From ca8daa96caed9d53db95336bad917d2e03e7b00f Mon Sep 17 00:00:00 2001 From: LLLL Colonq Date: Sat, 11 Jul 2026 00:34:23 -0400 Subject: 6502: All tests pass! --- 6502/src/6502.c | 200 ++++++++++++++++++++++++++++++++++++-------------------- 6502/src/test.c | 4 +- 2 files changed, 133 insertions(+), 71 deletions(-) (limited to '6502/src') diff --git a/6502/src/6502.c b/6502/src/6502.c index 54013ae..eb0f2c0 100644 --- a/6502/src/6502.c +++ b/6502/src/6502.c @@ -2,6 +2,7 @@ #include #include +#include static u8 basic_read_handler(void *data, u16 addr) { return ((u8 *) data)[addr]; @@ -42,79 +43,94 @@ static u16 amode_zeropage(l6502_emu *e) { return (u16) l6502_read(e, e->pc++); } static u16 amode_zeropage_x(l6502_emu *e) { - return (u16) (l6502_read(e, e->pc++) + e->regs[L6502_REG_X]); + return (u16) (u8) (l6502_read(e, e->pc++) + e->regs[L6502_REG_X]); +} +static u16 amode_zeropage_y(l6502_emu *e) { + return (u16) (u8) (l6502_read(e, e->pc++) + e->regs[L6502_REG_Y]); } 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]); + return l6502_read_addr_wrap_page(e, (u8) (l6502_read(e, e->pc++) + e->regs[L6502_REG_X])); } 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]; + return l6502_read_addr_wrap_page(e, l6502_read(e, e->pc++)) + (u16) e->regs[L6502_REG_Y]; } -void l6502_emulate(l6502_emu *e) { +const char *l6502_emulate(l6502_emu *e) { u8 ins = l6502_read(e, e->pc++); u8 val = 0; u16 res = 0; bool set_flags = true; + bool set_carry = false; bool set_result = true; l6502_reg set_reg = L6502_REG__MARKER; u16 addr = 0; + const char *nm = NULL; + switch (ins) { /* identify some special-case instructions */ case BRK: - l6502_push_addr(e, e->pc); - l6502_push(e, e->regs[L6502_REG_FLAGS]); - e->pc = l6502_read_addr(e, 0xfffe) - 1; - l6502_flag_set(e, L6502_FLAG_BREAK_COMMAND, true); - 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->pc); + nm = "brk"; l6502_push_addr(e, e->pc + 1); - e->pc = addr; - break; - case PLP: e->regs[L6502_REG_FLAGS] = l6502_pop(e); break; - case SEC: l6502_flag_set(e, L6502_FLAG_CARRY, true); break; + l6502_push(e, e->regs[L6502_REG_FLAGS] | L6502_FLAG_BREAK_COMMAND); + e->pc = l6502_read_addr(e, 0xfffe); + l6502_flag_set(e, L6502_FLAG_INTERRUPT_DISABLE, true); + return nm; + case PHP: nm = "php"; l6502_push(e, e->regs[L6502_REG_FLAGS] | L6502_FLAG_BREAK_COMMAND | L6502_FLAG_UNUSED); return nm; + case CLC: nm = "clc"; l6502_flag_set(e, L6502_FLAG_CARRY, false); return nm; + case JSR: { + nm = "jsr"; + u16 alo = l6502_read(e, e->pc); + l6502_push_addr(e, e->pc + 1); + u16 ahi = l6502_read(e, e->pc + 1); + e->pc = ahi << 8 | alo; + return nm; + } + case PLP: nm = "plp"; e->regs[L6502_REG_FLAGS] = l6502_pop(e) & (u8) ~L6502_FLAG_BREAK_COMMAND; return nm; + case SEC: nm = "sec"; l6502_flag_set(e, L6502_FLAG_CARRY, true); return nm; case RTI: - e->regs[L6502_REG_FLAGS] = l6502_pop(e); + nm = "rti"; + e->regs[L6502_REG_FLAGS] = l6502_pop(e) & (u8) ~L6502_FLAG_BREAK_COMMAND; e->pc = l6502_pop_addr(e); - break; - case PHA: l6502_push(e, e->regs[L6502_REG_A]); break; + return nm; + case PHA: nm = "pha"; l6502_push(e, e->regs[L6502_REG_A]); return nm; case JMP_ABSOLUTE: + nm = "jmp"; 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->pc = l6502_pop_addr(e) + 1; break; - case PLA: e->regs[L6502_REG_A] = l6502_pop(e); break; + return nm; + case CLI: nm = "cli"; l6502_flag_set(e, L6502_FLAG_INTERRUPT_DISABLE, false); return nm; + case RTS: nm = "rts"; e->pc = l6502_pop_addr(e) + 1; return nm; + case PLA: nm = "pla"; e->regs[L6502_REG_A] = l6502_pop(e); flags_check_zn(e, e->regs[L6502_REG_A]); return nm; case JMP_INDIRECT: - addr = l6502_read_addr(e, l6502_read_addr(e, e->pc)); + nm = "jmp"; + addr = l6502_read_addr_wrap_page(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[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[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[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; + return nm; + case SEI: nm = "sei"; l6502_flag_set(e, L6502_FLAG_INTERRUPT_DISABLE, true); return nm; + case DEY: nm = "dey"; e->regs[L6502_REG_Y] -= 1; flags_check_zn(e, e->regs[L6502_REG_Y]); return nm; + case TXA: nm = "txa"; e->regs[L6502_REG_A] = e->regs[L6502_REG_X]; flags_check_zn(e, e->regs[L6502_REG_A]); return nm; + case TYA: nm = "tya"; e->regs[L6502_REG_A] = e->regs[L6502_REG_Y]; flags_check_zn(e, e->regs[L6502_REG_A]); return nm; + case TXS: nm = "txs"; e->regs[L6502_REG_SP] = e->regs[L6502_REG_X]; return nm; /* note TXS does not set flags */ + case TAY: nm = "tay"; e->regs[L6502_REG_Y] = e->regs[L6502_REG_A]; flags_check_zn(e, e->regs[L6502_REG_Y]); return nm; + case TAX: nm = "tax"; e->regs[L6502_REG_X] = e->regs[L6502_REG_A]; flags_check_zn(e, e->regs[L6502_REG_X]); return nm; + case CLV: nm = "clv"; l6502_flag_set(e, L6502_FLAG_OVERFLOW, false); return nm; + case TSX: nm = "tsx"; e->regs[L6502_REG_X] = e->regs[L6502_REG_SP]; flags_check_zn(e, e->regs[L6502_REG_X]); return nm; + case INY: nm = "iny"; e->regs[L6502_REG_Y] += 1; flags_check_zn(e, e->regs[L6502_REG_Y]); return nm; + case DEX: nm = "dex"; e->regs[L6502_REG_X] -= 1; flags_check_zn(e, e->regs[L6502_REG_X]); return nm; + case CLD: nm = "cld"; l6502_flag_set(e, L6502_FLAG_DECIMAL, false); return nm; + case INX: nm = "inx"; e->regs[L6502_REG_X] += 1; flags_check_zn(e, e->regs[L6502_REG_X]); return nm; + case NOP: nm = "nop"; return nm; + case SED: nm = "sed"; l6502_flag_set(e, L6502_FLAG_DECIMAL, true); return nm; } + 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->pc++); if (l6502_flag_get(e, flags[(ins >> 6) & 0b11]) == ((ins >> 5) & 0b1)) { e->pc = (u16) ((i16) e->pc + (i16) (i8) off); } - return; + return "jcc"; } + switch (ins & 0b11) { /* identify instructions in common forms */ case 0b01: { /* group