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gb6
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fix push and pop, add more extended instructions

This commit is contained in:
Matt Laux 2019-04-25 00:19:47 -05:00
parent ed785440fc
commit b6966cb605
6 changed files with 106 additions and 17 deletions
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81
src/cpu.c
View File

@ -137,24 +137,41 @@ static void dec_with_carry(struct cpu *regs, u8 *reg)
set_flag(regs, FLAG_ZERO);
}
static void rotate_left(struct cpu *regs, u8 *reg)
static u8 rotate_left(struct cpu *regs, u8 reg)
{
// copy old leftmost bit to carry flag
regs->f = (*reg & 0x80) >> 3 | (regs->f & ~FLAG_CARRY);
regs->f = (reg & 0x80) >> 3 | (regs->f & ~FLAG_CARRY);
// rotate
*reg <<= 1;
int result = reg << 1;
// restore leftmost (now rightmost) bit
*reg |= (regs->f & FLAG_CARRY) >> 4;
result |= (regs->f & FLAG_CARRY) >> 4;
return result;
}
static void rotate_right(struct cpu *regs, u8 *reg)
static u8 rotate_right(struct cpu *regs, u8 reg)
{
// copy old rightmost bit to carry flag
regs->f = (*reg & 0x01) << 4 | (regs->f & ~FLAG_CARRY);
regs->f = (reg & 0x01) << 4 | (regs->f & ~FLAG_CARRY);
// rotate
*reg >>= 1;
int result = reg >> 1;
// restore rightmost bit to left
*reg |= (regs->f & FLAG_CARRY) << 3;
result |= (regs->f & FLAG_CARRY) << 3;
return result;
}
static u8 shift_left(struct cpu *cpu, u8 value)
{
return 0;
}
static u8 shift_right(struct cpu *cpu, u8 value)
{
return 0;
}
static u8 swap(struct cpu *cpu, u8 value)
{
return ((value & 0xf0) >> 4) | ((value & 0x0f) << 4);
}
static void xor(struct cpu *regs, u8 value)
@ -223,15 +240,21 @@ static void subtract(struct cpu *cpu, u8 value, int with_carry, int just_compare
static void push(struct cpu *cpu, u16 value)
{
write16(cpu, cpu->sp - 2, value & 0xff);
write16(cpu, cpu->sp - 1, value >> 8);
printf("sp=%04x\n", cpu->sp);
printf("memory[sp-2] = %02x\n", value & 0xff);
printf("memory[sp-1] = %02x\n", value >> 8);
write8(cpu, cpu->sp - 2, value & 0xff);
write8(cpu, cpu->sp - 1, value >> 8);
cpu->sp -= 2;
}
static u16 pop(struct cpu *cpu)
{
cpu->sp += 2;
return read16(cpu, cpu->sp - 1) << 8 | read16(cpu, cpu->sp - 2);
printf("sp=%04x\n", cpu->sp);
printf("read memory[sp-2] = %02x\n", read8(cpu, cpu->sp - 2));
printf("read memory[sp-1] = %02x\n", read8(cpu, cpu->sp - 1));
return read8(cpu, cpu->sp - 1) << 8 | read8(cpu, cpu->sp - 2);
}
static void add16(struct cpu *cpu, u16 src)
@ -290,8 +313,20 @@ static void extended_insn(struct cpu *cpu, u8 insn)
int bit = (insn >> 3) & 0x7;
int reg = insn & 0x7;
u8 (*funcs[8])(struct cpu *, u8) = {
rotate_left,
rotate_right,
rotate_left, // TODO non-carry version
rotate_right,
shift_left,
shift_right,
swap,
shift_right // TODO SRL
};
switch (op) {
case 0:
write_reg(cpu, reg, funcs[bit](cpu, read_reg(cpu, reg)));
break;
case 1: // BIT
temp = read_reg(cpu, reg);
@ -332,7 +367,7 @@ void cpu_step(struct cpu *cpu)
cpu->pc += 2;
break;
case 0x07: // RLCA
rotate_left(cpu, &cpu->a);
cpu->a = rotate_left(cpu, cpu->a);
break;
case 0x08: // LD (a16),SP
write16(cpu, read16(cpu, cpu->pc), cpu->sp);
@ -341,8 +376,11 @@ void cpu_step(struct cpu *cpu)
case 0x19: // ADD HL,DE
add16(cpu, read_de(cpu));
break;
case 0x17: // RLA
cpu->a = rotate_left(cpu, cpu->a);
break;
case 0x1f: // RRA
rotate_right(cpu, &cpu->a);
cpu->a = rotate_right(cpu, cpu->a);
break;
// incs and decs
@ -481,7 +519,7 @@ void cpu_step(struct cpu *cpu)
case 0x20: // JR NZ,r8
temp = read8(cpu, cpu->pc);
if (!flag_isset(cpu, FLAG_ZERO)) {
cpu->pc += *((signed char *) &temp);
cpu->pc += *((signed char *) &temp) + 1;
} else {
cpu->pc++;
}
@ -500,6 +538,10 @@ void cpu_step(struct cpu *cpu)
cpu->sp = read16(cpu, cpu->pc);
cpu->pc += 2;
break;
case 0x22: // LD (HL+), A
write8(cpu, read_hl(cpu), cpu->a);
write_hl(cpu, read_hl(cpu) + 1);
break;
case 0x32: // LD (HL-), A
write8(cpu, read_hl(cpu), cpu->a);
write_hl(cpu, read_hl(cpu) - 1);
@ -613,6 +655,12 @@ void cpu_step(struct cpu *cpu)
case 0xf7: push(cpu, cpu->pc); cpu->pc = 0x30; break;
case 0xff: push(cpu, cpu->pc); cpu->pc = 0x38; break;
case 0xc1: // POP BC
write_bc(cpu, pop(cpu));
break;
case 0xc5: // PUSH BC
push(cpu, read_bc(cpu));
break;
case 0xcb:
extended_insn(cpu, read8(cpu, cpu->pc));
cpu->pc++;
@ -626,7 +674,7 @@ void cpu_step(struct cpu *cpu)
cpu->pc++;
break;
case 0xe2: // LD (C),A
write8(cpu, cpu->c, cpu->a);
write8(cpu, 0xff00 + cpu->c, cpu->a);
break;
case 0xea: // LD (a16),A
write16(cpu, read16(cpu, cpu->pc), cpu->a);
@ -641,6 +689,9 @@ void cpu_step(struct cpu *cpu)
}
cpu->pc++;
break;
case 0xf2: // LD A,(C)
cpu->a = read8(cpu, 0xff00 + cpu->c);
break;
case 0xf3: // DI
break;
case 0xfb: // EI

