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-rw-r--r--src/mos6502.rs75
1 files changed, 36 insertions, 39 deletions
diff --git a/src/mos6502.rs b/src/mos6502.rs
index 58ac217..c439700 100644
--- a/src/mos6502.rs
+++ b/src/mos6502.rs
@@ -132,7 +132,7 @@ pub mod disasm {
format!("${:02x}, y", code.next().unwrap())
}
fn rel(code: T) -> String {
- let b = *code.next().unwrap() as i8;
+ let b = *code.next().unwrap() as i8 as i16;
if b >= 0 {
format!("+${:02x}, x", b)
} else {
@@ -229,10 +229,9 @@ mod ops {
let opr1 = cpu.a as u16;
let opr2 = match cpu.addr_mode {
AddrMode::Immediate => cpu.imm_val,
- AddrMode::Accumulator => cpu.a,
- AddrMode::EffAddr => cpu.mem.read(cpu.ea)
+ _ => cpu.mem.read(cpu.ea)
} as u16;
- let res = opr1 + opr2 + cpu.get_carry() as u16;
+ let res = opr1 + opr2 + (cpu.get_carry() as u16);
let mut status = cpu.status & !(CARRY_FLAG | ZERO_FLAG | OVER_FLAG | NEG_FLAG);
cpu.a = res as u8;
status |= (res > 0xff) as u8; /* carry flag */
@@ -248,10 +247,9 @@ mod ops {
let opr1 = cpu.a as u16;
let opr2 = match cpu.addr_mode {
AddrMode::Immediate => cpu.imm_val,
- AddrMode::Accumulator => cpu.a,
- AddrMode::EffAddr => cpu.mem.read(cpu.ea)
+ _ => cpu.mem.read(cpu.ea)
} as u16;
- let res = opr1 + (0xff - opr2) + cpu.get_carry() as u16;
+ let res = opr1 + (0xff - opr2) + (cpu.get_carry() as u16);
let mut status = cpu.status & !(CARRY_FLAG | ZERO_FLAG | OVER_FLAG | NEG_FLAG);
cpu.a = res as u8;
status |= (res > 0xff) as u8; /* carry flag */
@@ -269,9 +267,9 @@ mod ops {
AddrMode::Immediate => cpu.imm_val,
_ => cpu.mem.read(cpu.ea)
} as u16;
- let res = opr1 - opr2;
+ let res = opr1.wrapping_sub(opr2);
let mut status = cpu.status & !(CARRY_FLAG | ZERO_FLAG | NEG_FLAG);
- status |= (res < 0x100) as u8; /* carry flag */
+ status |= (res < 0x100) as u8; /* if opr1 >= opr2 */
check_zero!(status, res);
check_neg!(status, res);
cpu.status = status;
@@ -286,16 +284,16 @@ mod ops {
macro_rules! make_delta {
($f: ident, $d: expr) => (
fn $f(cpu: &mut CPU) {
- let res = cpu.mem.read(cpu.ea) as u16 + $d;
+ let res = cpu.mem.read(cpu.ea).wrapping_add($d);
let mut status = cpu.status & !(ZERO_FLAG | NEG_FLAG);
- cpu.mem.write(cpu.ea, res as u8);
+ cpu.mem.write(cpu.ea, res);
check_zero!(status, res);
check_neg!(status, res);
cpu.status = status;
});
($f: ident, $d: expr, $r: ident) => (
fn $f(cpu: &mut CPU) {
- let res = cpu.$r as u16 + $d;
+ let res = cpu.$r.wrapping_add($d);
let mut status = cpu.status & !(ZERO_FLAG | NEG_FLAG);
cpu.$r = res as u8;
check_zero!(status, res);
@@ -514,8 +512,11 @@ mod ops {
macro_rules! make_ld {
($f: ident, $r: ident) => (fn $f(cpu: &mut CPU) {
let mut status = cpu.status & !(ZERO_FLAG | NEG_FLAG);
- let res = cpu.mem.read(cpu.ea);
- cpu.a = res;
+ let res = match cpu.addr_mode {
+ AddrMode::Immediate => cpu.imm_val,
+ _ => cpu.mem.read(cpu.ea)
+ };
+ cpu.$r = res;
check_zero!(status, res);
check_neg!(status, res);
cpu.status = status;
@@ -612,20 +613,20 @@ mod addr {
fn zpx(cpu: &mut CPU) {
cpu.addr_mode = AddrMode::EffAddr;
cpu.ea = (cpu.mem.read(cpu.opr)
- .wrapping_add(cpu.x)) as u16;
+ .wrapping_add(cpu.x)) as u16;
}
fn zpy(cpu: &mut CPU) {
cpu.addr_mode = AddrMode::EffAddr;
cpu.ea = (cpu.mem.read(cpu.opr)
- .wrapping_add(cpu.y)) as u16;
+ .wrapping_add(cpu.y)) as u16;
}
fn rel(cpu: &mut CPU) {
