Communication Structure; Data Communication Procedures - Mitsubishi Electric MELSEC iQ-RJ71EN71 User Manual

Communication structure

When a message is sent from the external device to the Ethernet-equipped module using the SLMP message format, the
Ethernet-equipped module executes a processing corresponding to the received message. During communication, the
Ethernet-equipped module functions as a server and the external device (terminals such as a personal computer) functions as
the client. The server (Ethernet-equipped module) automatically returns a response message suitable for the request
message received from the client.
(1)
Ethernet
(1) Server side: Ethernet-equipped module
(2) Client side: External device

Data communication procedures

This section describes the procedures for communicating with SLMP.
1.
After the module parameters are set, the system checks that the initial processing of the Ethernet-equipped module has
ended normally. ('Initial status' (Un\G1900024.0): On)
2.
Perform the open processing to establish a connection between the Ethernet-equipped module and external device.
( Page 378 TCP/IP Communications, UDP/IP Communications)
3.
After the connection is established, the SLMP messages are sent from the external device.
4.
Close the connection when communication is finished.
In the following case, the Ethernet-equipped module performs a remote password check when the external
device is accessing the programmable controller. If communication is not possible, unlock the remote
password. ( Page 177 Access permit processing (Unlock processing))
• When remote password is set for the CPU module.
• When connection for exchanging data with external device is set as a remote password check target.
1 FUNCTIONS
28
1.2 SLMP Communications
Request message
Access
Header Subheader
destination
Response message
Header Subheader
(2)
Command
Response data