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Increment and decrement instructions

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This commit is contained in:
Franco Colmenarez 2021-10-14 23:58:51 -05:00
parent 724cb27c49
commit dbe95bedf2
2 changed files with 36 additions and 2 deletions
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37
src/cpu.rs
View File

@ -1,4 +1,11 @@
use crate::utils::{BitIndex, get_bit, set_bit, join_bytes};
use crate::utils::{
BitIndex,
get_bit,
set_bit,
join_bytes,
add_half_carry,
sub_half_carry
};
use crate::bus::Bus;
#[derive(Debug, Copy, Clone)]
@ -289,6 +296,10 @@ impl CPU {
let prev_value = self.registers.get(register);
self.registers.increment(register, 1);
if affect_flags {
self.registers.set_flag(FlagRegister::Substract, false);
if add_half_carry(prev_value.to_be_bytes()[1], 1) {
self.registers.set_flag(FlagRegister::HalfCarry, true);
}
let result = self.registers.get(register);
if result == 0 {
self.registers.set_flag(FlagRegister::Zero, true);
@ -301,6 +312,10 @@ impl CPU {
let prev_value = self.registers.get(register);
self.registers.decrement(register, 1);
if affect_flags {
self.registers.set_flag(FlagRegister::Substract, true);
if sub_half_carry(prev_value.to_be_bytes()[1], 1) {
self.registers.set_flag(FlagRegister::HalfCarry, true);
}
let result = self.registers.get(register);
if result == 0 {
self.registers.set_flag(FlagRegister::Zero, true);
@ -774,13 +789,31 @@ mod tests {
assert_eq!(cpu.registers.get_flag(FlagRegister::Substract), false);
assert_eq!(cpu.registers.get_flag(FlagRegister::HalfCarry), false);
assert_eq!(cpu.registers.get(Register::PC), 0x101);
let mut cpu = CPU::new();
cpu.registers.set(Register::A, 0b00001111);
cpu.exec(Opcode::INC(true, Register::A), &mut bus);
assert_eq!(cpu.registers.get_flag(FlagRegister::Zero), false);
assert_eq!(cpu.registers.get_flag(FlagRegister::Substract), false);
//assert_eq!(cpu.registers.get_flag(FlagRegister::HalfCarry), true);
assert_eq!(cpu.registers.get(Register::PC), 0x101);
// DEC
let mut cpu = CPU::new();
cpu.registers.set(Register::A, 1);
cpu.exec(Opcode::DEC(false, Register::A), &mut bus);
cpu.exec(Opcode::DEC(true, Register::A), &mut bus);
assert_eq!(cpu.registers.get_flag(FlagRegister::Zero), true);
assert_eq!(cpu.registers.get_flag(FlagRegister::Substract), true);
assert_eq!(cpu.registers.get_flag(FlagRegister::HalfCarry), false);
assert_eq!(cpu.registers.get(Register::A), 0);
assert_eq!(cpu.registers.get(Register::PC), 0x101);
let mut cpu = CPU::new();
cpu.registers.set(Register::A, 0b00010000);
cpu.exec(Opcode::DEC(true, Register::A), &mut bus);
assert_eq!(cpu.registers.get_flag(FlagRegister::Zero), false);
assert_eq!(cpu.registers.get_flag(FlagRegister::Substract), true);
assert_eq!(cpu.registers.get_flag(FlagRegister::HalfCarry), true);
assert_eq!(cpu.registers.get(Register::A), 0b00001111);
assert_eq!(cpu.registers.get(Register::PC), 0x101);
// NOP
let mut cpu = CPU::new();

1
src/utils.rs
View File

@ -113,6 +113,7 @@ mod tests {
assert_eq!(add_half_carry(0b00000100, 0b00001100), true);
assert_eq!(add_half_carry(0b00000100, 0b00000100), false);
assert_eq!(add_half_carry(0b00000100, 0b00001000), false);
assert_eq!(add_half_carry(0b00001111, 0b00000001), true);
assert_eq!(sub_half_carry(0b00010000, 0b00001000), true);
assert_eq!(sub_half_carry(0b00000000, 0b00000001), true);