Java Reference
In-Depth Information
The method
execute()
derives from the straightforward application of the
procedure presented in Sidebar 5.2 to the FSA shown in Figure 5.8.
public void
execute() {
switch
(state){
case
FETCH_entry:
bus.command
#
RAM.RAM_READ;
bus.address
#
PC;
state
!!
;
case
FETCH:
if
(bus.command.equals(RAM.ACK))
state
#
DECODE_entry;
break
;
case
DECODE_entry:
IR
#
bus.data;
PC
!!
;
state
!!
;
case
DECODE:
if
(code(IR).equals(HALT))
state
#
EXEC_HALT_entry;
if
(code(IR).equals(JUMP))
state
#
EXEC_JUMP_entry;
if
(code(IR).equals(JUMPZ))
state
#
EXEC_JUMPZ_entry;
if
(code(IR).equals(LOADA))
state
#
EXEC_LOADA_entry;
if
(code(IR).equals(LOADB))
state
#
EXEC_LOADB_entry;
if
(code(IR).equals(STOREA))
state
#
EXEC_STOREA_entry;
if
(code(IR).equals(STOREB))
state
#
EXEC_STOREB_entry;
if
(code(IR).equals(MOVEAB))
state
#
EXEC_MOVEAB_entry;
if
(code(IR).equals(ADD))
state
#
EXEC_ADD_entry;
break
;
case
EXEC_HALT_entry:
state
!!
;
case
EXEC_HALT:
break
;
case
EXEC_JUMP_entry:
PC
#
arg(IR);
state
!!
;
case
EXEC_JUMP:
state
#
FETCH_entry;
break
;