one */ set_reg = L6502_REG_A; @@ -130,24 +146,38 @@ void l6502_emulate(l6502_emu *e) { } val = l6502_read(e, addr); switch ((ins >> 5) & 0b111) { - 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[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)); + case G1_OPCODE_ORA: nm = "ora"; res = (u16) e->regs[L6502_REG_A] | (u16) val; break; + case G1_OPCODE_AND: nm = "and"; res = (u16) e->regs[L6502_REG_A] & (u16) val; break; + case G1_OPCODE_EOR: nm = "eor"; res = (u16) e->regs[L6502_REG_A] ^ (u16) val; break; + case G1_OPCODE_ADC: { + nm = "adc"; + set_carry = true; + i8 a0 = (i8) e->regs[L6502_REG_A]; + i8 a1 = (i8) val; + i8 a2 = (i8) l6502_flag_get(e, L6502_FLAG_CARRY); + res = (u16) (u8) a0 + (u16) (u8) a1; res += (u16) (u8) a2; + l6502_flag_set(e, L6502_FLAG_OVERFLOW, ((a0 >= 0) == (a1 >= 0)) && ((a0 >= 0) != ((i8) res >= 0))); 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_STA: nm = "sta"; l6502_write(e, addr, e->regs[L6502_REG_A]); set_flags = set_result = false; break; + case G1_OPCODE_LDA: nm = "lda"; res = (u16) l6502_read(e, addr); break; case G1_OPCODE_CMP: + nm = "cmp"; set_result = false; - res = (u16) e->regs[L6502_REG_A] - (u16) val; + set_carry = true; + res = (u16) (u8) (e->regs[L6502_REG_A] - val); + if (e->regs[L6502_REG_A] >= val) res |= 1 << 8; break; case G1_OPCODE_SBC: - 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)); + nm = "sbc"; + set_carry = true; + i8 a0 = (i8) e->regs[L6502_REG_A]; + i8 a1 = (i8) val; + i8 a2 = (i8) (1 - l6502_flag_get(e, L6502_FLAG_CARRY)); + res = (u16) (u8) a0 - (u16) (u8) a1; res -= (u16) (u8) a2; + res &= 0xff; + if ((u8) a0 >= (u8) a1 + (u8) a2) res |= 1 << 8; + l6502_flag_set(e, L6502_FLAG_OVERFLOW, !((a0 >= 0) == (a1 >= 0)) && ((a0 >= 0) != ((i8) res >= 0))); break; } break; @@ -158,26 +188,48 @@ void l6502_emulate(l6502_emu *e) { 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; + case G2_ADDRESSING_MODE_ZEROPAGE_X: + switch ((ins >> 5) & 0b111) { + case G2_OPCODE_LDX: case G2_OPCODE_STX: addr = amode_zeropage_y(e); break; + default: addr = amode_zeropage_x(e); break; + } + break; + case G2_ADDRESSING_MODE_ABSOLUTE_X: + switch ((ins >> 5) & 0b111) { + case G2_OPCODE_LDX: case G2_OPCODE_STX: addr = amode_absolute_y(e); break; + default: addr = amode_absolute_x(e); break; + } + break; } - val = set_reg ? (u8) addr : l6502_read(e, addr); + val = set_reg != L6502_REG__MARKER ? (u8) addr : l6502_read(e, addr); switch ((ins >> 5) & 0b111) { - case G2_OPCODE_ASL: res = ((u16) val) << 1; break; - case G2_OPCODE_ROL: res = ((u16) val) << 1 | (u16) l6502_flag_get(e, L6502_FLAG_CARRY); break; + case G2_OPCODE_ASL: + nm = "asl"; + set_carry = true; + res = ((u16) val) << 1; + break; + case G2_OPCODE_ROL: + nm = "rol"; + set_carry = true; + res = ((u16) val) << 1 | (u16) l6502_flag_get(e, L6502_FLAG_CARRY); + break; case G2_OPCODE_LSR: + nm = "lsr"; + set_carry = true; res = ((u16) val) >> 1 | (u16) (val & 0b1) << 8; /* place the previous low bit in carry */ break; case G2_OPCODE_ROR: + nm = "ror"; + set_carry = true; res = ((u16) val) >> 1 | (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[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; + case G2_OPCODE_STX: nm = "stx"; l6502_write(e, addr, e->regs[L6502_REG_X]); set_flags = set_result = false; break; + case G2_OPCODE_LDX: nm = "ldx"; res = (u16) l6502_read(e, addr); set_reg = L6502_REG_X; break; + case G2_OPCODE_DEC: nm = "dec"; res = (u16) val - 1; break; + case G2_OPCODE_INC: nm = "inc"; res = (u16) val + 1; break; } break; } @@ -192,31 +244,39 @@ void l6502_emulate(l6502_emu *e) { val = l6502_read(e, addr); switch ((ins >> 5) & 0b111) { case G3_OPCODE_BIT: + nm = "bit"; set_flags = set_result = false; 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[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_STY: nm = "sty"; l6502_write(e, addr, e->regs[L6502_REG_Y]); set_flags = set_result = false; break; + case G3_OPCODE_LDY: nm = "ldy"; res = (u16) l6502_read(e, addr); set_reg = L6502_REG_Y; break; case G3_OPCODE_CPY: + nm = "cpy"; set_result = false; - res = (u16) e->regs[L6502_REG_Y] - (u16) val; + set_carry = true; + res = (u16) (u8) (e->regs[L6502_REG_Y] - val); + if (e->regs[L6502_REG_Y] >= val) res |= 1 << 8; break; case G3_OPCODE_CPX: + nm = "cpx"; set_result = false; - res = (u16) e->regs[L6502_REG_X] - (u16) val; + set_carry = true; + res = (u16) (u8) (e->regs[L6502_REG_X] - val); + if (e->regs[L6502_REG_X] >= val) res |= 1 << 8; break; } } } if (set_flags) { - l6502_flag_set(e, L6502_FLAG_ZERO, res == 0); + l6502_flag_set(e, L6502_FLAG_ZERO, (res & 0xff) == 0); l6502_flag_set(e, L6502_FLAG_NEGATIVE, (res >> 7) & 0b1); - l6502_flag_set(e, L6502_FLAG_CARRY, (res >> 8) != 0); + if (set_carry) l6502_flag_set(e, L6502_FLAG_CARRY, (res >> 8) != 0); } if (set_result) { if (set_reg != L6502_REG__MARKER) e->regs[set_reg] = (u8) res; else l6502_write(e, addr, (u8) res); } + return nm; } diff --git a/6502/src/test.c b/6502/src/test.c index 1497df6..694108e 100644 --- a/6502/src/test.c +++ b/6502/src/test.c @@ -22,6 +22,7 @@ int emu_summary(lua_State *l) { lua_pushinteger(l, e->regs[L6502_REG_A]); lua_setfield(l, -2, "a"); lua_pushinteger(l, e->regs[L6502_REG_X]); lua_setfield(l, -2, "x"); lua_pushinteger(l, e->regs[L6502_REG_Y]); lua_setfield(l, -2, "y"); + lua_pushinteger(l, e->regs[L6502_REG_FLAGS]); lua_setfield(l, -2, "flags"); lua_setfield(l, -2, "regs"); lua_newtable(l); lua_pushinteger(l, l6502_flag_get(e, L6502_FLAG_CARRY)); lua_setfield(l, -2, "carry"); @@ -107,7 +108,8 @@ int emu_write(lua_State *l) { int emu_emulate(lua_State *l); int emu_emulate(lua_State *l) { l6502_emu *e = get_emu(l); - l6502_emulate(e); + const char *ins = l6502_emulate(e); + lua_pushstring(l, ins); return 1; } -- cgit v1.3.1