| 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 | fn push16(&mut self, mem: &mut Memory, val: u16) { |
| 23 | self.dec_sp(); |
| 24 | mem.write(self.sp, (val >> 8) as u8); // high |
| 25 | self.dec_sp(); |
| 26 | mem.write(self.sp, (val & 0xFF) as u8); // low |
| 27 | } |
| 28 | |
| 29 | fn pop16(&mut self, mem: &mut Memory) -> u16 { |
| 30 | let low = mem.read(self.sp) as u16; |
| 31 | self.inc_sp(); |
| 32 | let high = mem.read(self.sp) as u16; |
| 33 | self.inc_sp(); |
| 34 | |
| 35 | (high << 8) | low |
| 36 | } |
| 37 | |
| 38 | pub fn debug_instr(&self, mem: &Memory) { |
| 39 | let opcode = mem.read(self.pc); |
| 40 | |
| 41 | println!( |
| 42 | "PC={:04X} {:<3} | A={:02X} B={:02X} C={:02X} D={:02X} | Z={} C={}", |
| 43 | self.pc, |
| 44 | Instruction::opcode_name(opcode), |
| 45 | self.a, |
| 46 | self.b, |
| 47 | self.c, |
| 48 | self.d, |
| 49 | self.zero as u8, |
| 50 | self.carry as u8 |
| 51 | ); |
| 52 | } |
| 53 | |
| 54 | pub fn step(&mut self, mem: &mut Memory) { |
| 55 | let opcode = mem.read(self.pc); |
| 56 | self.inc_pc(); |
| 57 | |
| 58 | match opcode { |
| 59 | x if x == Instruction::MOV_RI as u8 => self.mov_ri(mem), |
| 60 | x if x == Instruction::MOV_RR as u8 => self.mov_rr(mem), |
| 61 | x if x == Instruction::ADD_RR as u8 => self.add_rr(mem), |
| 62 | x if x == Instruction::ADD_RI as u8 => self.add_ri(mem), |
| 63 | x if x == Instruction::SUB_RR as u8 => self.sub_rr(mem), |
| 64 | x if x == Instruction::SUB_RI as u8 => self.sub_ri(mem), |
| 65 | x if x == Instruction::JMP as u8 => self.jmp(mem), |
| 66 | x if x == Instruction::JZ as u8 => self.jz(mem), |
| 67 | x if x == Instruction::JNZ as u8 => self.jnz(mem), |
| 68 | x if x == Instruction::CMP_RI as u8 => self.cmp_ri(mem), |
| 69 | x if x == Instruction::CMP_RR as u8 => self.cmp_rr(mem), |
| 70 | x if x == Instruction::MUL as u8 => self.mul(mem), |
| 71 | x if x == Instruction::DIV as u8 => self.div(mem), |
| 72 | x if x == Instruction::CALL as u8 => self.call(mem), |
| 73 | x if x == Instruction::RET as u8 => self.ret(mem), |
| 74 | x if x == Instruction::SYS as u8 => self.syscall(mem), |
| 75 | x if x == Instruction::HLT as u8 => self.halt(), |
| 76 | _ => panic!("Unknown opcode {:02X}", opcode), |
| 77 | } |
| 78 | } |
| 79 | |
| 80 | pub fn inc_pc(&mut self) { |
| 81 | self.pc += 1; |
| 82 | } |
| 83 | |
| 84 | pub fn inc_sp(&mut self) { |
| 85 | self.sp = self.sp.wrapping_add(1); |
| 86 | } |
| 87 | |
| 88 | pub fn dec_sp(&mut self) { |
| 89 | self.sp = self.sp.wrapping_sub(1); |
| 90 | } |
| 91 | |
| 92 | pub fn halt(&mut self) { |
| 93 | self.halted = true; |
| 94 | } |
| 95 | |
| 96 | pub fn mov_ri(&mut self, mem: &Memory) { |
| 97 | let reg = mem.read(self.pc); |
| 98 | self.inc_pc(); |
| 99 | let val = mem.read(self.pc); |
| 100 | self.inc_pc(); |
| 101 | |
| 102 | match reg { |
| 103 | 0 => self.a = val, |
| 104 | 1 => self.b = val, |
| 105 | 2 => self.c = val, |
| 106 | 3 => self.d = val, |
| 107 | _ => {} |
| 108 | } |
| 109 | |
| 110 | self.zero = val == 0; |
| 111 | } |
| 112 | |
