Move states to global variables

.gitignore

@@ -154,3 +154,4 @@ environment_run.ps1.env
 environment_run.sh.env
 
 # End of https://www.toptal.com/developers/gitignore/api/cmake,clion,conan
+/test_roms/

cpu/cpu.c

@@ -11,7 +11,7 @@
 /*
  * =====================================================================================
  *
- *       Filename:  cpu.c
+ *       Filename:  cpu_state.c
  *
  *    Description:  6502 CPU emulator 
  *
@@ -26,133 +26,147 @@
  * =====================================================================================
  */
 
-void cpu_init(CPU *cpu) {
+CPU cpu_state;
-    cpu->program_counter = 0x8000;
+
-    cpu->stack_pointer = 0xfd;
+void cpu_init() {
-    cpu->accumulator = 0x00;
+    cpu_state.program_counter = 0x8000;
-    cpu->x = 0x00;
+    cpu_state.stack_pointer = 0xfd;
-    cpu->y = 0x00;
+    cpu_state.accumulator = 0x00;
-    cpu->status = 0x04;
+    cpu_state.x = 0x00;
-    cpu->oam_dma_triggered = false;
+    cpu_state.y = 0x00;
-    cpu->nmi_requested = false;
+    cpu_state.status = 0x04;
+    cpu_state.oam_dma_triggered = false;
+    cpu_state.nmi_requested = false;
 }
 
-void print_registers(CPU cpu, byte op, unsigned long cycle_count) {
+void print_registers(byte op, unsigned long cycle_count) {
-    log_debug("%#02x %#02x %s \t A:%#02x X:%#02x Y:%#02x F:%#02x SP:%#02x \t [%d]",
+    log_info("%#02x %#02x %s \t A:%#02x X:%#02x Y:%#02x F:%#02x SP:%#02x \t [%d]",
-              cpu.program_counter,
+              cpu_state.program_counter,
               op,
               get_op_code_name(op),
-              cpu.accumulator,
+              cpu_state.accumulator,
-              cpu.x,
+              cpu_state.x,
-              cpu.y,
+              cpu_state.y,
-              cpu.status,
+              cpu_state.status,
-              cpu.stack_pointer,
+              cpu_state.stack_pointer,
               cycle_count);
 }
 
-void cpu_process_nmi(System *system) {
+void cpu_process_nmi() {
-    cpu_stack_push_context(system);
+    cpu_stack_push_context();
 
-    address handler_addr = mem_get_word(system, 0xfffa);
+    address handler_addr = mem_get_word(0xfffa);
     log_debug("NMI %#04x", handler_addr);
 
-    system->cpu.nmi_requested = false;
+    cpu_state.nmi_requested = false;
-    system->cpu.program_counter = handler_addr;
+    cpu_state.program_counter = handler_addr;
 }
 
-void oam_dma_upload(System *system) {
+void oam_dma_upload() {
-    byte page_high_addr = *system->ppu.oam_dma_register;
+    byte page_high_addr = *ppu_get_state()->oam_dma_register;    // TODO
     address page_addr = ((address) page_high_addr) << 8;
     byte n = 0xff;
 
-    byte *ram_source = &system->ram[page_addr];
+    byte *ram_source = mem_get_ptr(page_addr);
-    byte *oam_destination = system->ppu.oam;
+    byte *oam_destination = ppu_get_state()->oam;
 
     memcpy(oam_destination, ram_source, n);
 
     log_debug("OAM DMA %#04x", page_addr);
-    cpu_add_cycles(system, 513);    // TODO
+    cpu_add_cycles(513);    // TODO
 }
 
-void cpu_cycle(System *system) {
+void cpu_cycle() {
-    if (system->cpu.nmi_requested) {
+    if (cpu_state.nmi_requested) {
-        cpu_process_nmi(system);
+        cpu_process_nmi();
     }
 
-    if (system->cpu.oam_dma_triggered) {
+    if (cpu_state.oam_dma_triggered) {
-        oam_dma_upload(system);
+        oam_dma_upload();
-        system->cpu.oam_dma_triggered = false;
+        cpu_state.oam_dma_triggered = false;
         return;
     }
 
-    CPU cpu = system->cpu;
+    CPU cpu = cpu_state;
-    byte op = cpu_get_next_byte(system);
+    byte op = cpu_get_next_byte();
 
-    print_registers(cpu, op, system->cycle_count);
+    print_registers(op, system_get_cycles());
 
-    process_op_code(system, op);
+    process_op_code(op);
 }
 
-void cpu_add_cycles(System *system, unsigned int cycle_count) {
+void cpu_add_cycles(unsigned int cycle_count) {
-    system->cycle_count += cycle_count;
+    system_add_cycles(cycle_count);
 }
 
 // === Registers ===
-bool system_get_flag(System *system, byte mask) {
+bool cpu_get_flag(byte mask) {
-    return cpu_get_flag(&system->cpu, mask);
+    return cpu_state.status & mask;
 }
 
-void system_set_flag(System *system, byte mask, bool set) {
+void cpu_set_flag(byte mask, bool set) {
     if (set) {
-        system->cpu.status |= mask;
+        cpu_state.status |= mask;
     } else {
-        system->cpu.status &= ~mask;
+        cpu_state.status &= ~mask;
     }
 }
 
-byte cpu_get_next_byte(System *system) {
+byte cpu_get_next_byte() {
-    byte next_byte = mem_get_byte(system, system->cpu.program_counter);
+    byte next_byte = mem_get_byte(cpu_state.program_counter);
-    system->cpu.program_counter++;
+    cpu_state.program_counter++;
     return next_byte;
 }
 
-word cpu_get_next_word(System *system) {
+word cpu_get_next_word() {
-    word next_word = mem_get_word(system, system->cpu.program_counter);
+    word next_word = mem_get_word(cpu_state.program_counter);
-    system->cpu.program_counter += 2;
+    cpu_state.program_counter += 2;
     return next_word;
 }
 
-void cpu_stack_push(System *system, byte value) {
+void cpu_stack_push(byte value) {
-    assert(system->cpu.stack_pointer > 0);
+    assert(cpu_state.stack_pointer > 0);
 
-    address mem_addr = CPU_STACK_ADDR | system->cpu.stack_pointer;
+    address mem_addr = CPU_STACK_ADDR | cpu_state.stack_pointer;
-    mem_set_byte(system, mem_addr, value);
+    mem_set_byte(mem_addr, value);
-    system->cpu.stack_pointer--;
+    cpu_state.stack_pointer--;
 }
 
