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// NOTE(peter): You can enable decimal mode by adding this to the compilerflags -dENABLE_DECIMAL_MODE DO NOT ENABLE FOR NES!!!
#define PAGE_CROSSED(base, addr) (((base ^ addr) > 0xff))
static inline uint8_t pack_flags(struct cpu_state *cpu) {
return (cpu->n << 7) | (cpu->v << 6) | (1 << 5) | (cpu->d << 3) | (cpu->i << 2) | (cpu->z << 1) | cpu->c;
}
__attribute__((always_inline))
static inline void unpack_flags(struct cpu_state *cpu, uint8_t value) {
cpu->n = (value >> 7) & 1;
cpu->v = (value >> 6) & 1;
cpu->d = (value >> 3) & 1;
cpu->i = (value >> 2) & 1;
cpu->z = (value >> 1) & 1;
cpu->c = value & 1;
}
__attribute__((always_inline))
static inline void update_zn(struct cpu_state *cpu, uint8_t result) {
cpu->z = (result == 0);
cpu->n = (result & 0x80) != 0;
}
static void (*opcode_lut[256])(struct nes_state *) __attribute__((aligned(4096)));
#include "mknes_cpu_opcodes.c"
#include "mknes_cpu_opcodes_ud.c"
static inline void do_nmi(struct nes_state *state) {
struct cpu_state * restrict cpu = &state->cpu;
memory_read_dummy(state, cpu->pc); // T1: dummy read (fetch suppressed)
uint8_t pcl = cpu->pc & 0xff;
uint8_t pch = cpu->pc >> 8;
memory_write(state, 0x0100 + cpu->sp--, pch); // T2
memory_write(state, 0x0100 + cpu->sp--, pcl); // T3
memory_write(state, 0x0100 + cpu->sp--, pack_flags(cpu) & ~0x10); // T4: push P (B flag clear)
uint8_t lo = memory_read(state, 0xfffa); // T5
uint8_t hi = memory_read(state, 0xfffb); // T6
cpu->pc = lo | (hi << 8); // T7
cpu->i = 1;
}
static inline void do_irq(struct nes_state *state) {
struct cpu_state * restrict cpu = &state->cpu;
memory_read_dummy(state, cpu->pc); // T1: dummy read (fetch suppressed)
uint8_t pcl = cpu->pc & 0xff;
uint8_t pch = cpu->pc >> 8;
memory_write(state, 0x0100 + cpu->sp--, pch); // T2
memory_write(state, 0x0100 + cpu->sp--, pcl); // T3
memory_write(state, 0x0100 + cpu->sp--, pack_flags(cpu) & ~0x10); // T4: push P (B flag clear)
uint8_t lo = memory_read(state, 0xfffe); // T5
uint8_t hi = memory_read(state, 0xffff); // T6
cpu->pc = lo | (hi << 8); // T7
cpu->i = 1;
}
__attribute__((always_inline))
static inline void check_interrupts(struct nes_state *state) {
struct cpu_state * restrict cpu = &state->cpu;
if(state->cpu.nmi_pending) {
state->cpu.nmi_pending = 0;
do_nmi(state);
} else if(state->cpu.irq_pending && cpu->i == 0) {
state->cpu.irq_pending = 0;
do_irq(state);
}
}
static inline void cpu_reset(struct nes_state *state) {
uint32_t lo = state->mapper_function.prg_rom_read(state, 0xfffc);
uint32_t hi = state->mapper_function.prg_rom_read(state, 0xfffd);
state->cpu.sp = 0xfd;
state->cpu.i = 1;
state->cpu.pc = (hi << 8) | lo;
}
static inline void cpu_tick(struct nes_state *state) {
struct cpu_state * restrict cpu = &state->cpu;
// check_interrupts(state);
if(state->cpu.nmi_pending) {
state->cpu.nmi_pending = 0;
do_nmi(state);
}
if(state->cpu.irq_pending && cpu->i == 0) {
state->cpu.irq_pending = 0;
do_irq(state);
}
// printf("%4.4x: ", cpu->pc);
uint8_t opcode = memory_read(state, cpu->pc++);
// printf("%2.2x a:%2.2x x:%2.2x y:%2.2x p:%2.2x sp:%2.2x cycle: %ld\n", opcode, cpu->a, cpu->x, cpu->y, pack_flags(cpu), cpu->sp, state->cycles);
opcode_lut[opcode](state);
}
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