Notes On The System Configuration - Mitsubishi MELSEC-Q Series User Manual

2 SYSTEM CONFIGURATION

2.2.2 Notes on the system configuration

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The system should be designed with the following considerations to prevent mis-input
from the remote I/O modules:
(1) When powering on and off
Start the data link after turning on the power to the remote I/O modules. Turn off
the power to the remote I/O modules after stopping the data link.
Master module
(data link status)
Remote I/O module
(power status)
(2) During momentary power failure of the remote I/O modules
When a momentary power failure occurs in the power (24 V DC) being supplied
to the remote I/O modules, mis-input may occur.
(a) Cause for mis-input due to a momentary power failure
The remote I/O module hardware uses the power by internally converting
the module power (24 V DC) to 5 V DC.
When a momentary power failure occurs in a remote I/O module, the
following condition occurs:
(Time for the 5 V DC power in the remote I/O module to turn off) >
(Response time for input module on
Therefore, mis-input occurs when a refresh is performed within the time
indicated by 1) in the figure below.
Remote I/O module
(module power supply and input
external supply power)
Remote I/O module (internal 5 V DC)
Input (Xn)
Data link start
During operation
During stop
ON
OFF
off)
When the input external power supply turns OFF, the
input (Xn) turns OFF after the response time for the
input module to change from ON to OFF.
MELSEC-Q
Data link stop
1)
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