| 摘要 |
PURPOSE:To facilitate a test, by providing MOSFET on the signal line connecting the microprocessor function and peripheral LSI function in LSI and connecting a diagnostic circuit to the output side of said MOSFET through MOSFET. CONSTITUTION:Transfer MOSFET 20 is provided on the signal wire connecting the microprocessor function block 1 and peripheral LSI function block 2 in one LSI 10 and a diagnostic circuit 3 is connected to the output side of MOSFET 20 through transfer MOSFET 30. At the time of normal operation, because MOSFET 20 comes to a continuity state to cut off MOSFET 30, the transmission and reception of a signal is performed between blocks 1, 2 and microprocessor and peripheral LSI functions are operated. At the time of diagnosis, because MOSFET 20 is cut off and MOSFET 30 comes to a continuity state, the microprocessor and peripheral LSI functions are cut off from peripheral circuits and the input and output from the circuit 3 becomes possible. Therefore, a microprocessor or peripheral LSI coming to a target can be tested alone and easily from the circuit 3.
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