POWER DOWN CONTROL SYSTEM

摘要

PURPOSE:To surely and effectively execute the power down control. CONSTITUTION:A reference pulse generation circuit 301 generates a first reference pulse S1 and a second reference pulse S3 obtained by frequency division of the pulse S1 based on a synchronizing signal S0. A power down control signal generation circuit 302 generates a power down control signal S2 based on the first reference pulse S1 to periodically perform the power down operation of a RAM 303. A power down monitor circuit 300 detects the control signal S2 at each second reference pulse S3 by a flip flop 304 to detect its normalcy. That is, a signal S4 inverted to me high level is outputted from an output Q2 if the control signal S2 is in the low level because of a fault or the like though having to be in the high level. Then, an alarm AL is sent to a central processing unit or the like, and the power down operation of the RAM 303 is performed through an OR circuit 305. This operation is continued based on reference pulses S1 and S2 when the control signal S2 is abnormal, and the power down operation of the RAM 303 is normally executed.