-byte cpu_stack_pop(System *system) {
+byte cpu_stack_pop() {
-    assert(system->cpu.stack_pointer < 0xff);
+    assert(cpu_state.stack_pointer < 0xff);
 
-    system->cpu.stack_pointer++;
+    cpu_state.stack_pointer++;
-    address mem_addr = CPU_STACK_ADDR | system->cpu.stack_pointer;
+    address mem_addr = CPU_STACK_ADDR | cpu_state.stack_pointer;
-    byte value = mem_get_byte(system, mem_addr);
+    byte value = mem_get_byte(mem_addr);
     return value;
 }
 
-void cpu_stack_push_context(System *system) {
+void cpu_stack_push_context() {
-    cpu_stack_push(system, system->cpu.program_counter >> 8);
+    cpu_stack_push(cpu_state.program_counter >> 8);
-    cpu_stack_push(system, system->cpu.program_counter & 0xff);
+    cpu_stack_push(cpu_state.program_counter & 0xff);
-    cpu_stack_push(system, system->cpu.status);
+    cpu_stack_push(cpu_state.status);
 }
 
-void cpu_stack_pop_context(System *system) {
+void cpu_stack_pop_context() {
-    byte value = cpu_stack_pop(system);
+    byte value = cpu_stack_pop();
     value &= 0xef;  // The B mask cannot be set as it is a CPU signal
     value |= 0x20;  // This value is always set
-    system->cpu.status = value;
+    cpu_state.status = value;
 
-    byte lo = cpu_stack_pop(system);
+    byte lo = cpu_stack_pop();
-    address pc = cpu_stack_pop(system) << 8;
+    address pc = cpu_stack_pop() << 8;
     pc += lo;
-    system->cpu.program_counter = pc;
+    cpu_state.program_counter = pc;
+}
+
+void cpu_trigger_oam_dma() {
+    cpu_state.oam_dma_triggered = true;
+}
+
+void cpu_trigger_nmi() {
+    cpu_state.nmi_requested = true;
+}
+
+CPU *cpu_get_state() {
+    return &cpu_state;
 }

cpu/cpu.h

@@ -19,6 +19,20 @@
 
 #define CPU_STACK_ADDR 0x0100
 
+// Reference: https://www.nesdev.org/obelisk-6502-guide/registers.html
+typedef struct cpu {
+    address program_counter;
+    byte stack_pointer;
+    byte accumulator;
+    byte x;
+    byte y;
+    byte status;
+    bool oam_dma_triggered;
+    bool nmi_requested;
+} CPU;
+
+CPU *cpu_get_state();
+
 /**
  * Gets a flag from the CPU registers.
  * 
@@ -26,11 +40,7 @@
  * @param mask The flag mask
  * @return The value of the flag.
  */
-bool system_get_flag(System *system, byte mask);
+bool cpu_get_flag(byte mask);
-
-static inline bool cpu_get_flag(CPU *cpu, byte mask) {
-    return cpu->status & mask;
-}
 
 /**
  * Sets a flag in the CPU registers.
@@ -39,7 +49,7 @@ static inline bool cpu_get_flag(CPU *cpu, byte mask) {
  * @param mask The flag mask
  * @param set If the flag is set or not
  */
-void system_set_flag(System *system, byte mask, bool set);
+void cpu_set_flag(byte mask, bool set);
 
 /**
  * Gets the next byte in the program.
@@ -48,7 +58,7 @@ void system_set_flag(System *system, byte mask, bool set);
  * @param system The system 
  * @return The value of the next byte.
  */
-byte cpu_get_next_byte(System *system);
+byte cpu_get_next_byte();
 
 /**
  * Gets the next word in the program.
@@ -57,7 +67,7 @@ byte cpu_get_next_byte(System *system);
  * @param system The system
  * @return The value of the next word.
  */
-word cpu_get_next_word(System *system);
+word cpu_get_next_word();
 
 /**
  * Pushes a byte in to the stack.
@@ -65,7 +75,7 @@ word cpu_get_next_word(System *system);
  * @param system The system 
  * @param value The value to push to the stack
  */
-void cpu_stack_push(System *system, byte value);
+void cpu_stack_push(byte value);
 
 /**
  * Pushes the execution context to the stack.
@@ -73,7 +83,7 @@ void cpu_stack_push(System *system, byte value);
  * 
  * @param system The system
  */
-void cpu_stack_push_context(System *system);
+void cpu_stack_push_context();
 
 /**
  * Pops a byte from the stack.
@@ -81,7 +91,7 @@ void cpu_stack_push_context(System *system);
  * @param system The system 
  * @return The value of the byte
  */
-byte cpu_stack_pop(System *system);
+byte cpu_stack_pop();
 
 /**
  * Pops an execution context from the stack and overwrite the current context.
@@ -89,13 +99,16 @@ byte cpu_stack_pop(System *system);
  * 
  * @param system The system 
  */
-void cpu_stack_pop_context(System *system);
+void cpu_stack_pop_context();
 
 /**
  * Adds wait cycles to the CPU.
  * 
  * @param cycle_count The number of cycle to wait 
  */
-void cpu_add_cycles(System *system, unsigned int cycle_count);
+void cpu_add_cycles(unsigned int cycle_count);
+
+void cpu_trigger_oam_dma();
+void cpu_trigger_nmi();
 
 #endif //CPU_CPU_H

cpu/decoding.c

@@ -7,52 +7,52 @@
 #include <assert.h>
 #include "log.h"
 
-address decode_operand_addr(System *system, AddressingMode addr_mode, bool *page_crossing) {
+address decode_operand_addr(AddressingMode addr_mode, bool *page_crossing) {
-    CPU registers = system->cpu;
+    CPU *registers = cpu_get_state();
     address operand_addr;
 
     if (addr_mode == ADDR_MODE_ZERO_PAGE) {
-        operand_addr = cpu_get_next_byte(system);
+        operand_addr = cpu_get_next_byte();
     } else if (addr_mode == ADDR_MODE_ZERO_PAGE_INDEXED_X) {
-        operand_addr = (cpu_get_next_byte(system) + registers.x) & 0xff;
+        operand_addr = (cpu_get_next_byte() + registers->x) & 0xff;
     } else if (addr_mode == ADDR_MODE_ZERO_PAGE_INDEXED_Y) {
-        operand_addr = (cpu_get_next_byte(system) + registers.y) & 0xff;
+        operand_addr = (cpu_get_next_byte() + registers->y) & 0xff;
     } else if (addr_mode == ADDR_MODE_ABSOLUTE) {
-        operand_addr = cpu_get_next_word(system);
+        operand_addr = cpu_get_next_word();
     } else if (addr_mode == ADDR_MODE_ABSOLUTE_INDEXED_X) {
-        word addr = cpu_get_next_word(system);
+        word addr = cpu_get_next_word();
-        word new_addr = addr + registers.x;
+        word new_addr = addr + registers->x;
 
