Initial code to support SGB, command “parsing”, replacement SGB boot ROM

BootROMs/sgb_boot.asm

@@ -0,0 +1,209 @@
+; Sameboy CGB bootstrap ROM
+; Todo: use friendly names for HW registers instead of magic numbers
+SECTION "BootCode", ROM0[$0]
+Start:
+; Init stack pointer
+    ld sp, $fffe
+
+; Clear memory VRAM
+    ld hl, $8000
+
+.clearVRAMLoop
+    ldi [hl], a
+    bit 5, h
+    jr z, .clearVRAMLoop
+
+; Init Audio
+    ld a, $80
+    ldh [$26], a
+    ldh [$11], a
+    ld a, $f3
+    ldh [$12], a
+    ldh [$25], a
+    ld a, $77
+    ldh [$24], a
+
+; Init BG palette to white
+    ld a, $0
+    ldh [$47], a
+
+; Load logo from ROM.
+; A nibble represents a 4-pixels line, 2 bytes represent a 4x4 tile, scaled to 8x8.
+; Tiles are ordered left to right, top to bottom.
+    ld de, $104 ; Logo start
+    ld hl, $8010 ; This is where we load the tiles in VRAM
+
+.loadLogoLoop
+    ld a, [de] ; Read 2 rows
+    ld b, a
+    call DoubleBitsAndWriteRow
+    call DoubleBitsAndWriteRow
+    inc de
+    ld a, e
+    xor $34 ; End of logo
+    jr nz, .loadLogoLoop
+
+; Load trademark symbol
+    ld de, TrademarkSymbol
+    ld c,$08
+.loadTrademarkSymbolLoop:
+    ld a,[de]
+    inc de
+    ldi [hl],a
+    inc hl
+    dec c
+    jr nz, .loadTrademarkSymbolLoop
+
+; Set up tilemap
+    ld a,$19      ; Trademark symbol
+    ld [$9910], a ; ... put in the superscript position
+    ld hl,$992f   ; Bottom right corner of the logo
+    ld c,$c       ; Tiles in a logo row
+.tilemapLoop
+    dec a
+    jr z, .tilemapDone
+    ldd [hl], a
+    dec c
+    jr nz, .tilemapLoop
+    ld l,$0f ; Jump to top row
+    jr .tilemapLoop
+.tilemapDone
+
+    ; Turn on LCD
+    ld a, $91
+    ldh [$40], a
+
+    ld a, $f1 ; Packet magic, increases by 2 for every packet
+    ldh [$80], a
+    ld hl, $104 ; Header start
+    
+    xor a
+    ld c, a ; JOYP
+
+.sendCommand
+    xor a
+    ldh [c], a
+    ld a, $30
+    ldh [c], a
+    
+    ldh a, [$80]
+    call SendByte
+    push hl
+    ld b, $e
+    ld d, 0
+    
+.checksumLoop
+    call ReadHeaderByte
+    add d
+    ld d, a
+    dec b
+    jr nz, .checksumLoop
+    
+    ; Send checksum
+    call SendByte
+    pop hl
+    
+    ld b, $e
+.sendLoop
+    call ReadHeaderByte
+    call SendByte
+    dec b
+    jr nz, .sendLoop
+    
+    ; Done bit
+    ld a, $20
+    ldh [c], a
+    ld a, $30
+    ldh [c], a
+    
+    ; Update command
+    ldh a, [$80]
+    add 2
+    ldh [$80], a
+    
+    ld a, $58
+    cp l
+    jr nz, .sendCommand
+    
+    ; Write to sound registers for DMG compatibility
+    ld c, $13
+    ld a, $c1
+    ldh [c], a
+    inc c
+    ld a, 7
+    ldh [c], a
+    
+    ; Init BG palette
+    ld a, $fc
+    ldh [$47], a
+    
+; Set registers to match the original SGB boot
+    ld a, 1
+    ld hl, $c060
+    
+; Boot the game
+    jp BootGame
+
+ReadHeaderByte:
+    ld a, $4F
+    cp l
+    jr c, .zero
+    ld a, [hli]
+    ret
+.zero:
+    inc hl
+    xor a
+    ret
+
+SendByte:
+    ld e, a
+    ld d, 8
+.loop
+    ld a, $10
+    rr e
+    jr c, .zeroBit
+    add a ; 10 -> 20
+.zeroBit
+    ldh [c], a
+    ld a, $30
+    ldh [c], a
+    dec d
+    ret z
+    jr .loop
+
+DoubleBitsAndWriteRow:
+; Double the most significant 4 bits, b is shifted by 4
+    ld a, 4
+    ld c, 0
+.doubleCurrentBit
+    sla b
+    push af
+    rl c
+    pop af
+    rl c
+    dec a
+    jr nz, .doubleCurrentBit
+    ld a, c
+; Write as two rows
+    ldi [hl], a
+    inc hl
+    ldi [hl], a
+    inc hl
+    ret
+
+WaitFrame:
+    push hl
+    ld hl, $FF0F
+    res 0, [hl]
+.wait
+    bit 0, [hl]
+    jr z, .wait
+    pop hl
+    ret
+
+TrademarkSymbol:
+db $3c,$42,$b9,$a5,$b9,$a5,$42,$3c
+
+SECTION "BootGame", ROM0[$fe]
+BootGame:
+    ldh [$50], a

