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Diffstat (limited to '6502/src/6502.c')
-rw-r--r--6502/src/6502.c197
1 files changed, 86 insertions, 111 deletions
diff --git a/6502/src/6502.c b/6502/src/6502.c
index c9b802d..add78a0 100644
--- a/6502/src/6502.c
+++ b/6502/src/6502.c
@@ -15,162 +15,137 @@ void l6502_mem_basic_new(l6502_mem *m) {
m->data = calloc(1 << 16, sizeof(u8));
}
-static u8 l6502_flag_get(l6502_emu *e, l6502_flag f) { return (e->regs.flags & (u8) f) != 0; }
-static void l6502_flag_set(l6502_emu *e, l6502_flag f, u8 v) {
- if (v) e->regs.flags |= (u8) f;
- else e->regs.flags &= ~((u8) f);
-}
-static void l6502_flags_check_zn(l6502_emu *e, u8 v) {
+static void flags_check_zn(l6502_emu *e, u8 v) {
l6502_flag_set(e, L6502_FLAG_ZERO, v == 0);
l6502_flag_set(e, L6502_FLAG_NEGATIVE, (v >> 7) & 0b1);
}
-static u8 l6502_read(l6502_emu *e, u16 addr) { return e->mem.rh(e->mem.data, addr); }
-static void l6502_write(l6502_emu *e, u16 addr, u8 val) { e->mem.wh(e->mem.data, addr, val); }
-static u16 l6502_read_addr(l6502_emu *e, u16 addr) {
- u8 alo = l6502_read(e, addr);
- u8 ahi = l6502_read(e, addr + 1);
- return ahi << 8 | alo;
-}
-
-static u8 l6502_pop(l6502_emu *e) { return l6502_read(e, 0x0100 + (u16) ++e->regs.sp); }
-static void l6502_push(l6502_emu *e, u8 val) { l6502_write(e, 0x0100 + (u16) e->regs.sp--, val); }
-static u16 l6502_pop_addr(l6502_emu *e) {
- u8 ahi = l6502_pop(e);
- u8 alo = l6502_pop(e);
- return ahi << 8 | alo;
-}
-static void l6502_push_addr(l6502_emu *e, u16 addr) {
- l6502_push(e, (u8) (addr & 0xff));
- l6502_push(e, (u8) (addr >> 8));
-}
-
-static u16 l6502_addressing_mode_immediate(l6502_emu *e) {
- return e->regs.pc++;
+static u16 amode_immediate(l6502_emu *e) {
+ return e->pc++;
}
-static u16 l6502_addressing_mode_absolute(l6502_emu *e) {
- u16 addr = l6502_read_addr(e, e->regs.pc);
- e->regs.pc += 2;
+static u16 amode_absolute(l6502_emu *e) {
+ u16 addr = l6502_read_addr(e, e->pc);
+ e->pc += 2;
return addr;
}
-static u16 l6502_addressing_mode_absolute_x(l6502_emu *e) {
- u16 addr = l6502_read_addr(e, e->regs.pc) + (u16) e->regs.x;
- e->regs.pc += 2;
+static u16 amode_absolute_x(l6502_emu *e) {
+ u16 addr = l6502_read_addr(e, e->pc) + (u16) e->regs[L6502_REG_X];
+ e->pc += 2;
return addr;
}
-static u16 l6502_addressing_mode_absolute_y(l6502_emu *e) {
- u16 addr = l6502_read_addr(e, e->regs.pc) + (u16) e->regs.y;
- e->regs.pc += 2;
+static u16 amode_absolute_y(l6502_emu *e) {
+ u16 addr = l6502_read_addr(e, e->pc) + (u16) e->regs[L6502_REG_Y];
+ e->pc += 2;
return addr;
}
-static u16 l6502_addressing_mode_zeropage(l6502_emu *e) {
- return (u16) l6502_read(e, e->regs.pc++);
+static u16 amode_zeropage(l6502_emu *e) {
+ return (u16) l6502_read(e, e->pc++);
}
-static u16 l6502_addressing_mode_zeropage_x(l6502_emu *e) {
- return (u16) (l6502_read(e, e->regs.pc++) + e->regs.x);
+static u16 amode_zeropage_x(l6502_emu *e) {
+ return (u16) (l6502_read(e, e->pc++) + e->regs[L6502_REG_X]);
}
