| 1 | use crate::instructions::Instruction; |
| 2 | use crate::memory::Memory; |
| 3 | |
| 4 | #[derive(Default, Debug)] |
| 5 | #[allow(dead_code)] |
| 6 | pub struct CPU { |
| 7 | pub a: u8, |
| 8 | pub b: u8, |
| 9 | pub c: u8, |
| 10 | pub d: u8, |
| 11 | |
| 12 | pub pc: u16, |
| 13 | pub sp: u16, |
| 14 | |
| 15 | pub zero: bool, |
| 16 | pub carry: bool, |
| 17 | |
| 18 | pub halted: bool, |
| 19 | } |
| 20 | |
| 21 | impl CPU { |
| 22 | pub fn debug_instr(&self, mem: &Memory) { |
| 23 | let opcode = mem.read(self.pc); |
| 24 | |
| 25 | println!( |
| 26 | "PC={:04X} {:<3} | A={:02X} B={:02X} C={:02X} D={:02X} | Z={} C={}", |
| 27 | self.pc, |
| 28 | Instruction::opcode_name(opcode), |
| 29 | self.a, |
| 30 | self.b, |
| 31 | self.c, |
| 32 | self.d, |
| 33 | self.zero as u8, |
| 34 | self.carry as u8 |
| 35 | ); |
| 36 | } |
| 37 | |
| 38 | pub fn step(&mut self, mem: &mut Memory) { |
| 39 | let opcode = mem.read(self.pc); |
| 40 | self.inc_pc(); |
| 41 | |
| 42 | match opcode { |
| 43 | x if x == Instruction::MOV_RI as u8 => self.mov_ri(mem), |
| 44 | x if x == Instruction::MOV_RR as u8 => self.mov_rr(mem), |
| 45 | x if x == Instruction::ADD as u8 => self.add(mem), |
| 46 | x if x == Instruction::SUB as u8 => self.sub(mem), |
| 47 | x if x == Instruction::JMP as u8 => self.jmp(mem), |
| 48 | x if x == Instruction::JZ as u8 => self.jz(mem), |
| 49 | x if x == Instruction::JNZ as u8 => self.jnz(mem), |
| 50 | x if x == Instruction::CMP_RI as u8 => self.cmp_ri(mem), |
| 51 | x if x == Instruction::CMP_RR as u8 => self.cmp_rr(mem), |
| 52 | x if x == Instruction::HLT as u8 => self.halt(), |
| 53 | _ => panic!("Unknown opcode {:02X}", opcode), |
| 54 | } |
| 55 | } |
| 56 | |
| 57 | pub fn inc_pc(&mut self) { |
| 58 | self.pc += 1; |
| 59 | } |
| 60 | |
| 61 | pub fn halt(&mut self) { |
| 62 | self.halted = true; |
| 63 | } |
| 64 | |
| 65 | pub fn mov_ri(&mut self, mem: &Memory) { |
| 66 | let reg = mem.read(self.pc); |
| 67 | self.inc_pc(); |
| 68 | let val = mem.read(self.pc); |
| 69 | self.inc_pc(); |
| 70 | |
| 71 | match reg { |
| 72 | 0 => self.a = val, |
| 73 | 1 => self.b = val, |
| 74 | 2 => self.c = val, |
| 75 | 3 => self.d = val, |
| 76 | _ => {} |
| 77 | } |
| 78 | |
| 79 | self.zero = val == 0; |
| 80 | } |
| 81 | |
| 82 | pub fn mov_rr(&mut self, mem: &Memory) { |
| 83 | let dest = mem.read(self.pc); |
| 84 | self.inc_pc(); |
| 85 | let src= mem.read(self.pc); |
| 86 | self.inc_pc(); |
| 87 | |
| 88 | let val = self.get_reg(src); |
| 89 | self.set_reg(dest, val); |
| 90 | |
| 91 | self.zero = val == 0; |
| 92 | } |
| 93 | |
| 94 | |
| 95 | pub fn add(&mut self, mem: &Memory) { |
| 96 | let dest = mem.read(self.pc); |
| 97 | self.pc += 1; |
| 98 | let src = mem.read(self.pc); |
| 99 | self.pc += 1; |
| 100 | |
| 101 | let (result, carry) = match (dest, src) { |
| 102 | (0, 0) => self.a.overflowing_add(self.a), |
| 103 | (0, 1) => self.a.overflowing_add(self.b), |
| 104 | (0, 2) => self.a.overflowing_add(self.c), |
| 105 | (0, 3) => self.a.overflowing_add(self.d), |
| 106 | |
| 107 | (1, 0) => self.b.overflowing_add(self.a), |
| 108 | (1, 1) => self.b.overflowing_add(self.b), |
| 109 | (1, 2) => self.b.overflowing_add(self.c), |
| 110 | (1, 3) => self.b.overflowing_add(self.d), |
| 111 | |
| 112 | (2, 0) => self.c.overflowing_add(self.a), |
| 113 | (2, 1) => self.c.overflowing_add(self.b), |
| 114 | (2, 2) => self.c.overflowing_add(self.c), |
| 115 | (2, 3) => self.c.overflowing_add(self.d), |
| 116 | |
| 117 | (3, 0) => self.d.overflowing_add(self.a), |
| 118 | (3, 1) => self.d.overflowing_add(self.b), |
| 119 | (3, 2) => self.d.overflowing_add(self.c), |
| 120 | (3, 3) => self.d.overflowing_add(self.d), |
| 121 | |
| 122 | _ => (0, false), |
| 123 | }; |
| 124 | |
| 125 | match dest { |
| 126 | 0 => self.a = result, |
| 127 | 1 => self.b = result, |
| 128 | 2 => self.c = result, |