Cocoa/Document.m

@@ -16,13 +16,15 @@ enum model {
     MODEL_DMG,
     MODEL_CGB,
     MODEL_AGB,
+    MODEL_SGB,
 };
 
 static const GB_model_t cocoa_to_internal_model[] =
 {
     [MODEL_DMG] = GB_MODEL_DMG_B,
     [MODEL_CGB] = GB_MODEL_CGB_E,
-    [MODEL_AGB] = GB_MODEL_AGB
+    [MODEL_AGB] = GB_MODEL_AGB,
+    [MODEL_SGB] = GB_MODEL_SGB,
 };
 
 @interface Document ()
@@ -157,7 +159,7 @@ static void printImage(GB_gameboy_t *gb, uint32_t *image, uint8_t height,
     return [[NSBundle mainBundle] pathForResource:name ofType:@"bin"];
 }
 
-/* Todo: Unify the 3 init functions */
+/* Todo: Unify the 4 init functions */
 - (void) initDMG
 {
     current_model = MODEL_DMG;
@@ -166,6 +168,14 @@ static void printImage(GB_gameboy_t *gb, uint32_t *image, uint8_t height,
     [self initCommon];
 }
 
+- (void) initSGB
+{
+    current_model = MODEL_SGB;
+    GB_init(&gb, cocoa_to_internal_model[current_model]);
+    GB_load_boot_rom(&gb, [[self bootROMPathForName:@"sgb_boot"] UTF8String]);
+    [self initCommon];
+}
+
 - (void) initCGB
 {
     if ([[NSUserDefaults standardUserDefaults] boolForKey:@"EmulateAGB"]) {
@@ -274,7 +284,7 @@ static void printImage(GB_gameboy_t *gb, uint32_t *image, uint8_t height,
         current_model = (enum model)[sender tag];
     }
     
-    static NSString * const boot_names[] = {@"dmg_boot", @"cgb_boot", @"agb_boot"};
+    static NSString * const boot_names[] = {@"dmg_boot", @"cgb_boot", @"agb_boot", @"sgb_boot"};
     GB_load_boot_rom(&gb, [[self bootROMPathForName:boot_names[current_model - 1]] UTF8String]);
 
     if ([sender tag] == MODEL_NONE) {
@@ -287,7 +297,8 @@ static void printImage(GB_gameboy_t *gb, uint32_t *image, uint8_t height,
     if ([sender tag] != 0) {
         /* User explictly selected a model, save the preference */
         [[NSUserDefaults standardUserDefaults] setBool:current_model == MODEL_DMG forKey:@"EmulateDMG"];
-        [[NSUserDefaults standardUserDefaults] setBool:current_model== MODEL_AGB forKey:@"EmulateAGB"];
+        [[NSUserDefaults standardUserDefaults] setBool:current_model == MODEL_SGB forKey:@"EmulateSGB"];
+        [[NSUserDefaults standardUserDefaults] setBool:current_model == MODEL_AGB forKey:@"EmulateAGB"];
     }
     
