Communication Structure; Data Communication Procedure - Mitsubishi Melsec-L Series User Manual

9.2

Communication Structure

When a connected device sends a message to an E71 in the MC protocol message format, the E71 performs the
process according to the message. During communications, a CPU module including the E71 operates as a server,
and the connected device (a personal computer or other terminals) operates as a client. Based on the command
message received from the client, the server (the E71) automatically sends an appropriate response message.
Ethernet
The frames that can be used with an E71 are as follows.
• 4E frame
• QnA-compatible 3E frame
• A-compatible 1E frame
9.3

Data Communication Procedure

The following is a data communication procedure for MC protocol communications.
1.
Set the parameters. (
2.
Perform the open process and establish a connection between the E71 and the connected device.
( Page 70, Section 7.2, Page 78, Section 7.3)
3.
Once the connection is established, the connected device sends an MC protocol message.
4.
The connection is closed after the communications are completed.
In the cases described below, an E71 performs a remote password check when the connected device accesses the
programmable controller. If communications cannot be performed, unlock the remote password. (
12.3.2)
• When a remote password has been set in the CPU module
• When the connection for data communications with the connected device is to be subjected to the remote
password check
Server
E71
Command message
Header
Subheader
Header
Page 86, Section 9.4)
CHAPTER 9 MC PROTOCOL COMMUNICATIONS
Connected device
Application data
Text (command)
Response message
Application data
Subheader Text (command)
Client
Page 141, Section
85
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