Read/Write Multiple Registers (Fc: 23) - Mitsubishi QJ71MB91 User Manual

4
MODBUS(R) STANDARD FUNCTIONS

4.20 Read/Write Multiple Registers (FC: 23)

Reads from or writes to multiple holding registers.
Writing is executed first and reading is then executed.
(1) Request message format (Master
Function
code
Function
Read head holding
code
register number
(17 )
H
(0000 to FFFF ) (0001
H H
(H) (L)
(2) Response message format (Slave
(When completed normally)
(When completed with an error)
Function code
Figure 4.100 Read/Write multiple registers (Exception message)
Read points Write head holding
n register number
to 007D ) (0000 to FFFF )
H H H H
(L) (H) (L)
(H)
Figure 4.98 Read/Write multiple registers (Request message)
* 1 The number of the specified write points must be matched with the number of bytes.
Function code
Function Number of
code bytes
(17 ) n x 2
H
Figure 4.99 Read/Write multiple registers (Normal response message)
Function code Data
Exception
(97 )
H code * 2
* 2 Exception and error codes are stored in the buffer memory in the case of error completion.
Refer to the following for storage location, confirmation methods, and detailed contents.
Section 11.4
Slave)
Data
Write points Number of Write
bytes
device data
m *1
m x 2 *1
(0001 to 0079 )
H H
(0000
H
to 00F2 )
H
(H)
(L) (H)
Master)
Data
Read
. . .
device data
1
(H) (L)
(Number of bytes n x 2)
4.20 Read/Write Multiple Registers (FC: 23)
Write
. . .
device data
m
1
(L) (H) (L)
(Number of bytes m x 2)
Read
device data
n
(L)
(H)
4
1
2
3
4
5
6
7
8
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