         *page_crossing = (addr & 0xff00) != (new_addr & 0xff00);
 
         operand_addr = new_addr;
     } else if (addr_mode == ADDR_MODE_ABSOLUTE_INDEXED_Y) {
-        word addr = cpu_get_next_word(system);
+        word addr = cpu_get_next_word();
-        word new_addr = addr + registers.y;
+        word new_addr = addr + registers->y;
 
         *page_crossing = (addr & 0xff00) != (new_addr & 0xff00);
 
         operand_addr = new_addr;
     } else if (addr_mode == ADDR_MODE_INDIRECT_JUMP) {
-        word addr = cpu_get_next_word(system);
+        word addr = cpu_get_next_word();
         if ((addr & 0xff) == 0xff) {
             // Error in NES CPU for JMP op
-            word result = mem_get_byte(system, addr);
+            word result = mem_get_byte(addr);
-            result += mem_get_byte(system, addr & 0xff00) << 8;
+            result += mem_get_byte(addr & 0xff00) << 8;
             operand_addr = result;
         } else {
-            operand_addr = mem_get_word(system, addr);
+            operand_addr = mem_get_word(addr);
         }
     } else if (addr_mode == ADDR_MODE_INDIRECT_X) {
-        byte arg_addr = cpu_get_next_byte(system);
+        byte arg_addr = cpu_get_next_byte();
 
-        word addr = mem_get_byte(system, (arg_addr + system->cpu.x) & 0xff);
+        word addr = mem_get_byte((arg_addr + registers->x) & 0xff);
-        addr += mem_get_byte(system, (arg_addr + system->cpu.x + 1) & 0xff) << 8;
+        addr += mem_get_byte((arg_addr + registers->x + 1) & 0xff) << 8;
         operand_addr = addr;
     } else if (addr_mode == ADDR_MODE_INDIRECT_Y) {
-        byte arg_addr = cpu_get_next_byte(system);
+        byte arg_addr = cpu_get_next_byte();
-        word addr = mem_get_byte(system, arg_addr) + (mem_get_byte(system, (arg_addr + 1) & 0xff) << 8);
+        word addr = mem_get_byte(arg_addr) + (mem_get_byte((arg_addr + 1) & 0xff) << 8);
-        word new_addr = addr + registers.y;
+        word new_addr = addr + registers->y;
 
         *page_crossing = (addr & 0xff00) != (new_addr & 0xff00);
 
@@ -65,7 +65,7 @@ address decode_operand_addr(System *system, AddressingMode addr_mode, bool *page
     return operand_addr;
 }
 
-Operand decode_operand(System *system, AddressingMode addr_mode) {
+Operand decode_operand(AddressingMode addr_mode) {
     Operand operand;
 
     if (addr_mode == ADDR_MODE_ACCUMULATOR) {
@@ -74,25 +74,25 @@ Operand decode_operand(System *system, AddressingMode addr_mode) {
         operand.is_page_crossing = false;
     } else if (addr_mode == ADDR_MODE_IMMEDIATE) {
         operand.type = OPERAND_TYPE_IMMEDIATE;
-        operand.value = cpu_get_next_byte(system);
+        operand.value = cpu_get_next_byte();
         operand.is_page_crossing = false;
     } else {
         operand.type = OPERAND_TYPE_ADDRESS;
-        operand.value = decode_operand_addr(system, addr_mode, &operand.is_page_crossing);
+        operand.value = decode_operand_addr(addr_mode, &operand.is_page_crossing);
     }
 
     log_trace("Operand type: %s, value: %#02x", operand_name(&operand), operand.value);
     return operand;
 }
 
-byte read_operand(System *system, Operand operand) {
+byte read_operand(Operand operand) {
     switch (operand.type) {
         case OPERAND_TYPE_ACCUMULATOR:
-            return system->cpu.accumulator;
+            return cpu_get_state()->accumulator;
         case OPERAND_TYPE_IMMEDIATE:
             return (byte) operand.value;
         case OPERAND_TYPE_ADDRESS:
-            return mem_get_byte(system, operand.value);
+            return mem_get_byte(operand.value);
         default:
             assert(false);
     }

cpu/decoding.h

@@ -37,11 +37,11 @@ typedef struct {
     bool is_page_crossing;
 } Operand;
 
-address decode_operand_addr(System *system, AddressingMode addr_mode, bool *page_crossing);
+address decode_operand_addr(AddressingMode addr_mode, bool *page_crossing);
 
-Operand decode_operand(System *system, AddressingMode addr_mode);
+Operand decode_operand(AddressingMode addr_mode);
 
-byte read_operand(System *system, Operand operand);
+byte read_operand(Operand operand);
 
 char *get_addr_mode_name(AddressingMode addr_mode);
 

cpu/memory.c

@@ -6,6 +6,7 @@
 #include "log.h"
 #include "memory.h"
 #include "../include/rom.h"
+#include "cpu.h"
 
 #define RAM_MAX_ADDR 0x2000
 #define RAM_BANK_SIZE 0x800
@@ -14,36 +15,34 @@
 #define APU_MAX_ADDR 0x4020
 #define MAX_ADDR 0xffff
 
-byte mem_get_byte(System *system, address addr) {
+byte ram[RAM_SIZE];
+
+byte mem_get_byte(address addr) {
     assert(addr <= MAX_ADDR);
 
     if (addr >= RAM_MAX_ADDR && addr < PPU_MAX_ADDR) {
         byte reg = (addr - RAM_MAX_ADDR) % PPU_BANK_SIZE;
-        ppu_read_register(&system->ppu, reg);
+        ppu_read_register(reg);
-        return system->ppu.registers[reg];
     }
 
-    if (addr >= PPU_MAX_ADDR && addr < APU_MAX_ADDR) {
+    return ram[addr];
-        byte apu_addr = addr - PPU_MAX_ADDR;
-        return system->apu_registers[apu_addr];
-    }
-
-    return system->ram[addr];
 }
 
-word mem_get_word(System *system, address addr) {
+byte *mem_get_ptr(address addr) {
+    assert(addr <= MAX_ADDR);
+
+    return &ram[addr];
+}
+
+word mem_get_word(address addr) {
     assert(addr < MAX_ADDR);
 
-    if (addr >= RAM_MAX_ADDR && addr < APU_MAX_ADDR) {
+    word word = ram[addr];
-        assert(false);
+    word += ram[addr + 1] << 8;    // Little endian
-    }
-
-    word word = system->ram[addr];
-    word += system->ram[addr + 1] << 8;    // Little endian
     return word;
 }
 
