142 lines
3.7 KiB
C
142 lines
3.7 KiB
C
#include <log.h>
|
|
#include <assert.h>
|
|
#include <string.h>
|
|
#include "../include/cpu.h"
|
|
#include "cpu.h"
|
|
#include "memory.h"
|
|
#include "op.h"
|
|
#include "decoding.h"
|
|
|
|
/*
|
|
* =====================================================================================
|
|
*
|
|
* Filename: cpu.c
|
|
*
|
|
* Description: 6502 CPU emulator
|
|
*
|
|
* Version: 1.0
|
|
* Created: 2023-09-21 10:10:26 PM
|
|
* Revision: none
|
|
* Compiler: gcc
|
|
*
|
|
* Author: William Nolin,
|
|
* Organization:
|
|
*
|
|
* =====================================================================================
|
|
*/
|
|
|
|
void cpu_init(CPU *cpu) {
|
|
cpu->program_counter = 0x8000;
|
|
cpu->stack_pointer = 0xfd;
|
|
cpu->accumulator = 0x00;
|
|
cpu->x = 0x00;
|
|
cpu->y = 0x00;
|
|
cpu->status = 0x04;
|
|
cpu->oam_dma_triggered = false;
|
|
}
|
|
|
|
void print_registers(CPU cpu, byte op, unsigned long cycle_count) {
|
|
log_debug("%#02x %#02x %s \t A:%#02x X:%#02x Y:%#02x F:%#02x SP:%#02x \t [%d]",
|
|
cpu.program_counter,
|
|
op,
|
|
get_op_code_name(op),
|
|
cpu.accumulator,
|
|
cpu.x,
|
|
cpu.y,
|
|
cpu.status,
|
|
cpu.stack_pointer,
|
|
cycle_count);
|
|
}
|
|
|
|
void oam_dma_upload(System *system) {
|
|
byte page_high_addr = *system->ppu.oam_dma_register;
|
|
address page_addr = ((address) page_high_addr) << 8;
|
|
byte n = 0xff;
|
|
|
|
byte *ram_source = &system->ram[page_addr];
|
|
byte *oam_destination = system->ppu.oam;
|
|
|
|
memcpy(oam_destination, ram_source, n);
|
|
|
|
log_debug("OAM DMA %#04x", page_addr);
|
|
cpu_add_cycles(system, 513); // TODO
|
|
}
|
|
|
|
void cpu_cycle(System *system) {
|
|
if (system->cpu.oam_dma_triggered) {
|
|
oam_dma_upload(system);
|
|
system->cpu.oam_dma_triggered = false;
|
|
return;
|
|
}
|
|
|
|
CPU registers = system->cpu;
|
|
byte op = cpu_get_next_byte(system);
|
|
|
|
print_registers(registers, op, system->cycle_count);
|
|
|
|
process_op_code(system, op);
|
|
}
|
|
|
|
void cpu_add_cycles(System *system, unsigned int cycle_count) {
|
|
system->cycle_count += cycle_count;
|
|
}
|
|
|
|
// === Registers ===
|
|
bool cpu_get_flag(System *system, byte mask) {
|
|
return system->cpu.status & mask;
|
|
}
|
|
|
|
void cpu_set_flag(System *system, byte mask, bool set) {
|
|
if (set) {
|
|
system->cpu.status |= mask;
|
|
} else {
|
|
system->cpu.status &= ~mask;
|
|
}
|
|
}
|
|
|
|
byte cpu_get_next_byte(System *system) {
|
|
byte next_byte = mem_get_byte(system, system->cpu.program_counter);
|
|
system->cpu.program_counter++;
|
|
return next_byte;
|
|
}
|
|
|
|
word cpu_get_next_word(System *system) {
|
|
word next_word = mem_get_word(system, system->cpu.program_counter);
|
|
system->cpu.program_counter += 2;
|
|
return next_word;
|
|
}
|
|
|
|
void cpu_stack_push(System *system, byte value) {
|
|
assert(system->cpu.stack_pointer > 0);
|
|
|
|
address mem_addr = CPU_STACK_ADDR | system->cpu.stack_pointer;
|
|
mem_set_byte(system, mem_addr, value);
|
|
system->cpu.stack_pointer--;
|
|
}
|
|
|
|
byte cpu_stack_pop(System *system) {
|
|
assert(system->cpu.stack_pointer < 0xff);
|
|
|
|
system->cpu.stack_pointer++;
|
|
address mem_addr = CPU_STACK_ADDR | system->cpu.stack_pointer;
|
|
byte value = mem_get_byte(system, mem_addr);
|
|
return value;
|
|
}
|
|
|
|
void cpu_stack_push_context(System *system) {
|
|
cpu_stack_push(system, system->cpu.program_counter >> 8);
|
|
cpu_stack_push(system, system->cpu.program_counter & 0xff);
|
|
cpu_stack_push(system, system->cpu.status);
|
|
}
|
|
|
|
void cpu_stack_pop_context(System *system) {
|
|
byte value = cpu_stack_pop(system);
|
|
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;
|
|
|
|
byte lo = cpu_stack_pop(system);
|
|
address pc = cpu_stack_pop(system) << 8;
|
|
pc += lo;
|
|
system->cpu.program_counter = pc;
|
|
} |