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case READ_B_entry:
RegB # bus.getData();
state !! ;
case READ_B:
state # ADD_entry;
break ;
case ADD_entry:
RegA # Integer.toString(
! Integer.parseInt(RegB)
state !! ;
case ADD:
state # WRITE_MEM2_entry;
break ;
case WRITE_MEM2_entry:
state !! ;
case WRITE_MEM2:
if (bus.getCommand().equals(RAM.ACK))
state # HALT_entry;
break ;
case HALT_entry:
state !! ;
case HALT:
break ;
It is important to detect when the CPU enters the halt state, because after
this step the simulation stops. Since the state attribute must remain private,
a function can be used to this purpose.
public boolean halted() { return state ## HALT; }
Let's now refine the implementation of class Computer . The halted method
of the CPU class should be checked in the simulate method in order to stop
the simulation when the CPU enters the HALT state. In addition we define a
constructor that takes as argument the initial content of the memory.
public class Computer {
final Bus bus # new Bus();
final CPU cpu # new CPU(bus);
final RAM ram # new RAM(bus,3);
public Computer(String[] initialMemory){
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