-static u16 l6502_addressing_mode_indirect_zeropage_x(l6502_emu *e) {
- return l6502_read_addr(e, l6502_read(e, e->regs.pc++) + e->regs.x);
+static u16 amode_indirect_zeropage_x(l6502_emu *e) {
+ return l6502_read_addr(e, l6502_read(e, e->pc++) + (u16) e->regs[L6502_REG_X]);
}
-static u16 l6502_addressing_mode_indirect_zeropage_y(l6502_emu *e) {
- return l6502_read_addr(e, l6502_read(e, e->regs.pc++)) + (u16) e->regs.y;
+static u16 amode_indirect_zeropage_y(l6502_emu *e) {
+ return l6502_read_addr(e, l6502_read(e, e->pc++)) + (u16) e->regs[L6502_REG_Y];
}
void l6502_emulate(l6502_emu *e) {
- u8 ins = l6502_read(e, e->regs.pc++);
+ u8 ins = l6502_read(e, e->pc++);
u8 val = 0;
u16 res = 0;
bool set_flags = true;
bool set_result = true;
- u8 *set_reg = NULL;
+ l6502_reg set_reg = L6502_REG__MARKER;
u16 addr = 0;
switch (ins) { /* identify some special-case instructions */
case BRK:
- l6502_push_addr(e, e->regs.pc);
- l6502_push(e, e->regs.flags);
- e->regs.pc = l6502_read_addr(e, 0xfffe);
+ l6502_push_addr(e, e->pc);
+ l6502_push(e, e->regs[L6502_REG_FLAGS]);
+ e->pc = l6502_read_addr(e, 0xfffe);
l6502_flag_set(e, L6502_FLAG_BREAK_COMMAND, true);
break;
- case PHP: l6502_push(e, e->regs.flags); break;
+ case PHP: l6502_push(e, e->regs[L6502_REG_FLAGS]); break;
case CLC: l6502_flag_set(e, L6502_FLAG_CARRY, false); break;
case JSR:
- addr = l6502_read_addr(e, e->regs.pc);
- l6502_push_addr(e, e->regs.pc + 1);
- e->regs.pc = addr;
+ addr = l6502_read_addr(e, e->pc);
+ l6502_push_addr(e, e->pc + 1);
+ e->pc = addr;
break;
- case PLP: e->regs.flags = l6502_pop(e); break;
+ case PLP: e->regs[L6502_REG_FLAGS] = l6502_pop(e); break;
case SEC: l6502_flag_set(e, L6502_FLAG_CARRY, true); break;
case RTI:
- e->regs.flags = l6502_pop(e);
- e->regs.pc = l6502_pop_addr(e);
+ e->regs[L6502_REG_FLAGS] = l6502_pop(e);
+ e->pc = l6502_pop_addr(e);
break;
- case PHA: l6502_push(e, e->regs.a); break;
+ case PHA: l6502_push(e, e->regs[L6502_REG_A]); break;
case JMP_ABSOLUTE:
- addr = l6502_read_addr(e, e->regs.pc);
- e->regs.pc = addr;
+ addr = l6502_read_addr(e, e->pc);
+ e->pc = addr;
break;
case CLI: l6502_flag_set(e, L6502_FLAG_INTERRUPT_DISABLE, false); break;
- case RTS: e->regs.pc = l6502_pop_addr(e) + 1; break;
- case PLA: e->regs.a = l6502_pop(e); break;
+ case RTS: e->pc = l6502_pop_addr(e) + 1; break;
+ case PLA: e->regs[L6502_REG_A] = l6502_pop(e); break;
case JMP_INDIRECT:
- addr = l6502_read_addr(e, l6502_read_addr(e, e->regs.pc));
- e->regs.pc = addr;
+ addr = l6502_read_addr(e, l6502_read_addr(e, e->pc));
+ e->pc = addr;
break;
case SEI: l6502_flag_set(e, L6502_FLAG_INTERRUPT_DISABLE, true); break;
- case DEY: e->regs.y -= 1; l6502_flags_check_zn(e, e->regs.y); break;
- case TXA: e->regs.a = e->regs.x; l6502_flags_check_zn(e, e->regs.a); break;
- case TYA: e->regs.a = e->regs.y; l6502_flags_check_zn(e, e->regs.a); break;
- case TXS: e->regs.sp = e->regs.x; break; /* note TXS does not set flags */
- case TAY: e->regs.y = e->regs.a; l6502_flags_check_zn(e, e->regs.y); break;