| 113 | pub fn mov_rr(&mut self, mem: &Memory) { |
| 114 | let dest = mem.read(self.pc); |
| 115 | self.inc_pc(); |
| 116 | let src = mem.read(self.pc); |
| 117 | self.inc_pc(); |
| 118 | |
| 119 | let val = self.get_reg(src); |
| 120 | self.set_reg(dest, val); |
| 121 | |
| 122 | self.zero = val == 0; |
| 123 | } |
| 124 | |
| 125 | pub fn add_rr(&mut self, mem: &Memory) { |
| 126 | let dest = mem.read(self.pc); |
| 127 | self.pc += 1; |
| 128 | let src = mem.read(self.pc); |
| 129 | self.pc += 1; |
| 130 | |
| 131 | let (result, carry) = match (dest, src) { |
| 132 | (0, 0) => self.a.overflowing_add(self.a), |
| 133 | (0, 1) => self.a.overflowing_add(self.b), |
| 134 | (0, 2) => self.a.overflowing_add(self.c), |
| 135 | (0, 3) => self.a.overflowing_add(self.d), |
| 136 | |
| 137 | (1, 0) => self.b.overflowing_add(self.a), |
| 138 | (1, 1) => self.b.overflowing_add(self.b), |
| 139 | (1, 2) => self.b.overflowing_add(self.c), |
| 140 | (1, 3) => self.b.overflowing_add(self.d), |
| 141 | |
| 142 | (2, 0) => self.c.overflowing_add(self.a), |
| 143 | (2, 1) => self.c.overflowing_add(self.b), |
| 144 | (2, 2) => self.c.overflowing_add(self.c), |
| 145 | (2, 3) => self.c.overflowing_add(self.d), |
| 146 | |
| 147 | (3, 0) => self.d.overflowing_add(self.a), |
| 148 | (3, 1) => self.d.overflowing_add(self.b), |
| 149 | (3, 2) => self.d.overflowing_add(self.c), |
| 150 | (3, 3) => self.d.overflowing_add(self.d), |
| 151 | |
| 152 | _ => (0, false), |
| 153 | }; |
| 154 | |
| 155 | match dest { |
| 156 | 0 => self.a = result, |
| 157 | 1 => self.b = result, |
| 158 | 2 => self.c = result, |
| 159 | 3 => self.d = result, |
| 160 | _ => {} |
| 161 | } |
| 162 | |
| 163 | self.zero = result == 0; |
| 164 | self.carry = carry; |
| 165 | } |
| 166 | pub fn add_ri(&mut self, mem: &Memory) { |
| 167 | let dest = mem.read(self.pc); |
| 168 | self.pc += 1; |
| 169 | let imm = mem.read(self.pc); |
| 170 | self.pc += 1; |
| 171 | |
| 172 | let (result, carry) = match dest { |
| 173 | 0 => self.a.overflowing_add(imm), |
| 174 | 1 => self.b.overflowing_add(imm), |
| 175 | 2 => self.c.overflowing_add(imm), |
| 176 | 3 => self.d.overflowing_add(imm), |
| 177 | _ => (0, false), |
| 178 | }; |
| 179 | |
| 180 | match dest { |
| 181 | 0 => self.a = result, |
| 182 | 1 => self.b = result, |
| 183 | 2 => self.c = result, |
| 184 | 3 => self.d = result, |
| 185 | _ => {} |
| 186 | } |
| 187 | |
| 188 | self.zero = result == 0; |
| 189 | self.carry = carry; |
| 190 | } |
| 191 | |
| 192 | pub fn sub_rr(&mut self, mem: &Memory) { |
| 193 | let dest = mem.read(self.pc); |
| 194 | self.pc += 1; |
| 195 | let src = mem.read(self.pc); |
| 196 | self.pc += 1; |
| 197 | |
| 198 | let (result, borrow) = match (dest, src) { |
| 199 | (0, 0) => self.a.overflowing_sub(self.a), |
| 200 | (0, 1) => self.a.overflowing_sub(self.b), |
| 201 | (0, 2) => self.a.overflowing_sub(self.c), |
| 202 | (0, 3) => self.a.overflowing_sub(self.d), |
| 203 | |
| 204 | (1, 0) => self.b.overflowing_sub(self.a), |
| 205 | (1, 1) => self.b.overflowing_sub(self.b), |
