Hitachi HIDIC MICRO-EH Applications Manual page 243

9.3 Instantaneous Power Failure
The following shows operation when the power supply to the MICRO-EH shuts off.
AC power supply
Internal 5 V DC
Internal reset
24 V DC
ON
RUN
OFF
MICRO-EH operation
Power on
2 s
(1) Powering on
The MICRO-EH starts operations after a maximum of 3.5 seconds have elapsed after power-up. If the power for
input module is not completely started when the operation is commenced, the input that is supposed to be on will
be received as Off and operation proceeds, so make sure that the power for I/O module is completely turned on
before operation is commenced.
Note: When extending with a CPU larger than 14-point type, turn on the power supply for both base and
extension sides at the same time.
(2) Instantaneous power failure actions
(a) When 100 VAC is supplied
Operation is continued during instantaneous power failures that last less than 10 ms.
(b) When 200 VAC is supplied
Operation is continued during instantaneous power failure that last less than 20 ms.
Note: Make arrangement so that the power for input module is supplied while the CPU continues its operation. If
the power is not supplied, the CPU will perform operation assuming the input data as Off. Exercise caution
especially when performing operation that changes the contents of the power failure memory using input
signals, since the contents of the power failure memory may have been altered unintentionally due to an
instantaneous power failure.
STOP status
Reset processing
1.0 s
1.2 s
9-10
Chapter 9 PLC Operation
Instantaneous power failure
RUN status
(Starts operation)
When power supply of 100 V AC is used:
operation continues for 10 ms or less
When power supply of 200 V AC is used:
operation continues for 20 ms or less