SEW-Eurodrive MOVIPRO Ethernet/IP - Service FC23 - Read;Write Multiple Registers

9
Modbus protocol (Modbus/TCP)
Protocol structure
Manual – MOVIPRO
®
with EtherNet/IP™ or Modbus/TCP Fieldbus Interface
106
9.2.4 Service FC23 – Read/write multiple registers
With the service "FC23 – Read/write multiple registers", you can simultaneously write
and read a variable number of registers. The write access is carried out first. Prefer-
ably, this service is used for the process data.
MBAP Header Function Code Data (FC23)
Bytes
(1 – N)
FC
Read Address Write Address
Write Data
Read Word Count
Write Word Count
(1+10+N)
Transaction ID Length
(0x00)
Protocol ID
(0x00)
Unit ID
(N)
(0x17)
9007200887389707
Example
Request:
Byte Designation Meaning/permitted values
0–6 MBAP header See chapter "Header"(→2103)
7 Function code
Requested service
Value: 23 (Read/Write Multiple Registers)
8 Read reference number (high) Value: Offset
9 Read reference number (low) Value: Offset
10 Read word count (high)
Number of words (register) that are read.
Value: always 0
11 Read word count (low) Number of words (register) that are read.
12 Write reference number (high) Value: Offset
13 Write reference number (low) Value: Offset
14 Write word count (high)
Number of words (register) that are written.
Value: always 0
15 Write word count (low) Number of words (register) that are written.
16 Write byte count
Number of following bytes
Value: 2 x N
1)
17–17+(2 x
N)
1)
Write register values
Value that is written in the respective register
Value: 2–2 x N data bytes depending on length
1) Number of registers that are written.
Response:
Byte Designation Meaning/permitted values
0–6 MBAP header See chapter "Header"(→2103)
7 Function code
Service
Value: 23 (Read/Write Multiple Registers)
8 Byte count
Number of following bytes
Value: 2 x n
1)
9 Data
Content of the respective register
Value: 2–2 x n data bytes depending on length
1) Number of registers that are read.
Exception:
Byte Designation Meaning/permitted values
0–6 MBAP header See chapter "Header"(→2103)
7 Function code 97
hex
8 Exception Code Error code
16998413/EN – 12/2016