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SBC opcodes

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This commit is contained in:
Franco Colmenarez
2022-11-20 12:10:17 -05:00
parent f8a6872b8c
commit 4ddc3b3aa7
2 changed files with 69 additions and 22 deletions
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snes-core/src/cpu/instructions.rs
+55 -8
View File
@@ -38,7 +38,7 @@ impl CPU {
true => alu::adc8bcd(target as u8, value, carry_flag),
false => alu::adc8bin(target as u8, value, carry_flag),
};
self.registers.a = (self.registers.a & 0x00FF) | (result as u16);
self.registers.a = (self.registers.a & 0xFF00) | (result as u16);
self.registers.set_carry_flag(is_carry);
self.registers.set_negative_flag(is_negative);
self.registers.set_zero_flag(is_zero);
@@ -57,6 +57,39 @@ impl CPU {
};
}
fn sbc(&mut self, bus: &Bus, addressing_mode: AddressingMode) {
// if the M flag is set, perform 8 bit addition.
// Otherwise, 16 bit addition
let carry_flag = self.registers.get_carry_flag();
let is_decimal_mode = self.registers.get_decimal_mode_flag();
let is_8bit = self.registers.get_memory_select_flag();
let target = self.registers.a;
match is_8bit {
true => {
let value = self.get_8bit_from_address(bus, addressing_mode);
let (result, is_carry, is_negative, is_zero) = match is_decimal_mode {
true => alu::sbc8bcd(target as u8, value, carry_flag),
false => alu::sbc8bin(target as u8, value, carry_flag),
};
self.registers.a = (self.registers.a & 0xFF00) | (result as u16);
self.registers.set_carry_flag(is_carry);
self.registers.set_negative_flag(is_negative);
self.registers.set_zero_flag(is_zero);
},
false => {
let value = self.get_16bit_from_address(bus, addressing_mode);
let (result, is_carry, is_negative, is_zero) = match is_decimal_mode {
true => alu::sbc16bcd(target, value, carry_flag),
false => alu::sbc16bin(target, value, carry_flag),
};
self.registers.a = result;
self.registers.set_carry_flag(is_carry);
self.registers.set_negative_flag(is_negative);
self.registers.set_zero_flag(is_zero);
}
};
}
pub fn execute_opcode(&mut self, opcode: u8, bus: &Bus) {
type A = AddressingMode;
type I = IndexRegister;
@@ -77,6 +110,22 @@ impl CPU {
0x77 => self.adc(bus, A::DirectPageIndirectLongIndexed(I::Y)),
0x63 => self.adc(bus, A::StackRelative),
0x73 => self.adc(bus, A::StackRelativeIndirectIndexed(I::Y)),
// SBC
0xE9 => self.sbc(bus, A::Immediate),
0xED => self.sbc(bus, A::Absolute),
0xEF => self.sbc(bus, A::AbsoluteLong),
0xE5 => self.sbc(bus, A::DirectPage),
0xF2 => self.sbc(bus, A::DirectPageIndirect),
0xE7 => self.sbc(bus, A::DirectPageIndirectLong),
0xFD => self.sbc(bus, A::AbsoluteIndexed(I::X)),
0xFF => self.sbc(bus, A::AbsoluteLongIndexed(I::X)),
0xF9 => self.sbc(bus, A::AbsoluteIndexed(I::Y)),
0xF5 => self.sbc(bus, A::DirectPageIndexed(I::X)),
0xE1 => self.sbc(bus, A::DirectPageIndexedIndirect(I::X)),
0xF1 => self.sbc(bus, A::DirectPageIndirectIndexed(I::Y)),
0xF7 => self.sbc(bus, A::DirectPageIndirectLongIndexed(I::Y)),
0xE3 => self.sbc(bus, A::StackRelative),
0xF3 => self.sbc(bus, A::StackRelativeIndirectIndexed(I::Y)),
_ => println!("Invalid opcode: {:02X}", opcode),
}
}
@@ -101,19 +150,17 @@ mod cpu_instructions_tests {
}
#[test]
fn test_dec() {
/*
fn test_sbc() {
let mut cpu = CPU::new();
let mut bus = Bus::new();
cpu.registers.a = 0x0000;
cpu.registers.a = 0x0001;
cpu.registers.pbr = 0x00;
cpu.registers.pc = 0x0000;
cpu.registers.set_memory_select_flag(true);
bus.write(0x000001, 1);
// cpu.dec(&bus, AddressingMode::Immediate);
assert_eq!(cpu.registers.a, 1);
cpu.sbc(&bus, AddressingMode::Immediate);
assert_eq!(cpu.registers.a, 0);
assert!(!cpu.registers.get_carry_flag());
assert!(!cpu.registers.get_zero_flag());
*/
assert!(cpu.registers.get_zero_flag());
}
}
snes-core/src/utils/alu.rs
+14 -14
View File
@@ -68,7 +68,7 @@ pub fn adc16bcd(target: u16, value: u16, carry: bool) -> (u16, bool, bool, bool)
(result, is_carry, is_negative, is_zero)
}
