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Fix PUSH instruction

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This commit is contained in:
Franco Colmenarez 2021-10-16 20:50:31 -05:00
parent 989971af8b
commit 12b43ee985
1 changed files with 9 additions and 7 deletions
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16
src/cpu.rs
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@ -446,17 +446,19 @@ impl CPU {
Opcode::RST(address) => self.exec(Opcode::CALL(OpcodeParameter::U16(address as u16)), bus),
// PUSH onto the stack
Opcode::PUSH(register) => {
let val = self.registers.get(register).to_be_bytes();
let sp = self.registers.get(Register::SP);
bus.write(sp - 1, val[1]);
bus.write(sp - 2, val[0]);
self.registers.increment(Register::PC, 1);
self.registers.decrement(Register::SP, 2);
let val = self.registers.get(register).to_be_bytes();
self.registers.decrement(Register::SP, 1);
bus.write(self.registers.get(Register::SP), val[0]);
self.registers.decrement(Register::SP, 1);
bus.write(self.registers.get(Register::SP), val[1]);
},
// POP onto the stack
Opcode::POP(register) => {
self.registers.increment(Register::PC, 1);
let sp = self.registers.get(Register::SP);
self.registers.set(register, bus.read_16bit(sp));
let val = bus.read_16bit(sp);
self.registers.set(register, val);
self.registers.increment(Register::SP, 2);
},
// RET, same as POP PC when no parameter is specified
@ -1012,7 +1014,7 @@ mod tests {
cpu.registers.set(Register::SP, addr);
cpu.registers.set(Register::AF, 0x1234);
cpu.exec(Opcode::PUSH(Register::AF), &mut bus);
assert_eq!(bus.read_16bit(addr - 2), 0x3412);
assert_eq!(bus.read_16bit(addr - 2), 0x1234);
assert_eq!(cpu.registers.get(Register::SP), addr - 2);
assert_eq!(cpu.registers.get(Register::PC), 0x101);