PURPOSE: To generate easily an analog waveform for simulation, by using a microcomputer, a memory and a D/A converter.

CONSTITUTION: A memory 2 is successively addresses with the output signal produced from an output port P1 of a microcomputer CM1, and the reading output of the memory 2 is supplied to an input port P2 of the computer CM1. The output voltage value data is stored in the even address of the memory 2; while the output period data showing each output period of the voltage value data stored in an immediately preceding address is stored in the odd address of the memory 2, respectively. The computer CM1 feeds the output voltage value data stored in the memory 2 to a D/A converter 3 via an output port P3 and for a period corresponding to the output period data. The converter 3 converts the voltage data into the analog value A and delivers it for a period corresponding to the period data. This procedure is carried out while advancing the memory address. As a result, an analog wave for simulation can be produced easily with high reproduibility and with a facilitated alteration.