-void mem_set_byte(System *system, address addr, byte byte) {
+void mem_set_byte(address addr, byte byte) {
     assert(addr < MAX_ADDR);
 
     log_trace("Writing '%02x' to address 0x%04x", byte, addr);
@@ -54,24 +53,24 @@ void mem_set_byte(System *system, address addr, byte byte) {
         // The value must also be cloned in the three mirrors
         for (int i = 0; i < 4; i++) {
             address ram_addr = init_ram_addr + RAM_BANK_SIZE * i;
-            system->ram[ram_addr] = byte;
+            ram[ram_addr] = byte;
         }
     } else if (addr < PPU_MAX_ADDR) {
         address reg_addr = (addr - RAM_MAX_ADDR) % PPU_BANK_SIZE;
 
         int bank_count = (PPU_MAX_ADDR - RAM_MAX_ADDR) / PPU_BANK_SIZE;
         for (int i = 0; i < bank_count; i++) {
-            address ram_addr = reg_addr + PPU_BANK_SIZE * i;
+            address ram_addr = reg_addr + PPU_BANK_SIZE * i + RAM_MAX_ADDR;
-            system->ppu.registers[ram_addr] = byte;
+            ram[ram_addr] = byte;
         }
 
-        ppu_write_register(&system->ppu, reg_addr);
+        ppu_write_register(reg_addr);
     } else {
-        system->ram[addr] = byte;
+        ram[addr] = byte;
 
         if (addr == PPU_REGISTER_OAM_DMA_ADDR) {
             // Writing to this address triggers an upload to the PPU memory
-            system->cpu.oam_dma_triggered = true;
+            cpu_trigger_oam_dma();
         }
     }
 }

cpu/memory.h

@@ -11,28 +11,34 @@
 /**
  * Gets a byte from a system's memory.
  *
- * @param system A reference to the system
  * @param addr The address to get
  * @return The value of the byte at the given address.
  */
-byte mem_get_byte(System *system, address addr);
+byte mem_get_byte(address addr);
+
+/**
+ * Gets a pointer to a byte in the memory.
+ * Should not be used by the CPU, because the PPU will not be triggered if reading some addresses.
+ *
+ * @param addr The address to get a pointer to
+ * @return A pointer to the byte in memory
+ */
+byte* mem_get_ptr(address addr);
 
 /**
  * Gets a word from a system's memory.
  *
- * @param system A reference to the system
  * @param addr The address to get
  * @return The value of the word at the given address.
  */
-word mem_get_word(System *system, address addr);
+word mem_get_word(address addr);
 
 /**
  * Sets a byte in a system's memory.
  *
- * @param system A reference to the system
  * @param addr The address to set
  * @param value The value to set
  */
-void mem_set_byte(System *system, address addr, byte value);
+void mem_set_byte(address addr, byte value);
 
 #endif //NESEMULATOR_MEMORY_H

cpu/op.h

@@ -17,7 +17,7 @@ enum op_code_base {
     OP_CODE_BASE_SBC = 0xe0
 };
 
-void process_op_code(System *system, byte op);
+void process_op_code(byte op);
 
 AddressingMode get_op_addr_mode(byte op_code);
 

debugger/cpu_view.c

@@ -7,24 +7,24 @@
 #include "../cpu/cpu.h"
 
 void cv_print(CpuView *view) {
-    window_print(view->window, 0, 0, "PC: $%04x", view->cpu->program_counter);
+    CPU *cpu_state = cpu_get_state();
-    window_print(view->window, 0, 1, "SP: %02x", view->cpu->stack_pointer);
+    window_print(view->window, 0, 0, "PC: $%04x", cpu_state->program_counter);
-    window_print(view->window, 0, 2, "A: %02x", view->cpu->accumulator);
+    window_print(view->window, 0, 1, "SP: %02x", cpu_state->stack_pointer);
-    window_print(view->window, 0, 3, "X: %02x", view->cpu->x);
+    window_print(view->window, 0, 2, "A: %02x", cpu_state->accumulator);
-    window_print(view->window, 0, 4, "Y: %02x", view->cpu->y);
+    window_print(view->window, 0, 3, "X: %02x", cpu_state->x);
-    window_print(view->window, 0, 5, "C: %01x", cpu_get_flag(view->cpu, CPU_STATUS_CARRY_MASK));
+    window_print(view->window, 0, 4, "Y: %02x", cpu_state->y);
-    window_print(view->window, 0, 6, "Z: %01x", cpu_get_flag(view->cpu, CPU_STATUS_ZERO_MASK));
+    window_print(view->window, 0, 5, "C: %01x", cpu_get_flag(CPU_STATUS_CARRY_MASK));
-    window_print(view->window, 0, 7, "I: %01x", cpu_get_flag(view->cpu, CPU_STATUS_INTERRUPT_DISABLE_MASK));
+    window_print(view->window, 0, 6, "Z: %01x", cpu_get_flag(CPU_STATUS_ZERO_MASK));
-    window_print(view->window, 0, 8, "D: %01x", cpu_get_flag(view->cpu, CPU_STATUS_DECIMAL_MASK));
+    window_print(view->window, 0, 7, "I: %01x", cpu_get_flag(CPU_STATUS_INTERRUPT_DISABLE_MASK));
-    window_print(view->window, 0, 9, "B: %01x", cpu_get_flag(view->cpu, CPU_STATUS_B_MASK));
+    window_print(view->window, 0, 8, "D: %01x", cpu_get_flag(CPU_STATUS_DECIMAL_MASK));
-    window_print(view->window, 0, 10, "O: %01x", cpu_get_flag(view->cpu, CPU_STATUS_OVERFLOW_MASK));
+    window_print(view->window, 0, 9, "B: %01x", cpu_get_flag(CPU_STATUS_B_MASK));
-    window_print(view->window, 0, 11, "N: %01x", cpu_get_flag(view->cpu, CPU_STATUS_NEGATIVE_MASK));
+    window_print(view->window, 0, 10, "O: %01x", cpu_get_flag(CPU_STATUS_OVERFLOW_MASK));
+    window_print(view->window, 0, 11, "N: %01x", cpu_get_flag(CPU_STATUS_NEGATIVE_MASK));
 }
 
