From 26b1f10e1675c25b8de57bfe73b3d9c430d7fb29 Mon Sep 17 00:00:00 2001
From: Samuel Walker <swalker@piwalker.net>
Date: Fri, 30 May 2025 11:15:21 -0600
Subject: [PATCH] dma and mbc1 passing

---
 .vscode/launch.json |  2 +-
 include/cart.h      |  1 +
 lib/bus.c           |  2 ++
 lib/cart.c          | 74 +++++++++++++++++++++++++++++++++++++++------
 lib/cpu.c           | 14 +++------
 lib/dma.c           |  4 +--
 lib/ppu.c           |  2 +-
 7 files changed, 76 insertions(+), 23 deletions(-)

diff --git a/.vscode/launch.json b/.vscode/launch.json
index 9bf4f7e..2cb39d5 100644
--- a/.vscode/launch.json
+++ b/.vscode/launch.json
@@ -9,7 +9,7 @@
             "request": "launch",
             "name": "Debug",
             "program": "${workspaceFolder}/build/gbemu/Debug/gbemu.exe",
-            "args": [ "${workspaceFolder}/roms/cpu_instrs.gb" ],
+            "args": [ "C:\\Users\\piwalker\\Downloads\\mts-20240926-1737-443f6e1\\mts-20240926-1737-443f6e1\\emulator-only\\mbc1\\rom_512kb.gb" ],
             "cwd": "${workspaceFolder}"
         }
     ]
diff --git a/include/cart.h b/include/cart.h
index 245c30f..5818b55 100644
--- a/include/cart.h
+++ b/include/cart.h
@@ -24,6 +24,7 @@ typedef struct {
     u32 rom_size;
     u8 *rom_data;
     rom_header *header;
+    bool is_multicart;
 
     //mbc1 data
     bool ram_enabled;
diff --git a/lib/bus.c b/lib/bus.c
index 2043b8d..e7c136a 100644
--- a/lib/bus.c
+++ b/lib/bus.c
@@ -81,6 +81,8 @@ void bus_write(u16 address, u8 value) {
         //OAM
         if(!dma_transferring())
             ppu_oam_write(address, value);
+        else
+            printf("ACCESS DURING DMA!\n");
         return;
     } else if (address < 0xFF00) {
         //reserved unusable
diff --git a/lib/cart.c b/lib/cart.c
index 12c46d2..41e973f 100644
--- a/lib/cart.c
+++ b/lib/cart.c
@@ -250,6 +250,25 @@ bool cart_load(char *cart) {
         fprintf(stderr, "WARNING!!! The header checksum does not match! ROM may be corrupt or invalid!\n");
     }
 
+    if(cart_mbc1() && ctx.header->rom_size >= 5) {
+        int count = 0;
+        for(int i = 1; i < 4; i++) {
+            u32 start_addr = (i << 18);
+            bool same = true;
+            for(int j = 0x104; j < 0x134; j++) {
+                if(ctx.rom_data[start_addr | j] != ctx.rom_data[j]) {
+                    same = false;
+                    break;
+                }
+            }
+            if(same)
+                count++;
+        }
+        if(count >= 2) {
+            ctx.is_multicart = true;
+        }
+    }
+
     if(ctx.battery) {
         cart_battery_load();
     }
@@ -294,38 +313,66 @@ void cart_write(u16 address, u8 value){
 
     if((address & 0xE000) == 0x2000) {
         //rom bank
-        if(value == 0) {
-            value = 1;
-        }
         if(cart_mbc3()) {
             value &= 0b1111111;
+            if(value == 0) {
+                value = 1;
+            }
             ctx.rom_bank_value = value;
             ctx.rom_bank_x = ctx.rom_data + (0x4000 * ctx.rom_bank_value);
         }else {
+            //printf("Bank Value: %d\n", value);
             value &= 0b11111;
+            if(value == 0) {
+                value = 1;
+            }
+            if(ctx.is_multicart)
+                value &= 0b1111;
+            //printf("Bank Value after filter: %d\n", value);
+            switch(ctx.header->rom_size) {
+                case 0: value &= 0b1; break;
+                case 1: value &= 0b11; break;
+                case 2: value &= 0b111; break;
+                case 3: value &= 0b1111; break;
+                default: break;
+            }
             ctx.rom_bank_value = value;
             if(ctx.header->rom_size >= 5) {
                 ctx.rom_bank_x = ctx.rom_data + (0x4000 * (ctx.rom_bank_value+ctx.rom_bank_value_2));
+                //printf("(REG1 >5) Banked %d\n", ctx.rom_bank_value+ctx.rom_bank_value_2);
                 return;
             }
             ctx.rom_bank_x = ctx.rom_data + (0x4000 * ctx.rom_bank_value);
+            //printf("(REG1 <5) Banked %d\n", ctx.rom_bank_value);
         }
     }
 
