Read Holding Registers (Command Code: 0X03) - Mitsubishi FX3U Series User Manual

FX Series Programmable Controllers
3U
User's Manual - MODBUS Serial Communication Edition
7.6

Read Holding Registers (Command Code: 0x03)

Reads the values of one or more holding registers.
1) Request message format (Master → Slave)
2) Response message format (Slave → Master)
(When completed normally)
Function code
Function
code
(03
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.
52
Function code
Function Head holding register
number
code
(0000
(03 )
H
(H)
Number of Device data
read bytes
*1
) m = n x 2
(H)
Function code
Function
code
(83
7.6 Read Holding Registers (Command Code: 0x03)
Data
Read points
(0001
to FFFF )
H H
(L) (H)
Data
. . .
1
(L)
(Number of read bytes n x 2)
*1 For example, if n = 4, the number of bytes is
calculated as 4 x 2 = 8 bytes
Data
Exception
code *
2
)
H
7 MODBUS Standard Commands
to 007D )
H H
(L)
Device data
n
(H)
(L)