Mitsubishi QJ71MT91 User Manual

4 - 20 4 - 20
MELSEC-Q
4 MODBUS
R
STANDARD FUNCTIONS
4.3.12 Read/Write multiple registers (FC:23)
Reads and writes data from and to multiple holding registers.
Write is executed first and read is then executed.
Number of accessible devices with one message
Read: 1 to 125 points
Write: 1 to 121 points
(1) Request message format (Master Slave)
Data
Read head holding
register number
(0000
H
to FFFF
H
)
(H) (L)
Function code
Function code
(17
H
)
Read points
n
(0001
H
to 007D
H
)
(H) (L) (H) (L)
Write head holding
register number
(0000
H
to FFFF
H
)
(Number of bytes m 2)
Write points
m*1
(0001
H
to 0079
H
)
(H) (L) (H) (L)
Number
of bytes
m 2*1
(0000
H
to 00F2
H
)
Write device data
1
(H) (L)
Write device data
m
1: The number of points specified as the write points must be matched with the
number of bytes.
(2) Response message format (Slave Master)
(When completed normally)
Read device data
1
Data
(H) (L)
Function code
Function code
(17
H
)
(H) (L)
Number of bytes
n 2
Read device data
n
(Number of bytes n 2)
(When completed with an error)
Data
Exception
code *2
Function code
Function code
(97
H
)
2: When completed with an error, the exception code and error code are stored
into the buffer memory.
Refer to Section 11.3 for the storage location, confirmation method and more
details.

Mitsubishi QJ71MT91 Specifications

General

Brand	Mitsubishi
Model	QJ71MT91
Category	Controller
Language	English