add preliminary apu register support
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c0679b404d
commit
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2
Makefile
2
Makefile
@ -1,7 +1,7 @@
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CFLAGS = -O2 -Wall -Wextra -pedantic -Wno-unused-parameter
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nes:
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${CC} ${CFLAGS} -o nes cpu.c rom.c ppu.c
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${CC} ${CFLAGS} -o nes cpu.c rom.c ppu.c apu.c
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test: nes
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./nes ${HOME}/src/other/nes-test-roms/other/nestest.nes
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55
apu.c
Normal file
55
apu.c
Normal file
@ -0,0 +1,55 @@
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#include <stdio.h>
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#include <string.h>
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#include "apu.h"
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struct apu apu = {0};
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void
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apu_init(void)
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{
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memset(&apu, 0, sizeof(apu));
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}
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uint8_t
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apu_read(uint16_t addr)
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{
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switch (addr) {
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/* pulse1 */
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case 0x4000:
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return (apu.pulse1.duty << 6) | (apu.pulse1.envelope << 5)
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| (apu.pulse1.const_vol << 4) | apu.pulse1.envelope_vol;
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case 0x4001:
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return (apu.pulse1.sweep_enable << 7) | (apu.pulse1.sweep_period << 4)
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| (apu.pulse1.sweep_negative << 3) | apu.pulse1.sweep_shift_count;
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case 0x4002:
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return apu.pulse1.timer_low;
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case 0x4003:
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return (apu.pulse1.length_counter_load << 3) | apu.pulse1.timer_high;
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/* pulse2 */
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case 0x4004:
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return (apu.pulse2.duty << 6) | (apu.pulse2.envelope << 5)
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| (apu.pulse2.const_vol << 4) | apu.pulse2.envelope_vol;
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case 0x4005:
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return (apu.pulse1.sweep_enable << 7) | (apu.pulse1.sweep_period << 4)
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| (apu.pulse1.sweep_negative << 3) | apu.pulse1.sweep_shift_count;
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case 0x4006:
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return apu.pulse1.timer_low;
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case 0x4007:
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return (apu.pulse1.length_counter_load << 3) | apu.pulse1.timer_high;
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/* status */
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case 0x4015:
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return (apu.status.dmc_int << 7) | (apu.status.frame_int << 6)
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| (apu.status.dmc_active << 4) | (apu.status.lc_noise << 3)
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| (apu.status.lc_triangle << 2) | (apu.status.lc_pulse2 << 1)
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| apu.status.lc_pulse1;
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default:
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fprintf(stderr, "Invalid APU read at $%04X!\n", addr);
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return 0;
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};
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}
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void
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apu_write(uint16_t addr, uint8_t byte)
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{
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}
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105
apu.h
Normal file
105
apu.h
Normal file
@ -0,0 +1,105 @@
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#ifndef APU_H
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#define APU_H
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#include <stdint.h>
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struct pulse {
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/* $4000/$4004 */
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uint8_t duty : 2;
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uint8_t envelope : 1;
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uint8_t const_vol : 1;
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uint8_t envelope_vol : 4;
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/* $4001/$4005 */
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uint8_t sweep_enable : 1;
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uint8_t sweep_period : 3;
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uint8_t sweep_negative : 1;
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uint8_t sweep_shift_count : 3;
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/* $4002/$4006 */
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uint8_t timer_low;
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/* $4003/$4007 */
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uint8_t length_counter_load : 5;
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uint8_t timer_high : 3;
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};
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struct triangle {
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/* $4008 */
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uint8_t counter_disable : 1;
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uint8_t counter_reload : 7;
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/* $400A */
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uint8_t timer_low;
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/* $400B */
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uint8_t counter_load : 5;
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uint8_t timer_high : 3;
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};
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struct noise {
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/* $400C */
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uint8_t padding1 : 2;
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uint8_t loop_envelope : 1;
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uint8_t constant_volume : 1;
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uint8_t envelope_volume : 4;
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/* $400E */
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uint8_t loop_noise : 1;
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uint8_t padding2 : 3;
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uint8_t noise_period : 4;
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/* $400F */
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uint8_t length_counter_load : 5;
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uint8_t padding3 : 3;
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};
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struct dmc {
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/* $4010 */
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uint8_t irq_enable : 1;
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uint8_t loop : 1;
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uint8_t padding1 : 2;
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uint8_t frequency : 4;
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/* $4011 */
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uint8_t padding2 : 1;
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uint8_t load_counter : 7;
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/* $4012 */
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uint8_t sample_addr;
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/* $4013 */
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uint8_t sample_length;
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};
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struct apu {
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/* $4000-$4013 (write) */
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struct pulse pulse1;
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struct pulse pulse2;
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struct triangle triangle;
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struct noise noise;
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struct dmc dmc;
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/* $4015 (write) */
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struct control {
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uint8_t padding : 3;
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uint8_t dmc_enable : 1;
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uint8_t noise_enable : 1;
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uint8_t triangle_enable : 1;
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uint8_t pulse2_enable : 1;
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uint8_t pulse1_enable : 1;
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} control;
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/* $4015 (read) */
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struct status {
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uint8_t dmc_int : 1;
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uint8_t frame_int : 1;
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uint8_t padding : 1;
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uint8_t dmc_active : 1;
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uint8_t lc_noise : 1;
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uint8_t lc_triangle : 1;
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uint8_t lc_pulse2 : 1;
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uint8_t lc_pulse1 : 1;
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} status;
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/* $4017 (write) */
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struct frame_counter {
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uint8_t mode : 1;
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uint8_t irq_inhibit : 1;
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uint8_t padding : 6;
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} frame_counter;
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};
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extern struct apu apu;
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void apu_tick(void);
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uint8_t apu_read(uint16_t addr);
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void apu_write(uint16_t addr, uint8_t byte);
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#endif /* APU_H */
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13
cpu.c
13
cpu.c
@ -5,10 +5,11 @@
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#include <stdlib.h>
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#include <string.h>
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#include "apu.h"
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#include "cpu.h"
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#include "opcodes.h"
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#include "rom.h"
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#include "ppu.h"
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#include "rom.h"
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#define MAX(a, b) ((a > b) ? a : b)
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@ -53,9 +54,10 @@ peek(uint16_t addr)
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return rom.prg_rom[addr - 0x8000];
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else
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fprintf(stderr, "PRG ROG size is not 0x4000 nor 0x8000\n"), exit(1);
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} else {
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} else if ((addr >= 0x4000 && addr <= 0x4013) || addr == 0x4015 || addr == 0x4017)
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return apu_read(addr);
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else
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return memory[addr];
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}
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}
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static uint16_t
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@ -68,6 +70,11 @@ peek16(uint16_t addr)
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static void
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memwrite(uint16_t addr, uint8_t byte)
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{
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if (addr >= 0x4000 && addr <= 0x4017) {
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apu_write(addr, byte);
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return;
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}
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MEMORY_MIRROR(addr);
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memory[addr] = byte;
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