Connecting with MC Protocol Communication (MITSUBISHI MELSEC PLCs)
How to Connect with 3E Frames in Binary Code

Overview

Among the protocols of the MC protocol communication function available on the Ethernet port of MITSUBISHI MELSEC PLCs, this explains communication with 3E frames in binary code.
When a MELSEC PLC receives an MC protocol command, it returns the data corresponding to the command, so no ladder program is needed.
MC protocol communication over the Ethernet port can use both TCP/IP and UDP/IP.

What Is the MC Protocol?

A protocol used in serial and Ethernet communication in which a PC or host device sends MC protocol commands to a MELSEC PLC to read and write devices (relays and data memory), change modes and more, without a ladder program on the PLC.

Types of Frames (Messages)

The MC protocol access range when connected from an external device via Ethernet is as follows

Types of MC protocol Ethernet frames
Frame	Characteristics	Compatible messages	Supported codes
4E	3E frame + "serial number"	SLMP messages	ASCII/BIN
3E	For QnA series Ethernet units	SLMP messages QnA series Ethernet unit messages	ASCII/BIN
1E	For A series Ethernet units	A series Ethernet unit messages	ASCII/BIN

[Reference] Frames when connected via serial communication
Frame	Characteristics	Compatible messages	Model
4C	Maximum access range	For QnA series serial communication units only (QnA extended frame)	1～5
3C	For QnA series data communication	For QnA series serial communication units only	1～4
2C	For QnA series data communication	For A series serial communication units only	1～4
1C	For A series data communication	For A series computer link units only	1～4

[Reference] Formats when connected via serial communication
Model	Code	Remarks
Format 1	ASCII
Format 2	ASCII	Block number added
Format 3	ASCII	Format enclosed in STX and ETX
Format 4	ASCII	CR LF added at the end
Format 5	BIN	Usable with 4C frames only

3E Frame Binary Code Messages

Excluding the Ethernet TCP/UDP header

Request message

Example of reading the value of DM10 of the connected station (own station)
Subheader		Access route					Request data length		Monitoring timer		Request data
		Network number	PC number	Request destination module I/O number		Request destination module station number					Command
											Read		Subcommand		First device				Number of points
50	00	00	FF	FF	03	00	0C	00	08	00	01	04	00	00	0A	00	00	A8	01	00

Request data length: number of bytes from the monitoring timer to the end of the request data: 000C (12 bytes)
Monitoring timer: 0.25 s × setting (0001H to 0028H recommended): 0008 = 0.25 × 8 = 2 s
Read command: 0401
Subcommand: 0000
First device: A800000A: A8 = DM, 00000A = 10
Number of points: 0001: 1

Response message

Subheader		Access route					Response data length		End code		Response data
		Network number	PC number	Request destination module I/O number		Request destination module station number
D0	00	00	FF	FF	03	00	04	00	00	00	34	12

Response data length: number of bytes from the end code to the end of the response data: 0004 (4 bytes)
End code: 0000
Response data: 1234 (hexadecimal)

Command list

Command List for 4C/3C/4E/3E Frames
Command	Functions
0401	Batch read
1401	Batch write
0403	Random read
1402	Random write
0406	Multiple block batch read
1406	Multiple block batch write
0801	Register monitor data
0802	Monitor
041A	Batch read of array labels (iQ-R series only)
141A	Batch write of array labels (iQ-R series only)
041C	Random read of labels (iQ-R series only)
141B	Random write of labels (iQ-R series only)
0613	Buffer memory batch read
1613	Buffer memory batch write
0601	Intelligent function module batch read
1601	Intelligent function module batch write
1001	Remote RUN
1002	Remote STOP
1003	Remote PAUSE
1005	Remote latch clear
1006	Remote RESET
0101	Read CPU model name
1630	Remote password unlock
1631	Remote password lock
0619	Loopback test
1617	Clear error information
1810	Read directory/file information
1811	Search directory/file information
1820	Create new file
1822	Delete file
1824	Copy file
1825	Change file attributes
1826	Change file creation date/time
1827	Open file
1828	Read file
1829	Write to file
182A	Close file
0601	Serial communication only: read registered data
1610	Serial communication only: register data
1618	Serial communication only: global signal control
1615	Serial communication only: initialize transmission sequence
1612	Serial communication only: mode switching
0630	Serial communication only: register PLC CPU monitoring
0631	Serial communication only: deregister PLC CPU monitoring
2101	On-demand