| 206 | (1, 2) => self.b.overflowing_sub(self.c), |
| 207 | (1, 3) => self.b.overflowing_sub(self.d), |
| 208 | |
| 209 | (2, 0) => self.c.overflowing_sub(self.a), |
| 210 | (2, 1) => self.c.overflowing_sub(self.b), |
| 211 | (2, 2) => self.c.overflowing_sub(self.c), |
| 212 | (2, 3) => self.c.overflowing_sub(self.d), |
| 213 | |
| 214 | (3, 0) => self.d.overflowing_sub(self.a), |
| 215 | (3, 1) => self.d.overflowing_sub(self.b), |
| 216 | (3, 2) => self.d.overflowing_sub(self.c), |
| 217 | (3, 3) => self.d.overflowing_sub(self.d), |
| 218 | |
| 219 | _ => (0, false), |
| 220 | }; |
| 221 | |
| 222 | match dest { |
| 223 | 0 => self.a = result, |
| 224 | 1 => self.b = result, |
| 225 | 2 => self.c = result, |
| 226 | 3 => self.d = result, |
| 227 | _ => {} |
| 228 | } |
| 229 | |
| 230 | self.zero = result == 0; |
| 231 | self.carry = borrow; |
| 232 | } |
| 233 | |
| 234 | pub fn sub_ri(&mut self, mem: &Memory) { |
| 235 | let dest = mem.read(self.pc); |
| 236 | self.pc += 1; |
| 237 | let imm = mem.read(self.pc); |
| 238 | self.pc += 1; |
| 239 | |
| 240 | let (result, borrow) = match dest { |
| 241 | 0 => self.a.overflowing_sub(imm), |
| 242 | 1 => self.b.overflowing_sub(imm), |
| 243 | 2 => self.c.overflowing_sub(imm), |
| 244 | 3 => self.d.overflowing_sub(imm), |
| 245 | _ => (0, false), |
| 246 | }; |
| 247 | |
| 248 | match dest { |
| 249 | 0 => self.a = result, |
| 250 | 1 => self.b = result, |
| 251 | 2 => self.c = result, |
| 252 | 3 => self.d = result, |
| 253 | _ => {} |
| 254 | } |
| 255 | |
| 256 | self.zero = result == 0; |
| 257 | self.carry = borrow; |
| 258 | } |
| 259 | |
| 260 | pub fn jmp(&mut self, mem: &Memory) { |
| 261 | let low = mem.read(self.pc) as u16; |
| 262 | self.inc_pc(); |
| 263 | let high = mem.read(self.pc) as u16; |
| 264 | self.inc_pc(); |
| 265 | |
| 266 | let addrs = (high << 8) | low; |
| 267 | |
| 268 | self.pc = addrs; |
| 269 | } |
| 270 | |
| 271 | pub fn jz(&mut self, mem: &Memory) { |
| 272 | let low = mem.read(self.pc) as u16; |
| 273 | self.inc_pc(); |
| 274 | let high = mem.read(self.pc) as u16; |
| 275 | self.inc_pc(); |
| 276 | |
| 277 | let addrs = (high << 8) | low; |
| 278 | |
| 279 | if self.zero { |
| 280 | self.pc = addrs; |
| 281 | } |
| 282 | } |
| 283 | |
| 284 | pub fn jnz(&mut self, mem: &Memory) { |
| 285 | let low = mem.read(self.pc) as u16; |
| 286 | self.inc_pc(); |
| 287 | let high = mem.read(self.pc) as u16; |
| 288 | self.inc_pc(); |
| 289 | |
| 290 | let addrs = (high << 8) | low; |
| 291 | |
| 292 | if !self.zero { |
| 293 | self.pc = addrs; |
| 294 | } |
| 295 | } |
| 296 | |
| 297 | pub fn cmp_rr(&mut self, mem: &Memory) { |
| 298 | let r1 = mem.read(self.pc); |
| 299 | self.inc_pc(); |
| 300 | let r2 = mem.read(self.pc); |
| 301 | self.inc_pc(); |
| 302 | |
| 303 | let v1 = self.get_reg(r1); |
| 304 | let v2 = self.get_reg(r2); |
| 305 | |
| 306 | let (result, borrow) = v1.overflowing_sub(v2); |
| 307 | |
| 308 | self.zero = result == 0; |
| 309 | self.carry = borrow; |
| 310 | } |
| 311 | |
| 312 | pub fn cmp_ri(&mut self, mem: &Memory) { |
