Read Holding Registers (Fc: 03H) - Mitsubishi Electric MELSEC iQ-R Series Reference Manual

3.3

Read Holding Registers (FC: 03H)

Operation description
Reads one or multiple holding register values.
Request message format (from master to slave)
Function code
Start holding register number
specification
03H
(H)
Response message format (from slave to master)
■ When completed successfully
Function code
Number of read
bytes n×2
03H
• For example, when n = 4, the number of read bytes is 4  2 = 8.
■ When completed with an error
Function code Data
Exception code
83H
3 MODBUS STANDARD FUNCTION DETAILS
16
3.3 Read Holding Registers (FC: 03H)
Data
(0000H to FFFFH)
(L)
Device data 1
(H) (L)
Number of read points
(0001H to 007DH)
(H) (L)
Data
Device data n
(H)
Number of read bytes n×2
(L)