- case TAX: e->regs.x = e->regs.a; l6502_flags_check_zn(e, e->regs.x); break;
+ case DEY: e->regs[L6502_REG_Y] -= 1; flags_check_zn(e, e->regs[L6502_REG_Y]); break;
+ case TXA: e->regs[L6502_REG_A] = e->regs[L6502_REG_X]; flags_check_zn(e, e->regs[L6502_REG_A]); break;
+ case TYA: e->regs[L6502_REG_A] = e->regs[L6502_REG_Y]; flags_check_zn(e, e->regs[L6502_REG_A]); break;
+ case TXS: e->regs[L6502_REG_SP] = e->regs[L6502_REG_X]; break; /* note TXS does not set flags */
+ case TAY: e->regs[L6502_REG_Y] = e->regs[L6502_REG_A]; flags_check_zn(e, e->regs[L6502_REG_Y]); break;
+ case TAX: e->regs[L6502_REG_X] = e->regs[L6502_REG_A]; flags_check_zn(e, e->regs[L6502_REG_X]); break;
case CLV: l6502_flag_set(e, L6502_FLAG_OVERFLOW, false); break;
- case TSX: e->regs.x = e->regs.sp; l6502_flags_check_zn(e, e->regs.x); break;
- case INY: e->regs.y += 1; l6502_flags_check_zn(e, e->regs.y); break;
- case DEX: e->regs.x -= 1; l6502_flags_check_zn(e, e->regs.x); break;
+ case TSX: e->regs[L6502_REG_X] = e->regs[L6502_REG_SP]; flags_check_zn(e, e->regs[L6502_REG_X]); break;
+ case INY: e->regs[L6502_REG_Y] += 1; flags_check_zn(e, e->regs[L6502_REG_Y]); break;
+ case DEX: e->regs[L6502_REG_X] -= 1; flags_check_zn(e, e->regs[L6502_REG_X]); break;
case CLD: l6502_flag_set(e, L6502_FLAG_DECIMAL, false); break;
- case INX: e->regs.x += 1; l6502_flags_check_zn(e, e->regs.x); break;
+ case INX: e->regs[L6502_REG_X] += 1; flags_check_zn(e, e->regs[L6502_REG_X]); break;
case NOP: break;
case SED: l6502_flag_set(e, L6502_FLAG_DECIMAL, true); break;
}
if ((ins & 0b11111) == 0b10000) { /* identify conditional branches */
l6502_flag flags[4] = { L6502_FLAG_NEGATIVE, L6502_FLAG_OVERFLOW, L6502_FLAG_CARRY, L6502_FLAG_ZERO };
- u8 off = l6502_read(e, e->regs.pc++);
+ u8 off = l6502_read(e, e->pc++);
if (l6502_flag_get(e, flags[(ins >> 6) & 0b11]) == ((ins >> 5) & 0b1)) {
- e->regs.pc = (u16) ((i16) e->regs.pc + (i16) (i8) off);
+ e->pc = (u16) ((i16) e->pc + (i16) (i8) off);
}
return;
}
switch (ins & 0b11) { /* identify instructions in common forms */
case 0b01: { /* group one */
- set_reg = &e->regs.a;
+ set_reg = L6502_REG_A;
switch ((ins >> 2) & 0b111) {
- case G1_ADDRESSING_MODE_INDIRECT_ZEROPAGE_X: addr = l6502_addressing_mode_indirect_zeropage_x(e); break;
- case G1_ADDRESSING_MODE_ZEROPAGE: addr = l6502_addressing_mode_zeropage(e); break;
- case G1_ADDRESSING_MODE_IMMEDIATE: addr = l6502_addressing_mode_immediate(e); break;
- case G1_ADDRESSING_MODE_ABSOLUTE: addr = l6502_addressing_mode_absolute(e); break;
- case G1_ADDRESSING_MODE_INDIRECT_ZEROPAGE_Y: addr = l6502_addressing_mode_indirect_zeropage_y(e); break;
- case G1_ADDRESSING_MODE_ZEROPAGE_X: addr = l6502_addressing_mode_zeropage_x(e); break;
- case G1_ADDRESSING_MODE_ABSOLUTE_Y: addr = l6502_addressing_mode_absolute_y(e); break;
- case G1_ADDRESSING_MODE_ABSOLUTE_X: addr = l6502_addressing_mode_absolute_x(e); break;
+ case G1_ADDRESSING_MODE_INDIRECT_ZEROPAGE_X: addr = amode_indirect_zeropage_x(e); break;
