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Implement LSR, INC, INX, INY

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This commit is contained in:
Johannes Muenzel 2014-11-02 15:40:34 -05:00
parent fe9610e3d8
commit b7e4125fcd
2 changed files with 104 additions and 14 deletions
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114
src/machine.rs
View File

@ -138,6 +138,22 @@ impl Machine {
self.dec_x();
}
(instruction::INC, instruction::UseAddress(addr)) => {
let m = self.memory.get_byte(addr);
let m = m + 1;
self.memory.set_byte(addr, m);
let i = m as i8;
Machine::set_flags_from_i8(&mut self.registers.status, i);
}
(instruction::INX, instruction::UseImplied) => {
let x = self.registers.index_x + 1;
self.load_x_register(x);
}
(instruction::INY, instruction::UseImplied) => {
let y = self.registers.index_y + 1;
self.load_y_register(y);
}
(instruction::JMP, instruction::UseAddress(addr)) => {
self.jump(addr)
}
@ -172,6 +188,19 @@ impl Machine {
self.load_y_register(val as i8);
}
(instruction::LSR, instruction::UseImplied) => {
// Accumulator mode
let mut val = self.registers.accumulator as u8;
Machine::shift_right_with_flags(&mut val,
&mut self.registers.status);
self.registers.accumulator = val as i8;
}
(instruction::LSR, instruction::UseAddress(addr)) => {
Machine::shift_right_with_flags(
self.memory.get_byte_mut_ref(addr),
&mut self.registers.status);
}
(instruction::SBC, instruction::UseImmediate(val)) => {
debug!("subtract with carry immediate: {}", val);
self.subtract_with_carry(val as i8);
@ -252,11 +281,7 @@ impl Machine {
}
}
fn load_register_with_flags(register: &mut i8,
status: &mut Status,
value: i8) {
*register = value;
fn set_flags_from_i8(status: &mut Status, value: i8) {
let is_zero = value == 0;
let is_negative = value < 0;
@ -267,22 +292,37 @@ impl Machine {
..StatusArgs::none() } ));
}
fn shift_right_with_flags(p_val: &mut u8, status: &mut Status) {
let bit0 = *p_val & 1;
*p_val = *p_val >> 1;
status.set_with_mask(
PS_CARRY,
Status::new(StatusArgs { carry: bit0 == 1,
..StatusArgs::none() } ));
Machine::set_flags_from_i8(status, *p_val as i8);
}
fn set_i8_with_flags(mem: &mut i8, status: &mut Status, value: i8) {
*mem = value;
Machine::set_flags_from_i8(status, value);
}
fn load_x_register(&mut self, value: i8) {
Machine::load_register_with_flags(&mut self.registers.index_x,
&mut self.registers.status,
value);
Machine::set_i8_with_flags(&mut self.registers.index_x,
&mut self.registers.status,
value);
}
fn load_y_register(&mut self, value: i8) {
Machine::load_register_with_flags(&mut self.registers.index_y,
&mut self.registers.status,
value);
Machine::set_i8_with_flags(&mut self.registers.index_y,
&mut self.registers.status,
value);
}
fn load_accumulator(&mut self, value: i8) {
Machine::load_register_with_flags(&mut self.registers.accumulator,
&mut self.registers.status,
value);
Machine::set_i8_with_flags(&mut self.registers.accumulator,
&mut self.registers.status,
value);
}
fn add_with_carry(&mut self, value: i8) {
@ -563,6 +603,52 @@ fn decrement_memory_test() {
assert_eq!(machine.registers.status.contains(PS_NEGATIVE), true);
}
#[test]
fn logical_shift_right_test() {
// Testing UseImplied version (which targets the accumulator) only, for now
let mut machine = Machine::new();
machine.execute_instruction((instruction::LDA,
instruction::UseImmediate(0)));
machine.execute_instruction((instruction::LSR,
instruction::UseImplied));
assert_eq!(machine.registers.accumulator, 0);
assert_eq!(machine.registers.status.contains(PS_CARRY), false);
assert_eq!(machine.registers.status.contains(PS_ZERO), true);
assert_eq!(machine.registers.status.contains(PS_NEGATIVE), false);
assert_eq!(machine.registers.status.contains(PS_OVERFLOW), false);
machine.execute_instruction((instruction::LDA,
instruction::UseImmediate(1)));
machine.execute_instruction((instruction::LSR,
instruction::UseImplied));
assert_eq!(machine.registers.accumulator, 0);
assert_eq!(machine.registers.status.contains(PS_CARRY), true);
assert_eq!(machine.registers.status.contains(PS_ZERO), true);
assert_eq!(machine.registers.status.contains(PS_NEGATIVE), false);
assert_eq!(machine.registers.status.contains(PS_OVERFLOW), false);
machine.execute_instruction((instruction::LDA,
instruction::UseImmediate(255)));
machine.execute_instruction((instruction::LSR,
instruction::UseImplied));
assert_eq!(machine.registers.accumulator, 0x7F);
assert_eq!(machine.registers.status.contains(PS_CARRY), true);
assert_eq!(machine.registers.status.contains(PS_ZERO), false);
assert_eq!(machine.registers.status.contains(PS_NEGATIVE), false);
assert_eq!(machine.registers.status.contains(PS_OVERFLOW), false);
machine.execute_instruction((instruction::LDA,
instruction::UseImmediate(254)));
machine.execute_instruction((instruction::LSR,
instruction::UseImplied));
assert_eq!(machine.registers.accumulator, 0x7F);
assert_eq!(machine.registers.status.contains(PS_CARRY), false);
assert_eq!(machine.registers.status.contains(PS_ZERO), false);
assert_eq!(machine.registers.status.contains(PS_NEGATIVE), false);
assert_eq!(machine.registers.status.contains(PS_OVERFLOW), false);
}
#[test]
fn dec_x_test() {
let mut machine = Machine::new();

4
src/memory.rs
View File

@ -61,6 +61,10 @@ impl Memory {
self.bytes[address.to_uint()]
}
pub fn get_byte_mut_ref(&mut self, address: Address) -> &mut u8 {
&mut self.bytes[address.to_uint()]
}
pub fn get_slice(&self, Address(start): Address,
AddressDiff(diff): AddressDiff) -> &[u8] {
let start = start as uint;