TEST CIRCUIT FOR MICROCOMPUTER

PURPOSE:To simplify a program and to increase program executing speed by storing the data and the control signals into a shift register without using a data bus, an accumulator, etc., and then outputting these data and signals directly and serially via a serial output terminal when the working function of an arithmetic logic unit ALU is tested. CONSTITUTION:When the working function of an ALU 1 is tested, the digital data DATA Y and X and the ALU control signals are directly stored in the 1st-3rd shift register 2-4 via a serial application terminal 11 without using a data bus and an accumulator. At the same time, the computing results stored in both registers 6 and 7 are directly and serially outputted via a serial output terminal 20 without using a data bus and an accumulator. Thus it is not required to use a program instruction for the production of the ALU control signal. As a result, the number of program steps is decreased and a program is simplified. Then the program executing speed is increased.