PURPOSE: To facilitate production of programs by comparing an address delivered from a microcomputer with an address set optionally and producing a synchronizing signal when coincidence is obtained between both addresses.

CONSTITUTION: A ROM emulator serving as an aiding device for production of programs of a target microcomputer TμC is provided with a ROM storing the programs of the TμC, a RAM 33 which is replaced with said ROM and a comparator 41. Selectors 36, 37 and 38 are controlled by the selection signal SEL sent from a host CPU, and one of the address signal, the read control signal RD and the chip selection signal CS sent from the TμC is selected at the host side and supplied to the RAM 33. The comparator 41 compares the optional address information given from the host side with the address given from the TμC side and delivers a synchronizing signal when the coincidence is obtained between both addresses. Then the signal is delivered through a terminal 42 as a trigger signal for observation of waveform or timing check.