     /* Reload the ROM, SAV and SYM files */
@@ -382,6 +393,9 @@ static void printImage(GB_gameboy_t *gb, uint32_t *image, uint8_t height,
     if ([[NSUserDefaults standardUserDefaults] boolForKey:@"EmulateDMG"]) {
         [self initDMG];
     }
+    else if ([[NSUserDefaults standardUserDefaults] boolForKey:@"EmulateSGB"]) {
+        [self initSGB];
+    }
     else {
         [self initCGB];
     }

Cocoa/MainMenu.xib

@@ -1,7 +1,8 @@
-<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<?xml version="1.0" encoding="UTF-8"?>
-<document type="com.apple.InterfaceBuilder3.Cocoa.XIB" version="3.0" toolsVersion="9531" systemVersion="14F1713" targetRuntime="MacOSX.Cocoa" propertyAccessControl="none" useAutolayout="YES" customObjectInstantitationMethod="direct">
+<document type="com.apple.InterfaceBuilder3.Cocoa.XIB" version="3.0" toolsVersion="13771" targetRuntime="MacOSX.Cocoa" propertyAccessControl="none" useAutolayout="YES" customObjectInstantitationMethod="direct">
     <dependencies>
-        <plugIn identifier="com.apple.InterfaceBuilder.CocoaPlugin" version="9531"/>
+        <deployment identifier="macosx"/>
+        <plugIn identifier="com.apple.InterfaceBuilder.CocoaPlugin" version="13771"/>
     </dependencies>
     <objects>
         <customObject id="-2" userLabel="File's Owner" customClass="NSApplication">
@@ -311,7 +312,13 @@
                                 </menu>
                             </menuItem>
                             <menuItem isSeparatorItem="YES" id="5GS-tt-E0a"/>
-                            <menuItem title="Game Boy" tag="1" id="vc7-yy-ARW">
+                            <menuItem title="Game Boy" tag="1" id="g7C-LA-VAr">
+                                <modifierMask key="keyEquivalentModifierMask"/>
+                                <connections>
+                                    <action selector="reset:" target="-1" id="rxG-cz-s1S"/>
+                                </connections>
+                            </menuItem>
+                            <menuItem title="Super Game Boy" tag="4" id="vc7-yy-ARW">
                                 <modifierMask key="keyEquivalentModifierMask"/>
                                 <connections>
                                     <action selector="reset:" target="-1" id="E4M-QG-ua9"/>

Core/gb.c

@@ -506,7 +506,12 @@ bool GB_is_inited(GB_gameboy_t *gb)
 
 bool GB_is_cgb(GB_gameboy_t *gb)
 {
-    return ((gb->model) & GB_MODEL_FAMILY_MASK) == GB_MODEL_CGB_FAMILY;
+    return (gb->model & GB_MODEL_FAMILY_MASK) == GB_MODEL_CGB_FAMILY;
+}
+
+bool GB_is_sgb(GB_gameboy_t *gb)
+{
+    return (gb->model & ~GB_MODEL_PAL_BIT) == GB_MODEL_SGB || gb->model == GB_MODEL_SGB2;
 }
 
 void GB_set_turbo_mode(GB_gameboy_t *gb, bool on, bool no_frame_skip)
@@ -541,6 +546,8 @@ static void reset_ram(GB_gameboy_t *gb)
             break;
             