Device Code List

Device symbol	Device code
	Q/L series	iQ-R series
SM	91	0091
SD	A9	00A9
X	9C	009C
Y	9D	009D
M	90	0090
L	92	0092
F	93	0093
V	94	0094
B	A0	00A0
D	A8	00A8
W	B4	00B4
TS	C1	00C1
TC	C0	00C0
TN	C2	00C2
LTS		0051
LTC		0050
LTN		0052
STS	C7	00C7
STC	C6	00C6
STN	C8	00C8
LSTS		0059
LSTC		0058
LSTN		005A
CS	C4	00C4
CC	C3	00C3
CN	C5	00C5
LCS		0055
LCC		0054
LCN		0056
SB	A1	00A1
SW	B5	00B5
S	98	0098
DX	A2	00A2
DY	A3	00A3
Z	CC	00CC
LZ		0062
R	AF	00AF
ZR	B0	00B0

Command Explanations (Partial)

0401

Batch read

Reads consecutive devices in batch with the number of device points specified

● Reading bit devices in word units

Read 1 word from M100
Command		Subcommand		First device				Number of points
01	04	00	00	64	00	00	90	01	00

Response data
Response data
34								12
0	0	1	1	0	1	0	0	0	0	1	0	0	1	0
M107				M100				M115				M108

● Reading word devices in word units

Read 3 words from D100
Command		Subcommand		First device				Number of points
01	04	00	00	64	00	00	A8	03	00

Response data
Response data
34	12	78	56	BC	9A
D100		D101		D102

● Reading in bit units

Read 8 bits from M100
Command		Subcommand		First device				Number of points
01	04	01	00	64	00	00	90	08	00

Response data
Response data
00	10	11	00
M100		M107

1401

Batch write

Writes values to devices in word units

● Writing bit devices in word units

Write 1 word from M100
Command		Subcommand		First device				Number of points		Write data
01	14	00	00	64	00	00	90	01	00	34								12
										0	0	1	1	0	1	0	0	0	0	0	1	0	0	1	0
										M107				M100				M115				M108

There is no response data

● Writing word devices in word units

Write 3 words from D100
Command		Subcommand		First device				Number of points		Write data
01	14	00	00	64	00	00	A8	03	00	34	12	78	56	BC	9A
										D100		D101		D102

There is no response data

● Writing in bit units

Write 8 bits from M100
Command		Subcommand		First device				Number of points		Write data
01	14	01	00	64	00	00	90	08	00	00	11	01	00
										M100		M107

There is no response data

0403

Random read

Reads values by specifying non-consecutive device numbers

● Reading in word units

Word read of D0 and M100 and double word read of D100
Command		Subcommand		Number of word points	Number of double word points	Word device number 1				Word device number 2				Double word device number 1
03	04	00	00	02	01	00	00	00	A8	64	00	00	90	64	00	00	A8

Response data
Response data
34	12	01	00	34	12	78	56
D0		M100		D100		D101

0801

Register monitor data

Registers the devices to monitor

● No monitoring condition specified

Word read of D0 and M100 and double word read of D100
Command		Subcommand		Number of word points	Number of double word points	Word device number 1				Word device number 2				Double word device number 1
01	08	00	00	02	01	00	00	00	A8	64	00	00	90	64	00	00	A8

There is no response data

0802

Register monitor data

Reads the values of the registered devices

Command		Subcommand
02	08	00	00

Response data
Response data
34	12	01	00	34	12	78	56
D0		M100		D100		D101

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Connecting with MC Protocol Communication (MITSUBISHI MELSEC PLCs)
How to Connect with 3E Frames in Binary Code

Overview

What Is the MC Protocol?

Types of Frames (Messages)