-CpuView *cv_init(CPU *cpu, int x, int y) {
+CpuView *cv_init(int x, int y) {
     CpuView *view = malloc(sizeof(CpuView));
     view->window = malloc(sizeof(Window));
-    view->cpu = cpu;
 
     window_init(view->window, x, y, CPU_VIEW_WIDTH, CPU_VIEW_HEIGHT, "CPU VIEW");
     cv_print(view);

debugger/cpu_view.h

@@ -14,13 +14,12 @@
 
 typedef struct cpu_view {
     Window *window;
-    CPU *cpu;
 } CpuView;
 
 /**
  * Initializes a CPU view for a system RAM.
  */
-CpuView *cv_init(CPU *cpu, int x, int y);
+CpuView *cv_init(int x, int y);
 
 void cv_uninit(CpuView *cpu_view);
 

debugger/debugger.c

@@ -23,18 +23,18 @@ void debugger_create_window() {
     keypad(stdscr, true);
 }
 
-LinkedList debugger_create_interactive_windows(System *system) {
+LinkedList debugger_create_interactive_windows() {
     LinkedList interactive_windows;
     InteractWindow *window;
 
     interactive_windows = linked_list_init(true);
 
     window = malloc(sizeof(InteractWindow));
-    mv_init(window, system->ram, 0, 0);
+    mv_init(window, 0, 0);
     linked_list_add(&interactive_windows, window);
 
     window = malloc(sizeof(InteractWindow));
-    pv_init(window, system, MEMORY_VIEW_WIDTH, 0);
+    pv_init(window, MEMORY_VIEW_WIDTH, 0);
     linked_list_add(&interactive_windows, window);
 
     return interactive_windows;
@@ -62,8 +62,8 @@ void start_debugger(System *system) {
 
     interactive_windows = debugger_create_interactive_windows(system);
     current_window = interactive_windows.current->data;
-    cpu_view = cv_init(&system->cpu, 0, MEMORY_VIEW_HEIGHT);
+    cpu_view = cv_init(0, MEMORY_VIEW_HEIGHT);
-    ppu_view = ppv_init(&system->ppu, CPU_VIEW_WIDTH, MEMORY_VIEW_HEIGHT);
+    ppu_view = ppv_init(CPU_VIEW_WIDTH, MEMORY_VIEW_HEIGHT);
 
     cursor_enable(&current_window->cursor);
 

debugger/debugger.h

@@ -7,6 +7,6 @@
 
 #include "../include/system.h"
 
-void start_debugger(System *system);
+void start_debugger();
 
 #endif //NESEMULATOR_DEBUGGER_H

debugger/memory_view.c

@@ -3,6 +3,7 @@
 #include "memory_view.h"
 #include "dialog.h"
 #include "keys.h"
+#include "../cpu/memory.h"
 
 //
 // Created by william on 6/1/24.
@@ -40,10 +41,9 @@ void mv_handle_key_down(InteractWindow *window, int keycode) {
     }
 }
 
-void mv_init(InteractWindow *interact, ram ram, int x, int y) {
+void mv_init(InteractWindow *interact, int x, int y) {
     MemoryView *view = malloc(sizeof(MemoryView));
     view->window = interact;
-    view->ram = ram;
     view->base_address = 0x0000;
 
     interact->view = view;
@@ -61,7 +61,7 @@ void mv_init(InteractWindow *interact, ram ram, int x, int y) {
 void mv_print(MemoryView *view) {
     for (int line = 0; line <= MEMORY_VIEW_LINE_COUNT; line++) {
         address line_address = view->base_address + line * (MEMORY_VIEW_LINE_BYTE_COUNT + 1);
-        byte *data = &view->ram[line_address];
+        byte *data = mem_get_ptr(line_address);
 
         mv_write_line(view, line, line_address, data);
     }

debugger/memory_view.h

@@ -18,7 +18,6 @@
 
 typedef struct memory_view {
     InteractWindow *window;
-    byte *ram;
     address base_address;
 } MemoryView;
 
@@ -27,9 +26,8 @@ typedef struct memory_view {
  * The viewer base address will be set to 0x0000, and the cursor (0, 0).
  * The content of the memory will be printed on a new curses window.
  * @param view A pointer to the view to initialize
- * @param ram A pointer to the RAM
  */
-void mv_init(InteractWindow *interact, ram ram, int x, int y);
+void mv_init(InteractWindow *interact, int x, int y);
 
 /**
  * Prints the RAM content from the viewer base address.

debugger/ppu_view.c

@@ -6,7 +6,7 @@
 #include "ppu_view.h"
 
 void ppv_print_line(PpuView *view, byte reg, int line, char *fmt) {
-    int reg_value = view->ppu->registers[reg];
+    int reg_value = ppu_get_state()->registers[reg];
     window_print(view->window, 0, line, fmt);
 
     for (int i = 0; i < 0x8; i++) {
@@ -33,10 +33,9 @@ void ppv_print(PpuView *view) {
     ppv_print_line(view, PPU_REGISTER_DATA, 7, "    DATA:");
 }
 
-PpuView *ppv_init(PPU *ppu, int x, int y) {
+PpuView *ppv_init(int x, int y) {
     PpuView *view = malloc(sizeof(PpuView));
     view->window = malloc(sizeof(Window));
-    view->ppu = ppu;
 
     window_init(view->window, x, y, PPU_VIEW_WIDTH, PPU_VIEW_HEIGHT, "PPU VIEW");
     ppv_print(view);

debugger/ppu_view.h

@@ -13,10 +13,9 @@
 
 typedef struct ppu_view {
     Window *window;
-    PPU *ppu;
 } PpuView;
 
-PpuView *ppv_init(PPU *ppu, int x, int y);
+PpuView *ppv_init(int x, int y);
 
 void ppv_uninit(PpuView *ppu_view);
 

debugger/program_view.c

@@ -19,7 +19,7 @@ void decode_operands(ProgramView *view) {
             exit(EXIT_FAILURE);
         }
 
-        byte op_code = view->ram[pc];
+        byte op_code = mem_get_byte(pc);
         operand->addr = pc;
         operand->op_code = op_code;
         operand->addr_mode = get_op_addr_mode(op_code);
@@ -36,12 +36,12 @@ void decode_operands(ProgramView *view) {
             case ADDR_MODE_ZERO_PAGE:
             case ADDR_MODE_ZERO_PAGE_INDEXED_X:
             case ADDR_MODE_ZERO_PAGE_INDEXED_Y:
-                operand->value = view->ram[pc];
+                operand->value = mem_get_byte(pc);
                 pc += 1;
                 break;
             default:
-                operand->value = view->ram[pc];
+                operand->value = mem_get_byte(pc);
-                operand->value += view->ram[pc + 1] << 8;
+                operand->value += mem_get_byte(pc + 1) << 8;
                 pc += 2;
                 break;
         }
@@ -183,11 +183,10 @@ void pv_deinit(InteractWindow *window) {
     linked_list_uninit(&view->operands);
 }
 