         case GB_MODEL_DMG_B:
+        case GB_MODEL_SGB_NTSC: /* Unverified*/
+        case GB_MODEL_SGB_PAL: /* Unverified */
             for (unsigned i = 0; i < gb->ram_size; i++) {
                 gb->ram[i] = (random() & 0xFF);
                 if (i & 0x100) {
@@ -551,15 +558,13 @@ static void reset_ram(GB_gameboy_t *gb)
                 }
             }
             break;
-#if 0
+            
-        /* Not emulated yet, for documentation only */
         case GB_MODEL_SGB2:
             for (unsigned i = 0; i < gb->ram_size; i++) {
                 gb->ram[i] = 0x55;
                 gb->ram[i] ^= random() & random() & random();
             }
             break;
-#endif
         
         case GB_MODEL_CGB_C:
             for (unsigned i = 0; i < gb->ram_size; i++) {
@@ -729,5 +734,11 @@ void GB_set_clock_multiplier(GB_gameboy_t *gb, double multiplier)
 
 uint32_t GB_get_clock_rate(GB_gameboy_t *gb)
 {
+    if (gb->model == GB_MODEL_SGB_NTSC) {
+        return SGB_NTSC_FREQUENCY * gb->clock_multiplier;
+    }
+    if (gb->model == GB_MODEL_SGB_PAL) {
+        return SGB_PAL_FREQUENCY * gb->clock_multiplier;
+    }
     return CPU_FREQUENCY * gb->clock_multiplier;
 }

Core/gb.h

@@ -19,6 +19,7 @@
 #include "rewind.h"
 #include "z80_cpu.h"
 #include "symbol_hash.h"
+#include "sgb.h"
 
 #define GB_STRUCT_VERSION 13
 
@@ -27,6 +28,7 @@
 #define GB_MODEL_DMG_FAMILY 0x000
 #define GB_MODEL_MGB_FAMILY 0x100
 #define GB_MODEL_CGB_FAMILY 0x200
+#define GB_MODEL_PAL_BIT 0x1000
 #endif
 
 #if __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
@@ -48,15 +50,18 @@ typedef union {
     uint8_t data[5];
 } GB_rtc_time_t;
 
+
 typedef enum {
 
     // GB_MODEL_DMG_0 = 0x000,
     // GB_MODEL_DMG_A = 0x001,
     GB_MODEL_DMG_B = 0x002,
     // GB_MODEL_DMG_C = 0x003,
-    // GB_MODEL_SGB = 0x004,
+    GB_MODEL_SGB = 0x004,
+    GB_MODEL_SGB_NTSC = GB_MODEL_SGB,
+    GB_MODEL_SGB_PAL = 0x1004,
     // GB_MODEL_MGB = 0x100,
-    // GB_MODEL_SGB2 = 0x101,
+    GB_MODEL_SGB2 = 0x101,
     // GB_MODEL_CGB_0 = 0x200,
     // GB_MODEL_CGB_A = 0x201,
     // GB_MODEL_CGB_B = 0x202,
@@ -203,6 +208,8 @@ typedef enum {
 #ifdef GB_INTERNAL
 #define LCDC_PERIOD 70224
 #define CPU_FREQUENCY 0x400000
+#define SGB_NTSC_FREQUENCY (21477272 / 5)
+#define SGB_PAL_FREQUENCY (21281370 / 5)
 #define DIV_CYCLES (0x100)
 #define INTERNAL_DIV_CYCLES (0x40000)
 
@@ -460,6 +467,14 @@ struct GB_gameboy_internal_s {
         bool lyc_interrupt_line;
     );
     
+    /* Super Game Boy state, only dumped/loaded for relevant models */
+    GB_SECTION(sgb,
+        uint8_t sgb_command[16];
+        uint8_t sgb_command_write_index;
+        bool sgb_ready_for_pulse;
+        bool sgb_ready_for_write;
+    );
+
     /* Unsaved data. This includes all pointers, as well as everything that shouldn't be on a save state */
     /* This data is reserved on reset and must come last in the struct */
     GB_SECTION(unsaved,
@@ -584,6 +599,7 @@ __attribute__((__format__ (__printf__, fmtarg, firstvararg)))
 void GB_init(GB_gameboy_t *gb, GB_model_t model);
 bool GB_is_inited(GB_gameboy_t *gb);
 bool GB_is_cgb(GB_gameboy_t *gb);
+bool GB_is_sgb(GB_gameboy_t *gb);
 GB_model_t GB_get_model(GB_gameboy_t *gb);
 void GB_free(GB_gameboy_t *gb);
 void GB_reset(GB_gameboy_t *gb);

