| 摘要 |
PURPOSE:To recognize a communication line including a line adaptor whose address comparator is faulty by means of a supervisory device by providing a diagnostic section in a frame to diagnose the address comparator. CONSTITUTION:A frame to be transmitted is provided with a diagnostic part including a test time slot TTS and a counter part CNT in a data highway system where the supervisory device SV and plural communication devices are connected by a ring data transmission line. The SV sets a time slot TS to the TTS, zeros the CNT to transmit a frame. A communication device receiving the frame uses a frame counter 10 to detect the TTS and inform the TS to a register 17. The address comparator AC 12 compares the transmitted TS with the TS assigned from the SV in advance and when they are coincident, the result is informed to a counter revision section 18. The revision section 18 revises the count, and the value is inserted to the CNT via a P/S section 8, the frame is circulated and returned to the SV. When the CNT is not matched to an expected value, the SV recognizes it as a line adaptor having an AC fault.
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