| 摘要 |
PROBLEM TO BE SOLVED: To easily detect malfunction independently of internal circuit without increasing circuit size by inputting the output signal of a boundary scan register in the output buffer of an input output I/O cell. SOLUTION: An input output I/O cell 22 has an input buffer 22a and an output buffer 22b and the input signal from the input output terminal. PAD is input in the input buffer 22a. In the output buffer 22b, a reverse signal PO<-> output from the multiplexer 18 of boundary scan register 10 is input, a control signal is input in the output control terminal and its output signal is input in the input buffer 22a. In this manner, the output buffer 22b of essentially unused input output I/O cell 22 is used as a part of constitution element of the boundary scan register 10 and so the circuit size of the boundary scan register 10 does not increase. By this, detection of malfunction can be easily done by logically separating from the internal circuit. |