Core/joypad.c

@@ -47,12 +47,14 @@ void GB_update_joyp(GB_gameboy_t *gb)
         default:
             break;
     }
+    
     if (previous_state != (gb->io_registers[GB_IO_JOYP] & 0xF)) {
         /* The joypad interrupt DOES occur on CGB (Tested on CGB-CPU-06), unlike what some documents say. */
         gb->io_registers[GB_IO_IF] |= 0x10;
         gb->stopped = false;
     }
-    gb->io_registers[GB_IO_JOYP] |= 0xC0; // No SGB support
+    
+    gb->io_registers[GB_IO_JOYP] |= 0xC0;
 }
 
 void GB_set_key_state(GB_gameboy_t *gb, GB_key_t index, bool pressed)

Core/memory.c

@@ -271,6 +271,9 @@ static uint8_t read_high_memory(GB_gameboy_t *gb, uint16_t addr)
                 return gb->extra_oam[addr - 0xfea0];
                 
             case GB_MODEL_DMG_B:
+            case GB_MODEL_SGB_NTSC:
+            case GB_MODEL_SGB_PAL:
+            case GB_MODEL_SGB2:
                 ;
         }
     }
@@ -575,6 +578,9 @@ static void write_high_memory(GB_gameboy_t *gb, uint16_t addr, uint8_t value)
                     gb->extra_oam[addr - 0xfea0] = value;
                     break;
                 case GB_MODEL_DMG_B:
+                case GB_MODEL_SGB_NTSC:
+                case GB_MODEL_SGB_PAL:
+                case GB_MODEL_SGB2:
                 case GB_MODEL_CGB_E:
                 case GB_MODEL_AGB:
                     break;
@@ -727,6 +733,7 @@ static void write_high_memory(GB_gameboy_t *gb, uint16_t addr, uint8_t value)
                 gb->io_registers[GB_IO_JOYP] &= 0x0F;
                 gb->io_registers[GB_IO_JOYP] |= value & 0xF0;
                 GB_update_joyp(gb);
+                GB_sgb_write(gb, value);
                 return;
 
             case GB_IO_BIOS:

Core/sgb.c

@@ -0,0 +1,51 @@
+#include "sgb.h"
+
+void GB_sgb_write(GB_gameboy_t *gb, uint8_t value)
+{
+    if (!GB_is_sgb(gb)) return;
+    switch ((value >> 4) & 3 ) {
+        case 3:
+            gb->sgb_ready_for_pulse = true;
+            break;
+            
+        case 2: // Zero
+            if (!gb->sgb_ready_for_pulse || !gb->sgb_ready_for_write) return;
+            if (gb->sgb_command_write_index >= sizeof(gb->sgb_command) * 8) {
+                GB_log(gb, "Got SGB command: ");
+                for (unsigned i = 0; i < 16; i++) {
+                    GB_log(gb, "%02x ", gb->sgb_command[i]);
+                }
+                GB_log(gb, "\n");
+                gb->sgb_ready_for_pulse = false;
+                gb->sgb_ready_for_write = false;
+            }
+            else {
+                gb->sgb_command_write_index++;
+                gb->sgb_ready_for_pulse = false;
+            }
+            break;
+        case 1: // One
+            if (!gb->sgb_ready_for_pulse || !gb->sgb_ready_for_write) return;
+            if (gb->sgb_command_write_index >= sizeof(gb->sgb_command) * 8) {
+                GB_log(gb, "Corrupt SGB command.\n");
+                gb->sgb_ready_for_pulse = false;
+                gb->sgb_ready_for_write = false;
+            }
+            else {
+                gb->sgb_command[gb->sgb_command_write_index / 8] |= 1 << (gb->sgb_command_write_index & 7);
+                gb->sgb_command_write_index++;
+                gb->sgb_ready_for_pulse = false;
+            }
+            break;
+        
+        case 0:
+            gb->sgb_ready_for_pulse = false;
+            gb->sgb_ready_for_write = true;
+            gb->sgb_command_write_index = 0;
+            memset(gb->sgb_command, 0, sizeof(gb->sgb_command));
+            break;
+            
+        default:
+            break;
+    }
+}