+ case G1_ADDRESSING_MODE_ZEROPAGE: addr = amode_zeropage(e); break;
+ case G1_ADDRESSING_MODE_IMMEDIATE: addr = amode_immediate(e); break;
+ case G1_ADDRESSING_MODE_ABSOLUTE: addr = amode_absolute(e); break;
+ case G1_ADDRESSING_MODE_INDIRECT_ZEROPAGE_Y: addr = amode_indirect_zeropage_y(e); break;
+ case G1_ADDRESSING_MODE_ZEROPAGE_X: addr = amode_zeropage_x(e); break;
+ case G1_ADDRESSING_MODE_ABSOLUTE_Y: addr = amode_absolute_y(e); break;
+ case G1_ADDRESSING_MODE_ABSOLUTE_X: addr = amode_absolute_x(e); break;
}
val = l6502_read(e, addr);
switch ((ins >> 5) & 0b111) {
- case G1_OPCODE_ORA: res = (u16) e->regs.a | (u16) val; break;
- case G1_OPCODE_AND: res = (u16) e->regs.a & (u16) val; break;
- case G1_OPCODE_EOR: res = (u16) e->regs.a ^ (u16) val; break;
+ case G1_OPCODE_ORA: res = (u16) e->regs[L6502_REG_A] | (u16) val; break;
+ case G1_OPCODE_AND: res = (u16) e->regs[L6502_REG_A] & (u16) val; break;
+ case G1_OPCODE_EOR: res = (u16) e->regs[L6502_REG_A] ^ (u16) val; break;
case G1_OPCODE_ADC:
- res = (u16) e->regs.a + (u16) val;
+ res = (u16) e->regs[L6502_REG_A] + (u16) val;
res += (u16) l6502_flag_get(e, L6502_FLAG_CARRY);
l6502_flag_set(e, L6502_FLAG_OVERFLOW, ((res >> 8) != 0) != ((res >> 7) & 0b1));
break;
- case G1_OPCODE_STA: l6502_write(e, addr, e->regs.a); set_flags = set_result = false; break;
+ case G1_OPCODE_STA: l6502_write(e, addr, e->regs[L6502_REG_A]); set_flags = set_result = false; break;
case G1_OPCODE_LDA: res = (u16) l6502_read(e, addr); break;
case G1_OPCODE_CMP:
set_result = false;
- res = (u16) e->regs.a - (u16) val;
+ res = (u16) e->regs[L6502_REG_A] - (u16) val;
break;
case G1_OPCODE_SBC:
- res = (u16) e->regs.a - (u16) val;
+ res = (u16) e->regs[L6502_REG_A] - (u16) val;
res -= (u16) (1 - l6502_flag_get(e, L6502_FLAG_CARRY));
l6502_flag_set(e, L6502_FLAG_OVERFLOW, ((res >> 8) != 0) != ((res >> 7) & 0b1));
break;
@@ -179,12 +154,12 @@ void l6502_emulate(l6502_emu *e) {
}
case 0b10: { /* group two */
switch ((ins >> 2) & 0b111) {
- case G2_ADDRESSING_MODE_IMMEDIATE: addr = l6502_addressing_mode_immediate(e); break;
- case G2_ADDRESSING_MODE_ZEROPAGE: addr = l6502_addressing_mode_zeropage(e); break;
- case G2_ADDRESSING_MODE_ACCUMULATOR: addr = (u16) e->regs.a; set_reg = &e->regs.a; break;
- case G2_ADDRESSING_MODE_ABSOLUTE: addr = l6502_addressing_mode_absolute(e); break;
- case G2_ADDRESSING_MODE_ZEROPAGE_X: addr = l6502_addressing_mode_zeropage_x(e); break;
- case G2_ADDRESSING_MODE_ABSOLUTE_X: addr = l6502_addressing_mode_absolute_x(e); break;
+ case G2_ADDRESSING_MODE_IMMEDIATE: addr = amode_immediate(e); break;
+ case G2_ADDRESSING_MODE_ZEROPAGE: addr = amode_zeropage(e); break;
+ case G2_ADDRESSING_MODE_ACCUMULATOR: addr = (u16) e->regs[L6502_REG_A]; set_reg = L6502_REG_A; break;
+ case G2_ADDRESSING_MODE_ABSOLUTE: addr = amode_absolute(e); break;
+ case G2_ADDRESSING_MODE_ZEROPAGE_X: addr = amode_zeropage_x(e); break;
+ case G2_ADDRESSING_MODE_ABSOLUTE_X: addr = amode_absolute_x(e); break;
