Exemple #1
0
func (c *CPU) decode() {
	switch vm.Opcode(c.ir & 0x3f) {
	case vm.NOP:
	case vm.CALL:
	case vm.JMP, vm.JPZ, vm.JNZ:
	case vm.RET:
		c.sp--
		c.ar = c.sp
		c.dr = c.mem.Fetch(c.ar)
		c.sp--
		c.ar = c.sp
	case vm.POP:
		c.sp--
		c.ar = c.sp
	case vm.PUSH:
		c.dr = c.ac
		c.ar = c.sp
		c.sp++
	case vm.MVR:
		c.dr = c.ac
	case vm.MVI:
	case vm.MOV, vm.ADD, vm.DIV, vm.MUL, vm.SHL, vm.SHR, vm.SUB, vm.AND, vm.OR:
		switch vm.Register(c.ir & 0xc0) {
		case vm.REGB:
			c.dr = c.b
		case vm.REGC:
			c.dr = c.c
		}
	case vm.INC:
		c.dr = 1
	}
}
Exemple #2
0
func (c *CPU) fetch() {
	// cycle 1
	c.ar = c.pc              // set address register to the program counter
	c.pc++                   // advance the program counter
	c.dr = c.mem.Fetch(c.ar) // fetch instruction into data register
	c.ir = c.dr              // set the instruction register to the data register
	//fmt.Println("c.ar:", c.ar, "c.ir:", c.ir)

	switch vm.Opcode(c.ir) {
	case vm.CALL: // cycle 2 and 3
		// load address to jump to
		c.dr = c.mem.Fetch(c.pc)
		c.pc++
		c.tr = c.dr
		c.dr = c.mem.Fetch(c.pc)
		c.pc++
	case vm.JMP, vm.JPZ, vm.JNZ: // cycle 2 and 3
		c.dr = c.mem.Fetch(c.pc)
		c.ar = uint16(c.dr) << 8
		c.pc++
		c.dr = c.mem.Fetch(c.pc)
		c.ar |= uint16(c.dr)
		c.pc++
	case vm.MVI: // cycle 2
		c.dr = c.mem.Fetch(c.pc)
		c.pc++
	}
}
Exemple #3
0
func (c *CPU) exec() {
	switch vm.Opcode(c.ir & 0x3f) {
	case vm.NOP:
	case vm.JMP:
		c.pc = c.ar
	case vm.JPZ:
		if c.zero {
			c.pc = c.ar
		}
	case vm.JNZ:
		if !c.zero {
			c.pc = c.ar
		}
	case vm.CALL:
		c.ar = c.sp
		c.sp++
		c.mem.Write(c.ar, uint8(c.pc))
		c.ar = c.sp
		c.sp++
		c.mem.Write(c.ar, uint8(c.pc>>8))
		c.pc = uint16(c.tr) << 8
		c.pc |= uint16(c.dr)
	case vm.RET:
		c.pc = uint16(c.dr) << 8
		c.dr = c.mem.Fetch(c.ar)
		c.pc |= uint16(c.dr)
	case vm.MOV:
		c.ac = c.dr
	case vm.MVR:
		switch vm.Register(c.ir & 0xc0) {
		case vm.REGB:
			c.b = c.dr
		case vm.REGC:
			c.c = c.dr
		}
	case vm.MVI:
		c.ac = c.dr
	case vm.CLA:
		c.ac = 0
		c.zero = true
	case vm.CLR:
		c.ac = 0
	case vm.POP:
		c.dr = c.mem.Fetch(c.ar)
		c.ac = c.dr
	case vm.PUSH:
		c.mem.Write(c.ar, c.dr)
	case vm.ADD, vm.INC:
		c.ac += c.dr
	case vm.DIV:
		c.ac /= c.dr
	case vm.MUL:
		c.ac *= c.dr
	case vm.SHL:
		c.ac <<= c.dr
	case vm.SHR:
		c.ac >>= c.dr
	case vm.SUB:
		c.ac -= c.dr
	case vm.AND:
		c.ac &= c.dr
	case vm.OR:
		c.ac |= c.dr
	}
}