Overview Of The Melsec Communication Protocol - Mitsubishi MELSEC Q Series Reference Manual
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Also See for MELSEC Q Series:
- Programming manual (1296 pages) ,
- User manual (814 pages) ,
- Structured programming manual (268 pages)
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1 OVERVIEW
This manual provides information on the methods that are employed by external
devices to read and write data from/to the programmable controller CPU using the data
communication functions of the MELSEC communication protocol (referred to as the
MC protocol in this manual) via the serial communication modules or Ethernet interface
modules.
When applying the following program examples to the actual system, make sure to
examine the applicability and confirm that it will not cause system control problems.
Operating procedures are explained using GX Developer.
Note that some screen names and items may differ when using GX Works2.
When performing data communication using the MC protocol, please read Chapter 2.
1.1 Overview of the MELSEC Communication Protocol
The following is an overview of the MC protocol:
(1)
(2)
MELSEC
PULL
MITSUBISHI
MELSEC
PULL
MITSUBISHI
(3)
E
N
Q
H L H L
0 0 0 1 Q R 0 X 0 0 0 0 4 0
05
30
30
30
H
H
H
(Command message of the A compatible 1C frame)
1 - 1
The MC protocol is the name of a communication method for Q/L series
programmable controller and is used by external devices to read and write device
data and programs of the programmable controller CPU via the C24 or E71.
Communications through the MC protocol can be performed if a device can
incorporate application programs and send/receive data using the control
procedures of the MC protocol.
The message formats and control procedures for an external device to access the
programmable controller CPU are defined separately for the C24 and E71.
QJ71C24
QJ71E71
Q25HCPU
S
RUN
PRM
T
RUN
ERR.
POWER
MO DE
D LINK
MODE
N
SD
RD
O
CH1.
CH2.
INIT.
COM.ERR
ERR.
RUN
OPEN
x 10 0 1 0 1
SD
RD
ERR.
CH1.
10BASE-T
USER
BAT.
BOOT
RS-232
CH.2
10BASE
SDA
1
IN
SG
2
USB
SDB
(FG)
3
RDA
4
O U T
(FG)
5
RS-232
RDB
+12V
6
RS-422
12G
7
/485
QJ71C24
QJ71E71
Q25HCPU
S
RUN
PRM
RUN
ERR.
T
MO DE
D LINK
POWER
MODE
N
O
SD
RD
CH1.
CH2.
INIT.
COM.ERR
ERR.
OPEN
RUN
x 10 0 1 0 1
SD
RD
ERR.
CH1.
10BASE-T
USER
BAT.
BOOT
RS-232
CH.2
10BASE
SDA
1
IN
SG
SDB
2
USB
(FG)
3
RDA
4
O U T
(FG)
5
RS-232
RDB
+12V
6
RS-422
12G
7
/485
The message formats and control procedures during data communication using
the MC protocol are the same as when accessing the programmable controller
CPU via conventional A/QnA series modules.
Number of
device points
2 characters
Head device
(hexadecimal)
H
L
0
2
31
51
52
30
58
30
30
30
30
34
30
30
32
H
H
H
H
H
H
H
H
H
H
H
H
H
H
QJ71C24
MELSEC
Q25HCPU
S
RUN
PRM
T
MO DE
D LINK
POWER
MODE
N
O
SD
RD
CH1.
ERR.
RUN
x 10 0 1 0 1
ERR.
USER
BAT.
BOOT
RS-232
CH.2
SDA
IN
SG
PULL
SDB
USB
(FG)
RDA
O U T
(FG)
RS-232
RDB
MITSUBISHI
RS-422
/485
S
Data for the number
Sum
of device points
check
T
code
Number of
X
device points
X 4 characters
H
L
H L H L
7
2
0 0 0 1 1 2 3 4
A
37
32
02
30
30
30
31
31
32
33
34
41
42
H
H
H
H
H
H
H
H
H
H
H
H
(Response message of the A compatible 1C frame)
1 OVERVIEW
QJ71E71
RUN
ERR.
CH2.
INIT.
COM.ERR
OPEN
SD
RD
CH1.
10BASE-T
10BASE
1
2
3
4
5
+12V
6
12G
7
E
Sum
check
T
code
X
H
L
B C D
9
8
43
44
03
39
38
H
H
H
H
H
H
1 - 1
1
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