Read/Write Multiple Registers (Command Code: 0X17) - Mitsubishi FX3U Series User Manual

FX Series Programmable Controllers
3U
User's Manual - MODBUS Serial Communication Edition
7.18

Read/Write Multiple Registers (Command Code: 0x17)

Reads from and writes to multiple holding registers.
Writing is executed first and reading is then executed.
1) Request message format (Master → Slave)
Function
code
Function
Read head holding
code
register number
(17 )
H
(0000 to FFFF
H H
(H) (L)
*1. The number of the specified write points must be matched with the number of bytes.
2) Response message format (Slave → Master)
(When completed normally)
Function code
Function
code
(17 )
H
(When completed with an error)
*2. Exception and error codes are stored in special data registers and special auxiliary relays in the case
of error completion. Refer to Chapter 6 for storage location, confirmation methods, and other detailed
contents.
Read points Write head holding
n register number
(0001 to 007D ) (0000 to FFFF
)
H H H
(H) (L) (H) (L)
Number of
Read
bytes
device data
n x 2 1
(H)
Function code
Function code
(97
7.18 Read/Write Multiple Registers (Command Code: 0x17)
Data
Number of
Write points
bytes
*1
m
*1
m x 2
)
(0001 to 0079 )
H H H
(0002
H
to 00F2 )
H
(H)
(L)
Data
. . .
(L) (H)
(Number of bytes n x 2)
Data
Exception
)
code * 2
H
7 MODBUS Standard Commands
Write Write
. . .
device data device data
1 m
(H) (L) (H)
(Number of bytes m x 2)
Read
device data
n
(L)
1
2
3
(L)
4
5
6
7
8
9
10
77