| 313 | let r1 = mem.read(self.pc); |
| 314 | self.inc_pc(); |
| 315 | let r2 = mem.read(self.pc); |
| 316 | self.inc_pc(); |
| 317 | |
| 318 | let v1 = self.get_reg(r1); |
| 319 | |
| 320 | let (result, borrow) = v1.overflowing_sub(r2); |
| 321 | |
| 322 | self.zero = result == 0; |
| 323 | self.carry = borrow; |
| 324 | } |
| 325 | |
| 326 | pub fn mul(&mut self, mem: &Memory) { |
| 327 | let dest = mem.read(self.pc); |
| 328 | self.inc_pc(); |
| 329 | let src = mem.read(self.pc); |
| 330 | self.inc_pc(); |
| 331 | |
| 332 | let lhs = self.get_reg(dest); |
| 333 | let rhs = self.get_reg(src); |
| 334 | |
| 335 | let result16 = (lhs as u16) * (rhs as u16); |
| 336 | let result8 = (result16 & 0xFF) as u8; |
| 337 | |
| 338 | self.set_reg(dest, result8); |
| 339 | |
| 340 | self.zero = result8 == 0; |
| 341 | self.carry = result16 > 0xFF; |
| 342 | } |
| 343 | |
| 344 | pub fn div(&mut self, mem: &Memory) { |
| 345 | let dest = mem.read(self.pc); |
| 346 | self.inc_pc(); |
| 347 | let src = mem.read(self.pc); |
| 348 | self.inc_pc(); |
| 349 | |
| 350 | let lhs = self.get_reg(dest); |
| 351 | let rhs = self.get_reg(src); |
| 352 | |
| 353 | if rhs == 0 { |
| 354 | panic!("Division by zero"); |
| 355 | // OR: set halted = true |
| 356 | // OR: define a syscall/exception later |
| 357 | } |
| 358 | |
| 359 | let result = lhs / rhs; |
| 360 | |
| 361 | self.set_reg(dest, result); |
| 362 | |
| 363 | self.zero = result == 0; |
| 364 | // carry unchanged |
| 365 | } |
| 366 | |
| 367 | pub fn call(&mut self, mem: &mut Memory) { |
| 368 | let low = mem.read(self.pc) as u16; |
| 369 | self.inc_pc(); |
| 370 | let high = mem.read(self.pc) as u16; |
| 371 | self.inc_pc(); |
| 372 | let addr = (high << 8) | low; |
| 373 | |
| 374 | let return_addr = self.pc; |
| 375 | |
| 376 | self.push16(mem, return_addr); |
| 377 | self.pc = addr; |
| 378 | } |
| 379 | |
| 380 | pub fn ret(&mut self, mem: &mut Memory) { |
| 381 | let addr = self.pop16(mem); |
| 382 | self.pc = addr; |
| 383 | } |
| 384 | |
| 385 | pub fn syscall(&mut self, mem: &Memory) { |
| 386 | let num = mem.read(self.pc); |
| 387 | self.pc = self.pc.wrapping_add(1); |
| 388 | match num { |
| 389 | 0 => { |
| 390 | // exit |
| 391 | self.halted = true; |
| 392 | } |
| 393 | 1 => { |
| 394 | // print A as number |
| 395 | println!("{}", self.a); |
| 396 | } |
| 397 | 2 => { |
| 398 | // print A as ASCII char |
| 399 | print!("{}", self.a as char); |
| 400 | } |
| 401 | _ => panic!("Unknown syscall {}", num), |
| 402 | } |
| 403 | } |
| 404 | |
| 405 | fn get_reg(&self, r: u8) -> u8 { |
| 406 | match r { |
| 407 | 0 => self.a, |
| 408 | 1 => self.b, |
| 409 | 2 => self.c, |
| 410 | 3 => self.d, |
| 411 | _ => panic!("Invalid Register"), |
| 412 | } |
| 413 | } |
| 414 | |
| 415 | fn set_reg(&mut self, dest: u8, val: u8) { |
| 416 | match dest { |
| 417 | 0 => self.a = val, |
| 418 | 1 => self.b = val, |
| 419 | 2 => self.c = val, |
| 420 | 3 => self.d = val, |
| 421 | _ => panic!("Invalid register"), |
| 422 | } |
| 423 | } |
| 424 | } |