7
src/dmg.c
View File

@ -15,6 +15,9 @@ void dmg_new(struct dmg *dmg, struct cpu *cpu, struct rom *rom)
u8 dmg_read(void *_dmg, u16 address)
{
struct dmg *dmg = (struct dmg *) _dmg;
if (address < 0x100) {
return dmg_boot_rom[address];
}
if (address < 0x4000) {
return dmg->rom->data[address];
} else if (address < 0x8000) {
@ -27,6 +30,8 @@ u8 dmg_read(void *_dmg, u16 address)
return 0;
} else if (address < 0xe000) {
return dmg->main_ram[address - 0xc000];
} else if (address >= 0xff80 && address <= 0xfffe) {
return dmg->zero_page[address - 0xff80];
} else {
// not sure about any of this yet
return 0;
@ -49,6 +54,8 @@ void dmg_write(void *_dmg, u16 address, u8 data)
// TODO switchable ram bank
} else if (address < 0xe000) {
dmg->main_ram[address - 0xc000] = data;
} else if (address >= 0xff80 && address <= 0xfffe) {
dmg->zero_page[address - 0xff80] = data;
} else {
// not sure about any of this yet
}

2
src/dmg.h
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@ -7,8 +7,10 @@
struct dmg {
struct cpu *cpu;
struct rom *rom;
struct lcd *lcd;
u8 main_ram[0x2000];
u8 video_ram[0x2000];
u8 zero_page[0x80];
};
void dmg_new(struct dmg *dmg, struct cpu *cpu, struct rom *rom);

13
src/lcd.c Normal file
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@ -0,0 +1,13 @@
#include <stdio.h>
#include "types.h"
#include "lcd.h"
void lcd_put_pixel(struct lcd *lcd, u8 x, u8 y, u8 value)
{
if (x >= LCD_WIDTH || y >= LCD_HEIGHT) {
printf("warning: trying to write to (%d, %d) outside of lcd bounds\n", x, y);
return;
}
lcd->pixels[y * LCD_WIDTH + x] = value;
}

15
src/lcd.h Normal file
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@ -0,0 +1,15 @@
#ifndef _LCD_H
#define _LCD_H
#include "types.h"
#define LCD_WIDTH 160
#define LCD_HEIGHT 144
struct lcd {
u8 *pixels;
};
void lcd_put_pixel(struct lcd *lcd, u8 x, u8 y, u8 value);
#endif

5
src/main.c
View File

@ -9,6 +9,7 @@ int main(int argc, char *argv[])
struct cpu cpu;
struct rom rom;
struct dmg dmg;
int executed = 0;
if (argc < 2) {
printf("no rom specified\n");
@ -26,9 +27,9 @@ int main(int argc, char *argv[])
dmg_new(&dmg, &cpu, &rom);
cpu_bind_mem_model(&cpu, &dmg, dmg_read, dmg_write);
cpu.pc = 0x100;
cpu.pc = 0;
while (1) {
for (; executed < 100000; executed++) {
cpu_step(&cpu);
}