Precautions For The System Configuration - Mitsubishi Electric MELSEC-Q Series User Manual

5.3

Precautions for the System Configuration

(1) When using the remote station
This section describes notes to be paid attention upon system design to prevent an incorrect input from a remote
station.
(a) When turning on and off the power
Power on the remote station, then start data link. In addition, stop data link before turning off the remote station.
Failure to do so may cause an incorrect input.
Master station
(data link status)
(power supply status)
(b) Upon a momentary power failure of a remote station
If a momentary power failure occurs in the power supply (24VDC) of the remote station, an incorrect input may
occur.
Cause of an incorrect input due to a momentary power failure
•
The hardware of a remote station internally converts the power supply of a module (24VDC) into 5VDC. If
a momentary power failure occurs in a remote station, the time until the 5VDC power supply in the remote
station turns off becomes greater than the response time after an input module turns on and off; therefore,
refreshing data within the time as shown in 1. below causes an incorrect input.
Remote station
(Module power supply and input external
power supply)
Remote station
(Internal 5VDC)
Input (Xn)
72
During
execution
Stopped
ON
Remote station
OFF
Data link starts.
1.
Turning off the input external power supply turns off an input (Xn)
after the response time between the input module turning on and
it turning off.
Data link stops.