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MELSEC-Q
5 DATA COMMUNICATION USING THE MELSEC COMMUNICATION
PROTOCOL
5
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
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.