5DATA COMMUNICATION USING THE MELSEC COMMUNICATION PROTOCOL

MELSEC-Q

5 DATA COMMUNICATION USING THE MELSEC COMMUNICATION PROTOCOL

This chapter explains an overview of the MELSEC communication protocol (hereinafter abbreviated as the MC protocol). See the following manual for a detailed explanation of the data communication functions that are available when using the MC protocol.

Q Corresponding MELSEC Communication Protocol Reference Manual (SH-080008)

5.1 Data Communication Functions

The MELSEC protocol (MC protocol) is a communication system for the Q series PLCs. Using this protocol, the external devices can read or write device data and programs for the PLC CPUs via the Q series C24 or Q series Ethernet interface module.

Any external devices on which application programs can be installed and which can transmit and receive data in accordance with the MELSEC PLC protocol can communicate with the PLC CPUs using the MC protocol.

5.1.1 Accessing the PLC CPUs using the MC protocol

 

This section describes the main functions for accessing the PLC CPUs using the

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MC protocol.

 

 

(An overview of the data communication functions using the MC protocol is

 

 

provided in Section 3.4).

 

 

With the exception of the on-demand function described below, the Q series C24

 

 

sends and receives data based on commands from the external devices.

 

 

Thus, the PLC CPU side does not require sequence programs for data

 

 

communication.

 

(1)

Data read/write

 

 

This function reads and writes data from/to the PLC CPU device memory of the

 

 

local-station or other station on the MELSECNET/H, MELSECNET/10 as well as

 

 

the intelligent function module buffer memory.

 

 

By reading and writing data, the PLC CPU operation monitoring, data analysis and

 

 

production management can be performed on the external device side.

 

 

Also, production directions can be executed on the external device side.

 

(2)

File read/ write

 

 

This function reads and writes files stored in the PLC CPU such as sequence

 

 

programs and parameter files. By reading and writing files, file management for

 

 

the GX Configurator-SC and the QnACPUs of other stations can be performed

 

 

on the external station side.

 

 

Also, execution programs can be changed (replaced) from the external device side.

 

(3) Remote control of the PLC CPU

This function executes remote RUN/STOP/PAUSE/latch clear/reset operations. Remote operations of the PLC CPU can be performed from the external device side using the PLC CPU remote control function.

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