Precautions - Mitsubishi Electric MELSEC iQ-RJ71EN71 User Manual

Precautions

This section provides precautions for the simple CPU communication function.
Incomplete data reception and timeout
Because the load of Ethernet communication becomes heavy during the simple CPU communication, if the other
communication (MELSOFT connection or SLMP) is simultaneously performed by using UDP, the data reception of UDP may
not be completed, resulting in a timeout error. Therefore, to perform other communications during the simple CPU
communication, the communication using TCP is recommended.
Execution interval setting
The execution interval of the simple CPU communication function will differ according to the Ethernet line's load rate,
operating status of other communications (such as MELSOFT connection, SLMP communication, and socket communication
function), scan time of the communication destination, and system configuration. Thus, the set execution interval or time
required for completing the communications may be increased.
■Cause of increased execution interval of the simple PLC communication
• The scan time of the control CPU module of the RJ71EN71 where the simple CPU communication function is set is long.
• The RJ71EN71 where the simple CPU communication function is set is communicating by using a function other than the
simple CPU communication function, and the processing of the communication by using a function other than the simple
CPU communication function takes time.
• The load on the Ethernet line is high.
• The number of settings in "Simple CPU Communication Setting" under "Application Settings" is large.
• Response from the communication destination is delayed.
• More than one RJ71EN71 where the simple CPU communication function is set is mounted on a base unit (main base unit
or extension base unit).
To perform communications at the set execution interval, set a sufficient execution interval. If checking the execution interval
is required, perform actual communications and check it with the "Simple PLC Communication Diagnostics" window.
Duplication of own station port numbers
The simple CPU communication cannot be performed in the following cases.
• The own station port number set in the simple CPU communication and the own station port number of the CPU module set
in the external device configuration are the same.
• The own station port number set in the simple CPU communication and the one set in another function such as the socket
communication are the same. ('Simple CPU communication status for each setting number' (Un\G721936 to Un\G721999)
is "AH: Communications impossible". )
Set a unique own station port number. For the setting numbers other than the one in which a communication error occurs,
communications are performed after the preparation processing is completed normally.
IP address and module type of the external device
Check the IP address and module type of the communication destination device before setting the parameters. The simple
CPU communication cannot be performed when the communication destination does not exist (an incorrect IP address is
specified) or when the preparation processing is not completed. ('Simple CPU communication status for each setting number'
(Un\G721936 to Un\G721999) is "AH: Communications impossible". )
Communication destination device
Check the type or range of the device to be read or written in the communication destination.
Especially, when "Write" is set for the communication pattern, since the control data of the communication destination may be
overwritten, communications may result in malfunction.
1.15 Simple CPU Communication Function (RJ71EN71, RnENCPU (Network Part))
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