Mitsubishi MELSEC L Series, User Manual

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CHAPTER 5 MC PROTOCOL COMMUNICATION
5
5.
3
P
recaut
ions
5.3
Precautions
(1) Number of devices
Only the external devices whose open system is set to "MC Protocol" can be connected concurrently using MC
protocol.
Project window [Parameter] [PLC Parameter] [Built-in Ethernet Port Setting]
[Open Setting]
(2) Data communication frame
The QnA-compatible 3E frames only are applicable to CPU modules.
(3) Access range
• Only the connected CPU module can be accessed. Accessing another module will cause an error.
• Accessing another station on a network such as CC-Link is not allowed via the connected CPU module.
(4) When UDP is selected for Protocol
• If a new request message is sent to a UDP port after the previous request message is sent to the same port
and before no response is returned, the new request message will be discarded.
• Setting the same host station port number for multiple UDP connections is regarded as one setting. For
communication with multiple devices using the same host station port number, select TCP.
(5) File access during MC communication
The CPU module will perform file access processing prior to Ethernet communication processing. Because of
this, processing of the MC protocol function may be delayed if a file is accessed by FTP or a programming tool
during use of the MC protocol function.
When accessing a file while response time monitoring is performed on the connected device with the MC protocol
function, add the time required for file access to the monitoring time.