Read/Write Multiple Registers (Fc: 17H) - Mitsubishi Electric MELSEC iQ-R Series Reference Manual

3.17

Read/Write Multiple Registers (FC: 17H)

Operation description
Reads/writes data from/to multiple holding register areas.
During the processing, writing is performed first, followed by reading.
Request message format (from master to slave)
Function code
Read start holding Number of read points
register number n
17H
(0000H to FFFFH) (0001H to 007DH)
(H) (L)
Ensure that the specified number of write points matches the number of bits specified with the number of
bytes.
Response message format (from slave to master)
■ When completed successfully
Function code
Number of bytes
n×2
17H
■ When completed with an error
Function code Data
Exception code
97H
Write start holding
register number
(0000H to FFFFH)
(H) (L) (H) (L)
Data
Read device data 1
(H) (L)
Number of bytes n×2
Data
Number of write points Number of Write device data 1
m bytes m×2
(00H to F2H)
(0001H to 0079H)
(H) (L) (H)
Read device data n
(H) (L)
3 MODBUS STANDARD FUNCTION DETAILS
3.17 Read/Write Multiple Registers (FC: 17H)
Write device data m
(L) (H) (L)
Number of bytes m×2
3
49