Core/sgb.h

@@ -0,0 +1,9 @@
+#ifndef sgb_h
+#define sgb_h
+#include "gb.h"
+
+#ifdef GB_INTERNAL
+void GB_sgb_write(GB_gameboy_t *gb, uint8_t value);
+#endif
+
+#endif

Makefile

@@ -106,9 +106,9 @@ endif
 
 cocoa: $(BIN)/SameBoy.app
 quicklook: $(BIN)/SameBoy.qlgenerator
-sdl: $(SDL_TARGET) $(BIN)/SDL/dmg_boot.bin $(BIN)/SDL/cgb_boot.bin $(BIN)/SDL/agb_boot.bin $(BIN)/SDL/LICENSE $(BIN)/SDL/registers.sym $(BIN)/SDL/background.bmp $(BIN)/SDL/Shaders
+sdl: $(SDL_TARGET) $(BIN)/SDL/dmg_boot.bin $(BIN)/SDL/cgb_boot.bin $(BIN)/SDL/agb_boot.bin $(BIN)/SDL/sgb_boot.bin $(BIN)/SDL/LICENSE $(BIN)/SDL/registers.sym $(BIN)/SDL/background.bmp $(BIN)/SDL/Shaders
-bootroms: $(BIN)/BootROMs/agb_boot.bin $(BIN)/BootROMs/cgb_boot.bin $(BIN)/BootROMs/dmg_boot.bin
+bootroms: $(BIN)/BootROMs/agb_boot.bin $(BIN)/BootROMs/cgb_boot.bin $(BIN)/BootROMs/dmg_boot.bin $(BIN)/BootROMs/sgb_boot.bin
-tester: $(TESTER_TARGET) $(BIN)/tester/dmg_boot.bin $(BIN)/tester/cgb_boot.bin $(BIN)/tester/agb_boot.bin
+tester: $(TESTER_TARGET) $(BIN)/tester/dmg_boot.bin $(BIN)/tester/cgb_boot.bin $(BIN)/tester/agb_boot.bin $(BIN)/tester/sgb_boot.bin
 all: cocoa sdl tester libretro
 
 # Get a list of our source files and their respective object file targets
@@ -180,6 +180,7 @@ $(BIN)/SameBoy.app: $(BIN)/SameBoy.app/Contents/MacOS/SameBoy \
                     $(BIN)/SameBoy.app/Contents/Resources/dmg_boot.bin \
                     $(BIN)/SameBoy.app/Contents/Resources/cgb_boot.bin \
                     $(BIN)/SameBoy.app/Contents/Resources/agb_boot.bin \
+                    $(BIN)/SameBoy.app/Contents/Resources/sgb_boot.bin \
                     $(patsubst %.xib,%.nib,$(addprefix $(BIN)/SameBoy.app/Contents/Resources/Base.lproj/,$(shell cd Cocoa;ls *.xib))) \
                     $(BIN)/SameBoy.qlgenerator \
                     Shaders
@@ -307,7 +308,7 @@ $(BIN)/BootROMs/%.bin: BootROMs/%.asm
 	-@$(MKDIR) -p $(dir $@)
 	cd BootROMs && rgbasm -o ../$@.tmp ../$<
 	rgblink -o $@.tmp2 $@.tmp
-	head -c $(if $(findstring dmg,$@), 256, 2304) $@.tmp2 > $@
+	head -c $(if $(findstring dmg,$@)$(findstring sgb,$@), 256, 2304) $@.tmp2 > $@
 	@rm $@.tmp $@.tmp2
 
 # Libretro Core (uses its own build system)