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implement RTI as well

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This commit is contained in:
Sam M W 2023-04-15 15:27:51 +01:00
parent 1b90243738
commit 18164c7abf
1 changed files with 12 additions and 0 deletions
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12
src/cpu.rs
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@ -445,6 +445,18 @@ impl<M: Bus> CPU<M> {
CPU::<M>::rotate_right_with_flags(&mut operand, &mut self.registers.status); CPU::<M>::rotate_right_with_flags(&mut operand, &mut self.registers.status);
self.memory.set_byte(addr, operand); self.memory.set_byte(addr, operand);
} }
(Instruction::RTI, OpInput::UseImplied) => {
// Pull status
self.pull_from_stack();
let val: u8 = self.pull_from_stack();
// The `truncate` here won't do anything because we have a
// constant for the single unused flags bit. This probably
// corresponds to the behavior of the 6502...? FIXME: verify
self.registers.status = Status::from_bits_truncate(val);
let pcl: u8 = self.pull_from_stack();
let pch: u8 = self.fetch_from_stack();
self.registers.program_counter = ((pch as u16) << 8) | pcl as u16;
}
(Instruction::RTS, OpInput::UseImplied) => { (Instruction::RTS, OpInput::UseImplied) => {
self.pull_from_stack(); self.pull_from_stack();
let pcl: u8 = self.pull_from_stack(); let pcl: u8 = self.pull_from_stack();