     if((address & 0xE000) == 0x4000) {
         //ram bank number
-        if(cart_mbc1() && ctx.banking_mode && ctx.header->rom_size >= 5) {
+        if(cart_mbc1() && ctx.header->rom_size >= 5) {
+            if(ctx.header->rom_size == 5)
+                value &= 0b1;
             ctx.rom_bank_value_2 = (value & 0b11) << 5;
+            if(ctx.is_multicart)
+                ctx.rom_bank_value_2 = (value & 0b11) << 4;
             ctx.rom_bank_x = ctx.rom_data + (0x4000 * (ctx.rom_bank_value+ctx.rom_bank_value_2));
-            ctx.rom_bank_x2 = ctx.rom_data + (0x4000 * (ctx.rom_bank_value_2));
+            //printf("(REG2 >5) Banked %d\n", ctx.rom_bank_value+ctx.rom_bank_value_2);
+            if(ctx.banking_mode)
+                ctx.rom_bank_x2 = ctx.rom_data + (0x4000 * (ctx.rom_bank_value_2));
             return;
         }
         ctx.ram_bank_value = value & 0b11;
         if(ctx.ram_banking) {
-            if(cart_need_save) {
+            if(cart_need_save()) {
                 cart_battery_save();
             }
-            ctx.ram_bank = ctx.ram_banks[ctx.ram_bank_value];
+            if((ctx.header->ram_size == 2 && ctx.ram_bank_value == 0) || 
+                (ctx.header->ram_size == 3 && ctx.ram_bank_value < 4) ||
+                (ctx.header->ram_size == 5 && ctx.ram_bank_value < 8) ||
+                (ctx.header->ram_size == 4)) {
+                ctx.ram_bank = ctx.ram_banks[ctx.ram_bank_value];
+            }
+            
         }
     }
 
@@ -349,10 +396,17 @@ void cart_write(u16 address, u8 value){
             }
 
             if (ctx.ram_banking) {
-                if(cart_need_save) {
+                if(cart_need_save()) {
                     cart_battery_save();
                 }
-                ctx.ram_bank = ctx.ram_banks[ctx.ram_bank_value];
+                if((ctx.header->ram_size == 2 && ctx.ram_bank_value == 0) || 
+                    (ctx.header->ram_size == 3 && ctx.ram_bank_value < 4) ||
+                    (ctx.header->ram_size == 5 && ctx.ram_bank_value < 8) ||
+                    (ctx.header->ram_size == 4)) {
+                    ctx.ram_bank = ctx.ram_banks[ctx.ram_bank_value];
+                }
+            } else {
+                ctx.ram_bank = ctx.ram_banks[0];
             }
         }
     }
@@ -411,7 +465,7 @@ u8 cart_get_rom_bank() {
 }
 
 void cart_load_state(const cart_state* state){
-    ctx.ram_enabled = state->ram_enabled;
+    ctx.ram_enabled = state->ram_enabled; 
     ctx.ram_banking = state->ram_banking;
     ctx.banking_mode = state->banking_mode;
     ctx.rom_bank_value = state->rom_bank_value;
diff --git a/lib/cpu.c b/lib/cpu.c
index 27d30c6..ffc24f6 100644
--- a/lib/cpu.c
+++ b/lib/cpu.c
@@ -8,7 +8,7 @@
 #include <memory.h>
 
 cpu_context ctx = {0};
-#define CPU_DEBUG 0
+#define CPU_DEBUG 1
 #define FILE_LOG 0
 
 #if FILE_LOG == 1
@@ -54,10 +54,6 @@ static void execute() {
 }
 
 bool cpu_step() {
-
-    if(ctx.regs.pc == 0x4348) {
-        printf("made it!\n");
-    }
     
     if(!ctx.halted) {
         u16 pc = ctx.regs.pc;
@@ -81,15 +77,15 @@ bool cpu_step() {
 
         char inst[16];
         inst_to_str(&ctx, inst);
-
-        printf("%08lX - %04X: %-12s (%02X %02X %02X) A: %02X F: %s BC: %02X%02X DE: %02X%02X HL: %02X%02X SP: %04X PC: %04X\n", emu_get_context()->ticks, pc, inst, ctx.cur_opcode, bus_read(pc+1), bus_read(pc+2), ctx.regs.a, flags, ctx.regs.b, ctx.regs.c, ctx.regs.d, ctx.regs.e, ctx.regs.h, ctx.regs.l, ctx.regs.sp, ctx.regs.pc);
+        //printf("%-12s\n", inst);
+        //printf("%08lX - %04X: %-12s (%02X %02X %02X) A: %02X F: %s BC: %02X%02X DE: %02X%02X HL: %02X%02X SP: %04X PC: %04X\n", emu_get_context()->ticks, pc, inst, ctx.cur_opcode, bus_read(pc+1), bus_read(pc+2), ctx.regs.a, flags, ctx.regs.b, ctx.regs.c, ctx.regs.d, ctx.regs.e, ctx.regs.h, ctx.regs.l, ctx.regs.sp, ctx.regs.pc);
         if(ctx.cur_inst == NULL){
             printf("Unknown Instruction! %02X\n", ctx.cur_opcode);
             exit(-7);
         }
 
-        dbg_update();
-        dbg_print();
+        //dbg_update();
+        //dbg_print();
 #endif
 
         execute();
diff --git a/lib/dma.c b/lib/dma.c
index 5906434..b8da838 100644
--- a/lib/dma.c
+++ b/lib/dma.c
@@ -7,7 +7,7 @@ static dma_context ctx;
 void dma_start(u8 start) {
     ctx.active = true;
     ctx.byte = 0;
-    ctx.start_delay = 2;
+    ctx.start_delay = 0;
     ctx.value = start;
 }
 
@@ -21,7 +21,7 @@ void dma_tick() {
         return;
     }
 
-    ppu_oam_write(ctx.byte, bus_read(((ctx.value << 8)) + ctx.byte));
+    ppu_oam_write(ctx.byte, bus_read((ctx.value << 8) | ctx.byte));
 
     ctx.byte++;
 
diff --git a/lib/ppu.c b/lib/ppu.c
index c2c72fe..b1f2d76 100644
--- a/lib/ppu.c
+++ b/lib/ppu.c
@@ -70,7 +70,7 @@ void ppu_oam_write(u16 address, u8 value) {
 }
 
 u8 ppu_oam_read(u16 address){
-    if (address > 0xFE00) {
+    if (address >= 0xFE00) {
         address -= 0xFE00;
     }