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Added ABCD, SBCD, and TAS instructions to m68k

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This commit is contained in:
transistor 2021-12-03 15:32:17 -08:00
parent d33a3c160b
commit 75e4a760eb
2 changed files with 37 additions and 8 deletions
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4
src/cpus/m68k/decode.rs
View File

@ -405,7 +405,7 @@ impl M68kDecoder {
let regx = get_high_reg(ins);
let regy = get_low_reg(ins);
match (ins & 0x08) == 0 {
match (ins & 0x08) != 0 {
false => Ok(Instruction::SBCD(Target::DirectDReg(regy), Target::DirectDReg(regx))),
true => Ok(Instruction::SBCD(Target::IndirectARegDec(regy), Target::IndirectARegDec(regx))),
}
@ -477,7 +477,7 @@ impl M68kDecoder {
let regx = get_high_reg(ins);
let regy = get_low_reg(ins);
match (ins & 0x08) == 0 {
match (ins & 0x08) != 0 {
false => Ok(Instruction::ABCD(Target::DirectDReg(regy), Target::DirectDReg(regx))),
true => Ok(Instruction::ABCD(Target::IndirectARegDec(regy), Target::IndirectARegDec(regx))),
}

41
src/cpus/m68k/execute.rs
View File

@ -167,8 +167,16 @@ impl M68k {
pub fn execute_current(&mut self) -> Result<(), Error> {
self.timer.execute.start();
match self.decoder.instruction {
//Instruction::ABCD(Target) => {
//},
Instruction::ABCD(src, dest) => {
let value = convert_from_bcd(self.get_target_value(src, Size::Byte)? as u8);
let existing = convert_from_bcd(self.get_target_value(dest, Size::Byte)? as u8);
let result = existing.wrapping_add(value).wrapping_add(self.get_flag(Flags::Extend) as u8);
let carry = result > 99;
self.set_target_value(dest, convert_to_bcd(result) as u32, Size::Byte)?;
self.set_flag(Flags::Zero, result == 0);
self.set_flag(Flags::Carry, carry);
self.set_flag(Flags::Extend, carry);
},
Instruction::ADD(src, dest, size) => {
let value = self.get_target_value(src, size)?;
let existing = self.get_target_value(dest, size)?;
@ -681,8 +689,16 @@ impl M68k {
self.state.sr = flags;
self.state.status = Status::Stopped;
},
//Instruction::SBCD(Target) => {
//},
Instruction::SBCD(src, dest) => {
let value = convert_from_bcd(self.get_target_value(src, Size::Byte)? as u8);
let existing = convert_from_bcd(self.get_target_value(dest, Size::Byte)? as u8);
let result = existing.wrapping_sub(value).wrapping_sub(self.get_flag(Flags::Extend) as u8);
let borrow = existing < value;
self.set_target_value(dest, convert_to_bcd(result) as u32, Size::Byte)?;
self.set_flag(Flags::Zero, result == 0);
self.set_flag(Flags::Carry, borrow);
self.set_flag(Flags::Extend, borrow);
},
Instruction::SUB(src, dest, size) => {
let value = self.get_target_value(src, size)?;
let existing = self.get_target_value(dest, size)?;
@ -713,8 +729,14 @@ impl M68k {
let value = self.state.d_reg[reg as usize];
self.state.d_reg[reg as usize] = ((value & 0x0000FFFF) << 16) | ((value & 0xFFFF0000) >> 16);
},
//Instruction::TAS(Target) => {
//},
Instruction::TAS(target) => {
let value = self.get_target_value(target, Size::Byte)?;
self.set_flag(Flags::Negative, (value & 0x80) != 0);
self.set_flag(Flags::Zero, value == 0);
self.set_flag(Flags::Overflow, false);
self.set_flag(Flags::Carry, false);
self.set_target_value(target, value | 0x80, Size::Byte)?;
},
Instruction::TST(target, size) => {
let value = self.get_target_value(target, size)?;
self.set_logic_flags(value, size);
@ -1255,6 +1277,13 @@ fn rotate_operation(value: u32, size: Size, dir: ShiftDirection, use_extend: Opt
}
}
fn convert_from_bcd(value: u8) -> u8 {
(value >> 4) * 10 + (value & 0x0F)
}
fn convert_to_bcd(value: u8) -> u8 {
(((value / 10) & 0x0F) << 4) | ((value % 10) & 0x0F)
}
fn get_value_sized(value: u32, size: Size) -> u32 {
match size {