cpu.addr_mode = AddrMode::EffAddr;
let base = cpu.pc;
let offset = cpu.mem.read(cpu.opr) as i8 as i16;
- let sum = (base & 0xff) + offset as u16;
+ let sum = ((base & 0xff) as i16 + offset) as u16;
cpu.ea = (base & 0xff00).wrapping_add(sum);
cpu.cycle += (sum >> 8) as u32;
}
@@ -638,7 +639,7 @@ mod addr {
fn abx(cpu: &mut CPU) {
cpu.addr_mode = AddrMode::EffAddr;
let base = read16!(cpu.mem, cpu.opr);
- let sum = (base & 0xff) + cpu.x as u16;
+ let sum = (base & 0xff) + (cpu.x as u16);
cpu.ea = (base & 0xff00).wrapping_add(sum);
cpu.cycle += (sum >> 8) as u32; /* boundary cross if carry */
}
@@ -646,7 +647,7 @@ mod addr {
fn aby(cpu: &mut CPU) {
cpu.addr_mode = AddrMode::EffAddr;
let base = read16!(cpu.mem, cpu.opr);
- let sum = (base & 0xff) + cpu.y as u16;
+ let sum = (base & 0xff) + (cpu.y as u16);
cpu.ea = (base & 0xff00).wrapping_add(sum);
cpu.cycle += (sum >> 8) as u32; /* boundary cross if carry */
}
@@ -659,17 +660,15 @@ mod addr {
fn xin(cpu: &mut CPU) {
cpu.addr_mode = AddrMode::EffAddr;
- let addr = cpu.mem.read(
- cpu.mem.read(cpu.opr)
- .wrapping_add(cpu.x) as u16) as u16;
- cpu.ea = read16!(cpu.mem, addr);
+ cpu.ea = read16!(cpu.mem,
+ cpu.mem.read(cpu.opr)
+ .wrapping_add(cpu.x) as u16) as u16;
}
fn iny(cpu: &mut CPU) {
cpu.addr_mode = AddrMode::EffAddr;
- let addr = cpu.mem.read(cpu.mem.read(cpu.opr) as u16) as u16;
- let base = read16!(cpu.mem, addr);
- let sum = (base & 0xff) + cpu.y as u16;
+ let base = read16!(cpu.mem, cpu.mem.read(cpu.opr) as u16);
+ let sum = (base & 0xff) + (cpu.y as u16);
cpu.ea = (base & 0xff00).wrapping_add(sum);
cpu.cycle += (sum >> 8) as u32; /* boundary cross if carry */
}
@@ -703,7 +702,7 @@ pub struct CPU<'a> {
imm_val: u8,
pub cycle: u32,
int: Option<IntType>,
- pub mem: &'a mut VMem
+ pub mem: &'a VMem
}
macro_rules! make_int {
@@ -728,7 +727,7 @@ impl<'a> CPU<'a> {
#[inline(always)] pub fn get_over(&self) -> u8 { (self.status >> 6) & 1 }
#[inline(always)] pub fn get_neg(&self) -> u8 { (self.status >> 7) & 1 }
- pub fn new(mem: &'a mut VMem) -> Self {
+ pub fn new(mem: &'a VMem) -> Self {
let pc = read16!(mem, RESET_VECTOR as u16);
/* nes power up state */
let a = 0;
@@ -750,14 +749,21 @@ impl<'a> CPU<'a> {
make_int!(irq, IRQ_VECTOR);
pub fn step(&mut self) {
- let pc = self.pc;
match self.int {
Some(IntType::NMI) => self.nmi(),
Some(IntType::IRQ) => self.irq(),
_ => ()
}
self.int = None;
+ let pc = self.pc;
let opcode = self.mem.read(pc) as usize;
+ let len = INST_LENGTH[opcode];
+ let mut code = vec![0; len as usize];
+ for i in 0..len as u16 {
+ code[i as usize] = self.mem.read(pc + i);
+ }
+ println!("0x{:04x} {} a:{} x:{} y:{}",
+ pc, disasm::parse(opcode as u8, &code[1..]), self.a, self.x, self.y);
/* update opr pointing to operands of current inst */
self.opr = pc.wrapping_add(1);
/* update program counter pointing to next inst */
@@ -769,16 +775,7 @@ impl<'a> CPU<'a> {
self.cycle += INST_CYCLE[opcode] as u32;
}
- pub fn powerup(&mut self) {
- self.pc = read16!(self.mem, RESET_VECTOR as u16);
- /* nes power up state */
- self.a = 0;
- self.x = 0;
- self.y = 0;
- self.sp = 0xfd;
- self.status = 0x34;
- self.cycle = 0;
- }
+ pub fn get_pc(&self) -> u16 { self.pc }
pub fn reset(&mut self) {
self.pc = read16!(self.mem, RESET_VECTOR as u16);
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