| 摘要 |
PURPOSE:To detect disconnection of a signal line at the reception side by providing an inverting element receiving an disconnection check signal and an output data and supplying the output data to a transistor (TR) while not inverting its level when the disconnection check signal is at a 1st level and inverting the data when it is n a 2nd level. CONSTITUTION:An encoder 1- an output buffer are similar to those of a conventional device. In applying disconnection check to a signal wire 5, a disconnection check signal 15 is supplied from a processing circuit 6 and outputted to the encoder 1 via an output buffer 16. An exclusive OR gate 17 receives the output data 2 and the output of the buffer 16 and feeds an output to an AND gate 13 as an inverting element. A CPU 18 is connected to the output of the input buffer 9. Assuming that an encoder output enable signal 11 is at level H. Thus, when the level of the disconnection check signal 15 is switched normally, the input level of the signal line 5 is inverted but the input level of the signal wire is not inverted if the signal wire is opened even if the level of the signal 15 is switched.
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