| 129 | 3 => self.d = result, |
| 130 | _ => {} |
| 131 | } |
| 132 | |
| 133 | self.zero = result == 0; |
| 134 | self.carry = carry; |
| 135 | } |
| 136 | |
| 137 | pub fn sub(&mut self, mem: &Memory) { |
| 138 | let dest = mem.read(self.pc); |
| 139 | self.pc += 1; |
| 140 | let src = mem.read(self.pc); |
| 141 | self.pc += 1; |
| 142 | |
| 143 | let (result, borrow) = match (dest, src) { |
| 144 | (0, 0) => self.a.overflowing_sub(self.a), |
| 145 | (0, 1) => self.a.overflowing_sub(self.b), |
| 146 | (0, 2) => self.a.overflowing_sub(self.c), |
| 147 | (0, 3) => self.a.overflowing_sub(self.d), |
| 148 | |
| 149 | (1, 0) => self.b.overflowing_sub(self.a), |
| 150 | (1, 1) => self.b.overflowing_sub(self.b), |
| 151 | (1, 2) => self.b.overflowing_sub(self.c), |
| 152 | (1, 3) => self.b.overflowing_sub(self.d), |
| 153 | |
| 154 | (2, 0) => self.c.overflowing_sub(self.a), |
| 155 | (2, 1) => self.c.overflowing_sub(self.b), |
| 156 | (2, 2) => self.c.overflowing_sub(self.c), |
| 157 | (2, 3) => self.c.overflowing_sub(self.d), |
| 158 | |
| 159 | (3, 0) => self.d.overflowing_sub(self.a), |
| 160 | (3, 1) => self.d.overflowing_sub(self.b), |
| 161 | (3, 2) => self.d.overflowing_sub(self.c), |
| 162 | (3, 3) => self.d.overflowing_sub(self.d), |
| 163 | |
| 164 | _ => (0, false), |
| 165 | }; |
| 166 | |
| 167 | match dest { |
| 168 | 0 => self.a = result, |
| 169 | 1 => self.b = result, |
| 170 | 2 => self.c = result, |
| 171 | 3 => self.d = result, |
| 172 | _ => {} |
| 173 | } |
| 174 | |
| 175 | self.zero = result == 0; |
| 176 | self.carry = borrow; |
| 177 | } |
| 178 | |
| 179 | pub fn jmp(&mut self, mem: &Memory) { |
| 180 | let low = mem.read(self.pc) as u16; |
| 181 | self.inc_pc(); |
| 182 | let high = mem.read(self.pc) as u16; |
| 183 | self.inc_pc(); |
| 184 | |
| 185 | let addrs = (high << 8) | low; |
| 186 | |
| 187 | self.pc = addrs; |
| 188 | } |
| 189 | |
| 190 | pub fn jz(&mut self, mem: &Memory) { |
| 191 | let low = mem.read(self.pc) as u16; |
| 192 | self.inc_pc(); |
| 193 | let high = mem.read(self.pc) as u16; |
| 194 | self.inc_pc(); |
| 195 | |
| 196 | let addrs = (high << 8) | low; |
| 197 | |
| 198 | if self.zero { |
| 199 | self.pc = addrs; |
| 200 | } |
| 201 | } |
| 202 | |
| 203 | pub fn jnz(&mut self, mem: &Memory) { |
| 204 | let low = mem.read(self.pc) as u16; |
| 205 | self.inc_pc(); |
| 206 | let high = mem.read(self.pc) as u16; |
| 207 | self.inc_pc(); |
| 208 | |
| 209 | let addrs = (high << 8) | low; |
| 210 | |
| 211 | if !self.zero { |
| 212 | self.pc = addrs; |
| 213 | } |
| 214 | } |
| 215 | |
| 216 | pub fn cmp_rr(&mut self, mem: &Memory) { |
| 217 | let r1 = mem.read(self.pc); |
| 218 | self.inc_pc(); |
| 219 | let r2 = mem.read(self.pc); |
| 220 | self.inc_pc(); |
| 221 | |
| 222 | let v1 = self.get_reg(r1); |
| 223 | let v2 = self.get_reg(r2); |
| 224 | |
| 225 | let (result, borrow) = v1.overflowing_sub(v2); |
| 226 | |
| 227 | self.zero = result == 0; |
| 228 | self.carry = borrow; |
| 229 | } |
| 230 | |
| 231 | pub fn cmp_ri(&mut self, mem: &Memory) { |
| 232 | let r1 = mem.read(self.pc); |
| 233 | self.inc_pc(); |
| 234 | let r2 = mem.read(self.pc); |
| 235 | self.inc_pc(); |
| 236 | |
| 237 | let v1 = self.get_reg(r1); |
| 238 | |
| 239 | let (result, borrow) = v1.overflowing_sub(r2); |
| 240 | |
| 241 | self.zero = result == 0; |
| 242 | self.carry = borrow; |
| 243 | } |
| 244 | |
| 245 | |
| 246 | fn get_reg(&self, r: u8) -> u8 { |
| 247 | match r { |
| 248 | 0 => self.a, |
| 249 | 1 => self.b, |
| 250 | 2 => self.c, |
| 251 | 3 => self.d, |
| 252 | _ => 0, |
| 253 | } |
| 254 | } |
| 255 | |
| 256 | fn set_reg(&mut self, dest: u8, val: u8) { |
| 257 | match dest { |
| 258 | 0 => self.a = val, |
| 259 | 1 => self.b = val, |
| 260 | 2 => self.c = val, |
| 261 | 3 => self.d = val, |
| 262 | _ => {}, |
| 263 | } |
| 264 | } |
| 265 | |
| 266 | } |