  ; src address low
+        lda #$10  ; ring counter loop: finish once the 1 gets rotated out
+readloop:
+        pha
+        stx PPUADDR
+        inx
+        sty PPUADDR
+        inx
+        bit PPUDATA
+        inx
+        lda PPUDATA
+        inx
+        lsr a
+        pla
+        rol a
+        bcc readloop
+        rts