Macintosh-Tools
/
gb6
mirror of https://github.com/mlaux/gb6.git
1
0
Fork 0
Code Issues Projects Releases Wiki Activity

it would help if it would actually write to memory

This commit is contained in:
Matt Laux 2019-04-19 00:00:24 -05:00
parent 160e28fe6d
commit 79c42f6397
2 changed files with 49 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

33
src/cpu.c
View File

@ -188,11 +188,30 @@ static u16 pop(struct cpu *cpu)
return read16(cpu, cpu->sp - 1) << 8 | read16(cpu, cpu->sp - 2);
}
static u16 add16(struct cpu *cpu, u16 src)
{
clear_flag(cpu, FLAG_SIGN);
int total = read_hl(cpu) + src; // promoted to int
if (total > 0xffff) {
set_flag(cpu, FLAG_CARRY);
} else {
clear_flag(cpu, FLAG_CARRY);
}
if (((cpu->h & 0xf) + ((src >> 8) & 0xf)) & 0x10) {
// true if carry from bit 11 to bit 12
set_flag(cpu, FLAG_HALF_CARRY);
} else {
clear_flag(cpu, FLAG_HALF_CARRY);
}
return total & 0xffff;
}
void cpu_step(struct cpu *cpu)
{
u8 temp;
u8 opc = cpu->mem_read(cpu->mem_model, cpu->pc);
printf("0x%04x %s\n", cpu->pc, instructions[opc].format);
cpu->pc++;
switch (opc) {
case 0: // NOP
@ -344,6 +363,9 @@ void cpu_step(struct cpu *cpu)
write_hl(cpu, read16(cpu, cpu->pc));
cpu->pc += 2;
break;
case 0x29: // ADD HL,HL
add16(cpu, read_hl(cpu));
break;
case 0x31: // LD SP,d16
cpu->sp = read16(cpu, cpu->pc);
cpu->pc += 2;
@ -355,6 +377,14 @@ void cpu_step(struct cpu *cpu)
case 0x94:
subtract(cpu, cpu->h);
break;
case 0xc0: // RET NZ
if (!flag_isset(cpu, FLAG_ZERO)) {
cpu->pc = pop(cpu);
}
break;
case 0xc9: // RET
cpu->pc = pop(cpu);
break;
case 0xcd: // CALL a16
temp = read16(cpu, cpu->pc);
cpu->pc += 2;
@ -397,7 +427,6 @@ void cpu_step(struct cpu *cpu)
cpu->pc++;
break;
case 0xf3: // DI
printf("disable interrupts\n");
break;
default:
printf("unknown opcode 0x%02x %s\n", opc, instructions[opc].format);

18
src/dmg.c
View File

@ -1,3 +1,5 @@
#include <stdio.h>
#include "cpu.h"
#include "rom.h"
#include "dmg.h"
@ -33,4 +35,20 @@ u8 dmg_read(void *_dmg, u16 address)
void dmg_write(void *_dmg, u16 address, u8 data)
{
struct dmg *dmg = (struct dmg *) _dmg;
if (address < 0x4000) {
printf("warning: writing 0x%04x in rom\n", address);
dmg->rom->data[address] = data;
} else if (address < 0x8000) {
// TODO switchable rom bank
printf("warning: writing 0x%04x in rom\n", address);
dmg->rom->data[address] = data;
} else if (address < 0xa000) {
dmg->video_ram[address - 0x8000] = data;
} else if (address < 0xc000) {
// TODO switchable ram bank
} else if (address < 0xe000) {
dmg->main_ram[address - 0xc000] = data;
} else {
// not sure about any of this yet
}
}