-void pv_init(InteractWindow *interact, System *system, int x, int y) {
+void pv_init(InteractWindow *interact, int x, int y) {
     ProgramView *view = malloc(sizeof(ProgramView));
     view->window = interact;
-    view->ram = system->ram;
+    view->pc = &cpu_get_state()->program_counter;
-    view->pc = &system->cpu.program_counter;
     view->operands = linked_list_init(false);
 
     interact->view = view;

debugger/program_view.h

@@ -25,13 +25,12 @@ typedef struct debug_operand {
 
 typedef struct program_view {
     InteractWindow *window;
-    byte *ram;
     address *pc;
     LinkedList operands;
     LinkedListNode *first_operand_node;
     LinkedListNode *last_operand_node;
 } ProgramView;
 
-void pv_init(InteractWindow *interact, System *system, int x, int y);
+void pv_init(InteractWindow *interact, int x, int y);
 
 #endif //NESEMULATOR_PROGRAM_VIEW_H

include/cpu.h

@@ -1,7 +1,7 @@
 /*
  * =====================================================================================
  *
- *       Filename:  cpu.h
+ *       Filename:  cpu_state.h
  *
  *    Description:  6502 CPU emulator headers 
  *
@@ -22,8 +22,8 @@
 #ifndef NESEMULATOR_CPU_H
 #define NESEMULATOR_CPU_H
 
-void cpu_init(CPU *cpu);
+void cpu_init();
 
-void cpu_cycle(System *system);
+void cpu_cycle();
 
 #endif

include/mapper.h

@@ -10,7 +10,7 @@
 typedef struct mapper {
     address prg_rom_start_addr;
 
-    void (*post_prg_load)(ram, unsigned int);
+    void (*post_prg_load)(unsigned int);
 } Mapper;
 
 enum MapperType {

include/ppu.h

@@ -47,8 +47,8 @@
 #define PPU_MASK_NONE 0xff
 
 typedef struct ppu {
-    byte* registers;
+    byte *registers;
-    byte* oam_dma_register;
+    byte *oam_dma_register;
     byte vram[PPU_VRAM_SIZE];
     byte oam[PPU_OAM_SIZE];
     bool odd_frame;
@@ -56,15 +56,19 @@ typedef struct ppu {
     address t;
     byte x;
     bool w;
+
+    void (*trigger_nmi)();
 } PPU;
 
+PPU *ppu_get_state();
+
 /**
  * Initializes the PPU, according to the power up state.
  * https://www.nesdev.org/wiki/PPU_power_up_state
  *
  * @param ppu
  */
-void ppu_init(PPU *ppu, byte *registers_ram, byte *oam_dma_register);
+void ppu_init(byte *registers_ram, byte *oam_dma_register);
 
 /**
  * Cycles the PPU.
@@ -72,7 +76,7 @@ void ppu_init(PPU *ppu, byte *registers_ram, byte *oam_dma_register);
  * @param ppu
  * @param ram
  */
-void ppu_cycle(PPU *ppu);
+void ppu_cycle();
 
 /**
  * Read a flag from the PPU registers.
@@ -80,7 +84,7 @@ void ppu_cycle(PPU *ppu);
  * @param reg The register index
  * @param mask The flag mask
  */
-bool ppu_read_flag(PPU *ppu, size_t reg, byte mask);
+bool ppu_read_flag(size_t reg, byte mask);
 
 /**
  * Read a value from the PPU registers. Does not apply any offset to the value, a mask of 0x20 will either result in 0x20 (true) or 0x0 (false).
@@ -89,8 +93,8 @@ bool ppu_read_flag(PPU *ppu, size_t reg, byte mask);
  * @param reg The register index
  * @param mask The value mask
  */
-void ppu_read_register(PPU *ppu, byte reg);
+void ppu_read_register(byte reg);
 
-void ppu_write_register(PPU *ppu, byte reg);
+void ppu_write_register(byte reg);
 
 #endif //NESEMULATOR_PPU_H

include/rom.h

@@ -24,9 +24,8 @@ typedef struct {
  * Loads a ROM from a specified file path.
  *
  * @param path The file path
- * @param rom ROM
  * @return A boolean indicating a success (true) or an error.
  */
-bool rom_load(char *path, System *system);
+bool rom_load(char *path);
 
 #endif //NESEMULATOR_ROM_H

include/system.h

@@ -19,49 +19,33 @@
 #define PPU_REGISTER_OAM_DMA_ADDR 0x4014
 #define APU_REGISTERS_COUNT 24
 
-// Reference: https://www.nesdev.org/obelisk-6502-guide/registers.html
-typedef struct cpu {
-    address program_counter;
-    byte stack_pointer;
-    byte accumulator;
-    byte x;
-    byte y;
-    byte status;
-    bool oam_dma_triggered;
-    bool nmi_requested;
-} CPU;
-
 typedef struct system {
     void *rom_header;
-    CPU cpu;
-    PPU ppu;
     Mapper mapper;
-    ram ram;
     byte apu_registers[APU_REGISTERS_COUNT];
     unsigned long cycle_count;
 } System;
 
 /**
  * Initialize all components of a system.
- *
- * @param system The system to initialize
  */
-void system_init(System *system);
+void system_init();
 
-void system_start(System *system);
+void system_start();
 
 /**
  * Starts the main loop of a system.
- *
- * @param system The system
  */
-void system_loop(System *system);
+void system_loop();
 
 /**
  * De-initialize the components of a system.
- *
- * @param system The system to de-initialize
  */
-void system_uninit(System *system);
+void system_uninit();
+
+unsigned int system_get_cycles();
+void system_add_cycles(unsigned int cycles);
+
+Mapper *system_get_mapper();
 
 #endif //NESEMULATOR_SYSTEM_H

include/types.h

@@ -12,7 +12,7 @@ typedef unsigned char byte;
 typedef unsigned short address;
 typedef unsigned short word;
 
-typedef byte ram[RAM_SIZE];
+//typedef byte ram[RAM_SIZE];
 typedef byte vram[VRAM_SIZE];
 
 #endif //NESEMULATOR_TYPES_H

main.c

@@ -23,22 +23,20 @@
 #include "include/system.h"
 
 int main() {
-    System system;
-
     log_set_level(LOG_INFO);
-    system_init(&system);
+    system_init();
 
     char *rom_path = "../test_roms/smb.nes";
 
-    if (!rom_load(rom_path, &system)) {
+    if (!rom_load(rom_path)) {
-        system_uninit(&system);
+        system_uninit();
         return EXIT_FAILURE;
     }
 
