To provide a program execution system which can be rewritten by software and operated even without a reset signal having various addressing modes though a scheduling function is fixed in terms of hardware and has no versatility.
This program execution circuit is constituted of a program counter control means to manage execution of a task, a program counter, a first switching unit to switch program counters and output an execution address, a program storage ROM to output instruction data based on the execution address to be outputted by the switching unit, an index register to hold information to be a base of a signal of an address bus, a second switching device to output a control signal and the signal of the address bus from the contents of the instruction data to be outputted by the program storage ROM and an index register, a port for immediateness to output the contents of the program storage ROM, a multipurpose register to be a transfer object when data transfer is performed, an arithmetic unit, a ROM to hold fixed data, a RAM as a readable/writable memory and an input/output port to perform an interface with the outside.
MURABAYASHI FUMIO
YAMAUCHI TATSUMI
HANZAWA KEIJI
HITACHI CAR ENG CO LTD