152 lines
4.0 KiB
C
152 lines
4.0 KiB
C
#include <log.h>
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#include <assert.h>
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#include <string.h>
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#include "../include/cpu.h"
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#include "cpu.h"
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#include "memory.h"
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#include "op.h"
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/*
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* =====================================================================================
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*
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* Filename: cpu.c
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*
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* Description: 6502 CPU emulator
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*
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* Version: 1.0
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* Created: 2023-09-21 10:10:26 PM
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* Revision: none
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* Compiler: gcc
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*
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* Author: William Nolin,
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* Organization:
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*
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* =====================================================================================
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*/
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void cpu_init(CPU *cpu) {
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cpu->program_counter = 0x8000;
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cpu->stack_pointer = 0xfd;
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cpu->accumulator = 0x00;
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cpu->x = 0x00;
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cpu->y = 0x00;
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cpu->status = 0x04;
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cpu->oam_dma_triggered = false;
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}
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void print_registers(CPU cpu, byte op, unsigned long cycle_count) {
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log_debug("%#02x %#02x %s \t A:%#02x X:%#02x Y:%#02x F:%#02x SP:%#02x \t [%d]",
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cpu.program_counter,
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op,
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get_op_code_name(op),
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cpu.accumulator,
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cpu.x,
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cpu.y,
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cpu.status,
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cpu.stack_pointer,
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cycle_count);
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}
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void oam_dma_upload(System *system) {
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byte page_high_addr = *system->ppu.oam_dma_register;
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address page_addr = ((address) page_high_addr) << 8;
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byte n = 0xff;
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byte *ram_source = &system->ram[page_addr];
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byte *oam_destination = system->ppu.oam;
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memcpy(oam_destination, ram_source, n);
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log_debug("OAM DMA %#04x", page_addr);
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cpu_add_cycles(system, 513); // TODO
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}
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void cpu_cycle(System *system) {
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if (system->cpu.oam_dma_triggered) {
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oam_dma_upload(system);
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system->cpu.oam_dma_triggered = false;
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return;
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}
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CPU registers = system->cpu;
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byte op = cpu_get_next_byte(system);
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print_registers(registers, op, system->cycle_count);
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process_op_code(system, op);
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}
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void cpu_add_cycles(System *system, unsigned int cycle_count) {
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system->cycle_count += cycle_count;
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}
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// === Registers ===
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bool cpu_get_flag(System *system, byte mask) {
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return system->cpu.status & mask;
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}
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void cpu_set_flag(System *system, byte mask, bool set) {
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if (set) {
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system->cpu.status |= mask;
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} else {
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system->cpu.status &= ~mask;
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}
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}
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byte cpu_get_next_byte(System *system) {
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byte next_byte = mem_get_byte(system, system->cpu.program_counter);
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system->cpu.program_counter++;
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return next_byte;
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}
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word cpu_get_next_word(System *system) {
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word next_word = mem_get_word(system, system->cpu.program_counter);
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system->cpu.program_counter += 2;
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return next_word;
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}
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void cpu_stack_push(System *system, byte value) {
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assert(system->cpu.stack_pointer > 0);
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address mem_addr = CPU_STACK_ADDR | system->cpu.stack_pointer;
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mem_set_byte(system, mem_addr, value);
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system->cpu.stack_pointer--;
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}
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byte cpu_stack_pop(System *system) {
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assert(system->cpu.stack_pointer < 0xff);
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system->cpu.stack_pointer++;
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address mem_addr = CPU_STACK_ADDR | system->cpu.stack_pointer;
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byte value = mem_get_byte(system, mem_addr);
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return value;
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}
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void cpu_stack_push_context(System *system) {
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cpu_stack_push(system, system->cpu.program_counter >> 8);
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cpu_stack_push(system, system->cpu.program_counter & 0xff);
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cpu_stack_push(system, system->cpu.status);
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}
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void cpu_stack_pop_context(System *system) {
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byte value = cpu_stack_pop(system);
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value &= 0xef; // The B mask cannot be set as it is a CPU signal
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value |= 0x20; // This value is always set
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system->cpu.status = value;
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byte lo = cpu_stack_pop(system);
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address pc = cpu_stack_pop(system) << 8;
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pc += lo;
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system->cpu.program_counter = pc;
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}
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char *operand_name(Operand *operand) {
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switch (operand->type) {
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case OPERAND_TYPE_ACCUMULATOR:
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return "Accumulator";
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case OPERAND_TYPE_IMMEDIATE:
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return "Immediate";
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case OPERAND_TYPE_ADDRESS:
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return "Address";
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}
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} |