7 Communication Using MC Protocol
50
FX
3U
-ENET-ADP User's Manual
7.3 Message Formats and Control Procedures
7.2.5
Precautions on Data Communication
This section explains some precautions that should be observed when performing data communication
between an external device and the Ethernet adapter.
• Reading/writing data when the Ethernet adapter status is as follows
Data communication using the MC protocol from the external device is enabled without regard to the
absence/presence of a sequence program when the FX
3U
-ENET-ADP unit ready signal (M8404 and
M8424, refer to Appendix A for details) is ON and the opening completion signal (corresponding bit of
D8406 and D8426, refer to Appendix A for details) for the used connection is ON (1: Open).
• Data communication using the MC protocol is enabled only when the open system in the open setting
(refer to Section 6.11) is set to "MC protocol". (For operation of GX Works2, refer to Section 8.2.)
• Replacing the Ethernet adapter
The Ethernet address (MAC address) differs depending on the device.
When the Ethernet adapter is replaced due to breakdown, reboot any external devices also.
Similarly, reboot the Ethernet adapter even when an external device is replaced (such as a personal
computer).
7.3
Message Formats and Control Procedures
This section explains the message format and control procedure for each command when data
communication is performed using A compatible 1E frames.
The MC protocol for the Ethernet adapter is a subset of A compatible 1E frames.
Both TCP/IP and UDP can be used as lower layer protocol and support both ASCII code and binary code.
7.3.1
How to read the command reference section
The following explains how to read the message explanation diagrams shown in each of the command
description Section 7.5 through 7.7.
1) When an external device reads data from the PLC
a) Area A indicates transmission from the external device to the PLC.
b) Area B indicates transmission from the PLC to the external device.
c) The program of the external device is generated so that the data is transmitted sequentially from left to
right. (For example: in case of area A, data should be sequentially sent starting from the header.)
(Command message)
External
device side
Header
Subheader
PC No.
Monitoring timer
PLC side
Header
Subheader
Co
m
pl
et
e c
od
e
Area B
(Response message)
Area A
Summary of Contents for FX3U-ENET-ADP
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