def dispatch(self):
""" Execute instruction at [PC] """
instruction = self.cpu.ram[self.cpu.PC.value].value
self.cpu.PC.value = self.cpu.PC.value + 1
op_code, b_val, a_val = unpack_instruction(instruction)
if op_code == 0x00:
self.non_basic(instruction)
else:
b = value_lookup(self.cpu, b_val, as_a=False)
a = value_lookup(self.cpu, a_val, as_a=True)
if not self.cpu.skip_instruction:
self.BASIC_INSTRUCTIONS[op_code](b, a)
else:
self.cpu.skip_instruction = False
def non_basic(self, instruction):
opcode, a_val = unpack_special_instruction(instruction)
if(opcode != OPCODE.JSR):
return
a = value_lookup(self.cpu, a_val, as_a=True)
if self.cpu.skip_instruction:
self.cpu.skip_instruction = False
return
# Push next address to the stack
if self.cpu.SP.value < 0:
self.halt('Stack overflow')
self.cpu.SP.value -= 1
self.cpu.ram[self.cpu.SP.value].value = self.cpu.PC.value
self.cpu.PC.value = a.value