pub fn dec8bin(target: u8, value: u8, carry: bool) -> (u8, bool, bool, bool) {
pub fn sbc8bin(target: u8, value: u8, carry: bool) -> (u8, bool, bool, bool) {
let is_carry = match target.checked_sub(value) {
None => true,
Some(res) => match res.checked_sub(carry as u8) {
@@ -84,7 +84,7 @@ pub fn dec8bin(target: u8, value: u8, carry: bool) -> (u8, bool, bool, bool) {
(result, is_carry, is_negative, is_zero)
}
pub fn dec16bin(target: u16, value: u16, carry: bool) -> (u16, bool, bool, bool) {
pub fn sbc16bin(target: u16, value: u16, carry: bool) -> (u16, bool, bool, bool) {
let is_carry = match target.checked_sub(value) {
None => true,
Some(res) => match res.checked_sub(carry as u16) {
@@ -100,7 +100,7 @@ pub fn dec16bin(target: u16, value: u16, carry: bool) -> (u16, bool, bool, bool)
(result, is_carry, is_negative, is_zero)
}
pub fn dec8bcd(target: u8, value: u8, carry: bool) -> (u8, bool, bool, bool) {
pub fn sbc8bcd(target: u8, value: u8, carry: bool) -> (u8, bool, bool, bool) {
let mut is_carry = carry;
let target = target as u16;
let value = !(value as u16);
@@ -120,7 +120,7 @@ pub fn dec8bcd(target: u8, value: u8, carry: bool) -> (u8, bool, bool, bool) {
(result, is_carry, is_negative, is_zero)
}
pub fn dec16bcd(target: u16, value: u16, carry: bool) -> (u16, bool, bool, bool) {
pub fn sbc16bcd(target: u16, value: u16, carry: bool) -> (u16, bool, bool, bool) {
let mut is_carry = carry;
let target = target as u32;
let value = !(value as u32);
@@ -307,19 +307,19 @@ mod alu_tests {
#[test]
fn test_dec8bin() {
let (result, carry, negative, zero) = dec8bin(1, 1, false);
let (result, carry, negative, zero) = sbc8bin(1, 1, false);
assert_eq!(result, 0);
assert_eq!(carry, false);
assert_eq!(negative, false);
assert_eq!(zero, true);
let (result, carry, negative, zero) = dec8bin(0, 1, false);
let (result, carry, negative, zero) = sbc8bin(0, 1, false);
assert_eq!(result, 0b11111111);
assert_eq!(carry, true);
assert_eq!(negative, true);
assert_eq!(zero, false);
let (result, carry, negative, zero) = dec8bin(0, 1, true);
let (result, carry, negative, zero) = sbc8bin(0, 1, true);
assert_eq!(result, 0b11111110);
assert_eq!(carry, true);
assert_eq!(negative, true);
@@ -328,19 +328,19 @@ mod alu_tests {
#[test]
fn test_dec16bin() {
let (result, carry, negative, zero) = dec16bin(1, 1, false);
let (result, carry, negative, zero) = sbc16bin(1, 1, false);
assert_eq!(result, 0);
assert_eq!(carry, false);
assert_eq!(negative, false);
assert_eq!(zero, true);
let (result, carry, negative, zero) = dec16bin(0, 1, false);
let (result, carry, negative, zero) = sbc16bin(0, 1, false);
assert_eq!(result, 0b11111111_11111111);
assert_eq!(carry, true);
assert_eq!(negative, true);
assert_eq!(zero, false);
let (result, carry, negative, zero) = dec16bin(0, 1, true);
let (result, carry, negative, zero) = sbc16bin(0, 1, true);
assert_eq!(result, 0b11111111_11111110);
assert_eq!(carry, true);
assert_eq!(negative, true);
@@ -349,13 +349,13 @@ mod alu_tests {
#[test]
fn test_dec8bcd() {
let (result, carry, negative, zero) = dec8bcd(0x49, 0x48, false);
let (result, carry, negative, zero) = sbc8bcd(0x49, 0x48, false);
assert_eq!(result, 0x00);
assert_eq!(carry, true);
assert_eq!(negative, false);
assert_eq!(zero, true);
let (result, carry, negative, zero) = dec8bcd(0x49, 0x50, true);
let (result, carry, negative, zero) = sbc8bcd(0x49, 0x50, true);
assert_eq!(result, 0x99);
assert_eq!(carry, false);
assert_eq!(negative, true);
@@ -364,13 +364,13 @@ mod alu_tests {
#[test]
fn test_dec16bcd() {
let (result, carry, negative, zero) = dec16bcd(0x4999, 0x4998, false);
let (result, carry, negative, zero) = sbc16bcd(0x4999, 0x4998, false);
assert_eq!(result, 0x0000);
assert_eq!(carry, true);
assert_eq!(negative, false);
assert_eq!(zero, true);
let (result, carry, negative, zero) = dec16bcd(0x4999, 0x5000, true);
let (result, carry, negative, zero) = sbc16bcd(0x4999, 0x5000, true);
assert_eq!(result, 0x9999);
assert_eq!(carry, false);
assert_eq!(negative, true);