}
val = set_reg ? (u8) addr : l6502_read(e, addr);
switch ((ins >> 5) & 0b111) {
@@ -199,8 +174,8 @@ void l6502_emulate(l6502_emu *e) {
| (u16) l6502_flag_get(e, L6502_FLAG_CARRY) << 7
| (u16) (val & 0b1) << 8; /* same as above */
break;
- case G2_OPCODE_STX: l6502_write(e, addr, e->regs.x); set_flags = set_result = false; break;
- case G2_OPCODE_LDX: res = (u16) l6502_read(e, addr); set_reg = &e->regs.x; break;
+ case G2_OPCODE_STX: l6502_write(e, addr, e->regs[L6502_REG_X]); set_flags = set_result = false; break;
+ case G2_OPCODE_LDX: res = (u16) l6502_read(e, addr); set_reg = L6502_REG_X; break;
case G2_OPCODE_DEC: res = (u16) val - 1; break;
case G2_OPCODE_INC: res = (u16) val + 1; break;
}
@@ -208,29 +183,29 @@ void l6502_emulate(l6502_emu *e) {
}
case 0b00: { /* group three */
switch ((ins >> 2) & 0b111) {
- case G3_ADDRESSING_MODE_IMMEDIATE: addr = l6502_addressing_mode_immediate(e); break;
- case G3_ADDRESSING_MODE_ZEROPAGE: addr = l6502_addressing_mode_zeropage(e); break;
- case G3_ADDRESSING_MODE_ABSOLUTE: addr = l6502_addressing_mode_absolute(e); break;
- case G3_ADDRESSING_MODE_ZEROPAGE_X: addr = l6502_addressing_mode_zeropage_x(e); break;
- case G3_ADDRESSING_MODE_ABSOLUTE_X: addr = l6502_addressing_mode_absolute_x(e); break;
+ case G3_ADDRESSING_MODE_IMMEDIATE: addr = amode_immediate(e); break;
+ case G3_ADDRESSING_MODE_ZEROPAGE: addr = amode_zeropage(e); break;
+ case G3_ADDRESSING_MODE_ABSOLUTE: addr = amode_absolute(e); break;
+ case G3_ADDRESSING_MODE_ZEROPAGE_X: addr = amode_zeropage_x(e); break;
+ case G3_ADDRESSING_MODE_ABSOLUTE_X: addr = amode_absolute_x(e); break;
}
val = l6502_read(e, addr);
switch ((ins >> 5) & 0b111) {
case G3_OPCODE_BIT:
set_flags = set_result = false;
- l6502_flag_set(e, L6502_FLAG_ZERO, (e->regs.a & val) == 0);
+ l6502_flag_set(e, L6502_FLAG_ZERO, (e->regs[L6502_REG_A] & val) == 0);
l6502_flag_set(e, L6502_FLAG_OVERFLOW, (val >> 6) & 0b1);
l6502_flag_set(e, L6502_FLAG_NEGATIVE, (val >> 7) & 0b1);
break;
- case G3_OPCODE_STY: l6502_write(e, addr, e->regs.y); set_flags = set_result = false; break;
- case G3_OPCODE_LDY: res = (u16) l6502_read(e, addr); set_reg = &e->regs.y; break;
+ case G3_OPCODE_STY: l6502_write(e, addr, e->regs[L6502_REG_Y]); set_flags = set_result = false; break;
+ case G3_OPCODE_LDY: res = (u16) l6502_read(e, addr); set_reg = L6502_REG_Y; break;
case G3_OPCODE_CPY:
set_result = false;
- res = (u16) e->regs.y - (u16) val;
+ res = (u16) e->regs[L6502_REG_Y] - (u16) val;
break;
case G3_OPCODE_CPX:
set_result = false;
- res = (u16) e->regs.x - (u16) val;
+ res = (u16) e->regs[L6502_REG_X] - (u16) val;
break;
}
}
@@ -241,7 +216,7 @@ void l6502_emulate(l6502_emu *e) {
l6502_flag_set(e, L6502_FLAG_CARRY, (res >> 8) != 0);
}
if (set_result) {
- if (set_reg) *set_reg = (u8) res;
+ if (set_reg != L6502_REG__MARKER) e->regs[set_reg] = (u8) res;
else l6502_write(e, addr, (u8) res);
}
}
generated by cgit v1.3.1 (git 2.54.0) at 2026-09-02 02:52:25 +0000