-    system_start(&system);
+    system_start();
-//    start_debugger(&system);
+//    start_debugger();
-    system_loop(&system);
+    system_loop();
 
-    system_uninit(&system);
+    system_uninit();
     return EXIT_SUCCESS;
 }

mappers/simple_mapper.c

@@ -1,19 +1,20 @@
 #include "../include/mapper.h"
 #include "../include/rom.h"
+#include "../cpu/memory.h"
 #include <string.h>
 
 #define SIMPLE_MAPPER_PRG_START_ADDR 0x8000
 #define PRG_PART_SIZE 0x4000    // 16Kb
 
-void post_prg_load(ram ram, unsigned int prg_size) {
+void post_prg_load(unsigned int prg_size) {
     if (prg_size == 2) {
         // The whole space is occupied, nothing to do
         return;
     }
 
     // We need to mirror the data in the upper ram
-    byte *source = (byte *) &ram[SIMPLE_MAPPER_PRG_START_ADDR];
+    byte *source = mem_get_ptr(SIMPLE_MAPPER_PRG_START_ADDR);
-    byte *destination = (byte *) &ram[SIMPLE_MAPPER_PRG_START_ADDR + PRG_PART_SIZE];
+    byte *destination = mem_get_ptr(SIMPLE_MAPPER_PRG_START_ADDR + PRG_PART_SIZE);
     memcpy(destination, source, PRG_PART_SIZE);
 }
 

ppu/ppu.c

@@ -14,31 +14,56 @@
 // 10. This is where I'm stuck. I think I need to read the "sprites" section of https://wiki.nesdev.com/w/index.php/PPU_rendering very carefully.
 //
 
-#include <stddef.h>
 #include "../include/ppu.h"
 
-void ppu_init(PPU *ppu, byte *registers_ram, byte *oam_dma_register) {
+PPU ppu_state;
-    ppu->registers = registers_ram;
+
-    ppu->registers[PPU_REGISTER_CTRL] = 0x00;
+void ppu_init(byte *registers_ram, byte *oam_dma_register) {
-    ppu->registers[PPU_REGISTER_MASK] = 0x00;
+    ppu_state.registers = registers_ram;
-    ppu->registers[PPU_REGISTER_STATUS] = 0x00;
+    ppu_state.registers[PPU_REGISTER_CTRL] = 0x00;
-    ppu->registers[PPU_REGISTER_OAM_ADDR] = 0x00;
+    ppu_state.registers[PPU_REGISTER_MASK] = 0x00;
-    ppu->registers[PPU_REGISTER_OAM_DATA] = 0x00;
+    ppu_state.registers[PPU_REGISTER_STATUS] = 0x00;
-    ppu->registers[PPU_REGISTER_SCROLL] = 0x00;
+    ppu_state.registers[PPU_REGISTER_OAM_ADDR] = 0x00;
-    ppu->registers[PPU_REGISTER_ADDR] = 0x00;
+    ppu_state.registers[PPU_REGISTER_OAM_DATA] = 0x00;
-    ppu->registers[PPU_REGISTER_DATA] = 0x00;
+    ppu_state.registers[PPU_REGISTER_SCROLL] = 0x00;
-    ppu->oam_dma_register = oam_dma_register;
+    ppu_state.registers[PPU_REGISTER_ADDR] = 0x00;
-    ppu->odd_frame = false;
+    ppu_state.registers[PPU_REGISTER_DATA] = 0x00;
+    ppu_state.oam_dma_register = oam_dma_register;
+    ppu_state.odd_frame = false;
+}
+
+PPU *ppu_get_state() {
+    return &ppu_state;
+}
+
+void ppu_status_set(byte mask, bool enabled) {
+    if (enabled) {
+        ppu_state.registers[PPU_REGISTER_STATUS] |= mask;
+    } else {
+        ppu_state.registers[PPU_REGISTER_STATUS] &= ~mask;
+    }
 }
 
 long frame = 0;
 int x, y = 0;
 
-void ppu_cycle(PPU *ppu) {
+void ppu_cycle() {
+    if (x == 1) {
+        if (y == 241) {
+            // VBlank start
+            ppu_status_set(PPU_STATUS_VBLANK, true);
+        }
+
+        if (y == 261) {
+            // VBlank clear
+            ppu_status_set(PPU_STATUS_VBLANK, false);
+        }
+    }
+
     int frame_width = 341;
     int frame_height = 262;
-    bool rendering_enabled = ppu_read_flag(ppu, PPU_REGISTER_MASK, PPU_MASK_SHOW_BG | PPU_MASK_SHOW_SP);
+    bool rendering_enabled = ppu_read_flag(PPU_REGISTER_MASK, PPU_MASK_SHOW_BG | PPU_MASK_SHOW_SP);
-    if (rendering_enabled && ppu->odd_frame) {
+    if (rendering_enabled && ppu_state.odd_frame) {
         // With rendering enabled, the odd frames are shorter
         // TODO: and doing the last cycle of the last dummy nametable fetch there instead
         frame_width = 339;
@@ -54,30 +79,30 @@ void ppu_cycle(PPU *ppu) {
     if (y >= frame_height) {
         y = 0;
         frame++;
-        ppu->odd_frame = !ppu->odd_frame;
+        ppu_state.odd_frame = !ppu_state.odd_frame;
     }
 }
 
-bool ppu_read_flag(PPU *ppu, size_t reg, byte mask) {
+bool ppu_read_flag(size_t reg, byte mask) {
-    return ppu->registers[reg] & mask;
+    return ppu_state.registers[reg] & mask;
 }
 
-//byte ppu_read_register(PPU *ppu, size_t reg, byte mask) {
+//byte ppu_read_register(size_t reg, byte mask) {
-//    return ppu->registers[reg] & mask;
+//    return ppu_state.registers[reg] & mask;
 //}
 
-void ppu_read_register(PPU *ppu, byte reg) {
+void ppu_read_register(byte reg) {
     if (reg == PPU_REGISTER_STATUS) {
-        ppu->w = false;
+        ppu_state.w = false;
     }
 }
 
-void ppu_write_register(PPU *ppu, byte reg) {
+void ppu_write_register(byte reg) {
     if (reg == PPU_REGISTER_SCROLL || reg == PPU_REGISTER_ADDR) {
-        ppu->w = !ppu->w;
+        ppu_state.w = !ppu_state.w;
     }
 
     if (reg == PPU_REGISTER_OAM_DATA) {
-        ppu->registers[PPU_REGISTER_OAM_ADDR]++;
+        ppu_state.registers[PPU_REGISTER_OAM_ADDR]++;
     }
 }

rom/ines.c

@@ -7,6 +7,7 @@
 #include "log.h"
 #include "../include/rom.h"
 #include "../include/system.h"
+#include "../cpu/memory.h"
 
