| 摘要 |
PROBLEM TO BE SOLVED: To detect a short-circuit state of an external output terminal without an output from an output buffer, thereby protecting a circuit element more surely. SOLUTION: An output terminal 3 of an output buffer 2 is connected to a pull-up circuit 4 and a pull-down circuit 5. In the first state where a signal output from the output buffer 2 is turned off, the pull-up circuit 4 is turned on, and the pull-down circuit 5 is turned off, if an input level of the output buffer 2 is in a high state, it is determined that the output terminal 3 is not short-circuited to a grounding line. In the second state where the signal output from the output buffer 2 is turned off, the pull-up circuit 4 is turned off, and the pull-down circuit 5 is turned on, if the input level of the output buffer 2 is in a low state, it is determined that the output terminal 3 is not short-circuited to a power supply line. Thus, the short-circuiting state of the output terminal 3 is detected, without actually making an output from the output buffer 2. COPYRIGHT: (C)2009,JPO&INPIT
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