7 Communication Using MC Protocol
47
FX3U-ENET-ADP User's Manual
1
Introduction
2
Specification
3
System
Configuration
4
Installation
5
Wiring
6
Introduction of
Functions
7
Communication
Using
MC Protocol
8
The Operation
of GX Works2
9
Troubleshooting
A
List of Special
Devices
7.1 Data Codes for Communication
7. Communication Using MC Protocol
This chapter gives an overview of the MC protocol.
The frame type of MC protocol (data communication messages) used by the external device to access the
PLC via this product is equivalent to A compatible 1E frame.
7.1 Data Codes for Communication
This section explains the data codes used in communication between the Ethernet adapter and the external
device or the PLC.
1) The data codes used while communicating are listed below.
a) Ethernet adapter
External device
You can execute data communication by selecting "binary code" or "ASCII code" in GX Works2.
To switch between binary code/ASCII code, refer to Section 6.6.
2) When communicating using ASCII code, 1-byte binary code data is automatically converted into 2-byte
ASCII code data and then transmitted.
(Example)
7.2 Data Communication Function
The MC protocol is the abbreviated name of the MELSEC protocol that is a communication system for the
PLCs. Using this protocol, the external devices can read or write device data from/to the PLC via the Ethernet
adapter.
Any external devices on which application programs can be installed and which can send and receive data in
accordance with the MELSEC PLC protocol can access the PLC using MC Protocol.
L
H
H
Head device
Text (Command)
ACPU
monitoring
timer
PC
No.
Subheader
Header
Ethernet
(14bytes)
IP
(20bytes)
TCP
/
UDP
L
(Command message for A compatible 1E frame)
Number of
device points
00H 0AH 00H
00
H
00
H
00
H
20
H
40
H
0CH 00HFFH
64
H
(Example)
Binary code data
15H
(One byte)
ASCII code data
31H, 35H
(Two bytes)
(Four bytes)
"1" , "5"
1234H
(Two bytes)
"4""3" ,"2" ,"1" ,
31H, 32H, 33H, 34H
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