| 摘要 |
PURPOSE:To reduce remarkably the leakage of checking of runaway by collating the contents of a memory for storing check data every period, and only when the prescribed check data are stored, sending a watchdog pulse. CONSTITUTION:When a pushbutton telephone set 1 is polled, a CPU 14 transmits/receives data to/from a master device, and then executes the processing of the received data. The CPU 14 sets up the least significant bit of a 4-bit watchdog in a variable memory 15B to '1', and at the time of transmission, executes the output processing and sets up the 2nd lower bit of the watchdog to '1'. When all the contents of the watchdog area are '1' after executing similar output processing successively, a watchdog pulse is generated. Namely, one pulse is sent every transmission period, and only when all check bits are written, i.e. only when all processing has been passed, the pulse is sent. When any one of processing is missed, no pulse is outputted, so that the leakage of checking of runaway can be reduced.
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