 // Flag 6
 #define NES_HEADER_FLAG_MIRRORING 0x01
@@ -126,21 +127,22 @@ bool rom_ines_read_trainer(FILE *file, INesHeader *header) {
     return false;
 }
 
-bool rom_ines_read_prg_rom(FILE *file, INesHeader *header, System *system) {
+bool rom_ines_read_prg_rom(FILE *file, INesHeader *header) {
     unsigned int prg_rom_size = header->prg_rom_size * 16384;
     log_debug("Reading %d bytes PRG ROM", prg_rom_size);
 
-    if (fread(&system->ram[system->mapper.prg_rom_start_addr], sizeof(byte), prg_rom_size, file) < prg_rom_size) {
+    byte *prg_rom_location = mem_get_ptr(system_get_mapper()->prg_rom_start_addr);
+    if (fread(prg_rom_location, sizeof(byte), prg_rom_size, file) < prg_rom_size) {
         log_error("Failed to read PRG ROM");
         return false;
     }
 
-    system->mapper.post_prg_load(&system->ram[0], header->prg_rom_size);
+    system_get_mapper()->post_prg_load(header->prg_rom_size);
 
     return true;
 }
 
-bool rom_ines_read_chr_rom(FILE *file, INesHeader *header, System *system) {
+bool rom_ines_read_chr_rom(FILE *file, INesHeader *header) {
     if (header->chr_rom_size <= 0) {
         log_debug("No CHR ROM to read");
         return true;
@@ -149,7 +151,8 @@ bool rom_ines_read_chr_rom(FILE *file, INesHeader *header, System *system) {
     unsigned int chr_rom_size = header->chr_rom_size * 8192;
     log_debug("Reading %d bytes CHR ROM", chr_rom_size);
 
-    if (fread(system->ppu.vram, sizeof(byte), chr_rom_size, file) < chr_rom_size) {
+    byte *chr_rom_location = ppu_get_state()->vram;
+    if (fread(chr_rom_location, sizeof(byte), chr_rom_size, file) < chr_rom_size) {
         log_error("Failed to read CHR ROM");
         return false;
     }
@@ -157,11 +160,11 @@ bool rom_ines_read_chr_rom(FILE *file, INesHeader *header, System *system) {
     return true;
 }
 
-bool rom_ines_read(const char header_buf[ROM_HEADER_SIZE], FILE *file, System *system) {
+bool rom_ines_read(const char header_buf[ROM_HEADER_SIZE], FILE *file) {
     INesHeader header = read_header(header_buf);
-    system->rom_header = &header;
+//    system->rom_header = &header;
 
     return rom_ines_read_trainer(file, &header) &&
-           rom_ines_read_prg_rom(file, &header, system) &&
+           rom_ines_read_prg_rom(file, &header) &&
-           rom_ines_read_chr_rom(file, &header, system);
+           rom_ines_read_chr_rom(file, &header);
 }

rom/rom.c

@@ -8,7 +8,7 @@
 #include "ines.c"
 #include "../include/system.h"
 
-bool rom_load(char *path, System *system) {
+bool rom_load(char *path) {
     FILE *file = fopen(path, "r");
     if (!file) {
         log_error("Failed to open ROM");
@@ -28,7 +28,7 @@ bool rom_load(char *path, System *system) {
     }
 
     log_info("Reading iNes 1.0 ROM at %s", path);
-    rom_ines_read(header_buffer, file, system);
+    rom_ines_read(header_buffer, file);
 
     if (fclose(file) != 0) {
         log_error("Failed to close ROM file");

system.c

@@ -7,25 +7,27 @@
 #include "memory.h"
 #include <unistd.h>
 #include <assert.h>
-#include "log.h"
+#include "cpu.h"
 
-void system_init(System *system) {
+System current_sys;
-    byte *registers_base_addr = &system->ram[PPU_REGISTERS_BASE_ADDR];
-    byte *oam_dma_register = &system->ram[PPU_REGISTER_OAM_DMA_ADDR];
 
-    cpu_init(&system->cpu);
+void system_init() {
-    ppu_init(&system->ppu, registers_base_addr, oam_dma_register);
+    byte *registers_base_addr = mem_get_ptr(PPU_REGISTERS_BASE_ADDR);
+    byte *oam_dma_register = mem_get_ptr(PPU_REGISTER_OAM_DMA_ADDR);
 
-    system->mapper = get_mapper(MAPPER_TYPE_SIMPLE);
+    cpu_init();
-    system->cycle_count = 7;
+    ppu_init(registers_base_addr, oam_dma_register);
+
+    current_sys.mapper = get_mapper(MAPPER_TYPE_SIMPLE);
+    current_sys.cycle_count = 7;
 }
 
-void system_start(System *system) {
+void system_start() {
-    address pc = mem_get_word(system, 0xfffc);
+    address pc = mem_get_word(0xfffc);
-    system->cpu.program_counter = pc;
+    cpu_get_state()->program_counter = pc;
 }
 
-void system_loop(System *system) {
+void system_loop() {
     assert(CPU_CLOCK_DIVISOR > PPU_CLOCK_DIVISOR);
 
     unsigned int master_cycle_per_frame = MASTER_CLOCK / FRAME_RATE;
@@ -37,14 +39,14 @@ void system_loop(System *system) {
     while (true) {
 //        log_info("Frame %d", frame);
 
-        while (system->cycle_count < cpu_cycle_per_frame * frame) {
+        while (current_sys.cycle_count < cpu_cycle_per_frame * frame) {
-            if (cpu_cycle_count == system->cycle_count) {
+            if (cpu_cycle_count == current_sys.cycle_count) {
-                cpu_cycle(system);
+                cpu_cycle();
             }
             cpu_cycle_count++;
 
             for (int ppu_c = 0; ppu_c < ppu_cycle_per_cpu_cycle; ppu_c++) {
-                ppu_cycle(&system->ppu);
+                ppu_cycle();
             }
         }
 
@@ -53,5 +55,17 @@ void system_loop(System *system) {
     }
 }
 
-void system_uninit(System *system) {
+void system_uninit() {
+}
+
+unsigned int system_get_cycles() {
+    return current_sys.cycle_count;
+}
+
+void system_add_cycles(unsigned int cycles) {
+    current_sys.cycle_count += cycles;
+}
+
+Mapper *system_get_mapper() {
+    return &current_sys.mapper;
 }