Read/Write Multiple Registers To/From A Modbus Server Device (3005) - GE RX3i User Manual

Read/Write Multiple Registers to/from a Modbus Server Device
(3005)
The Read/Write Multiple Registers to/from a Modbus Server Device COMMREQ is used to read and write data
between the remote server and the PLC with one COMMREQ operation. Note, the write operation occurs first
and the data exchange does not occur coherently (i.e. data can change in the server between the write and
read operations).
Command 3005, Example – Read/Write Multiple Register
Write 10 values starting at %R100 in the Local PLC to register address 200 in the remote Modbus/TCP server
and read 20 values starting from register 300 in the remote Modbus/TCP server and write this value to %R300
in the Local PLC. Return the COMMREQ Status word to %R10. Use channel 6, a channel previously opened with
the Open Modbus/TCP Client Connection COMMREQ.
Dec (Hex)
Word 1 00014 (000E)
Word 2 00000 (0000)
Word 3 00008 (0008)
Word 4 00009 (0009)
13
Word 5 00000 (0000)
Word 6 00000 (0000)
Word 7 03005 (0BBD)
Word 8 00006 (0006)
Word 9 00023 (0017)
Word 10 00008 (0008)
Word 11 00300 (012C)
Word 12 00000 (0000)
Word 13 00300 (012C)
Word 14 00020 (0014)
Word 15 00008 (0008)
Word 16 00100 (0064)
Word 17 00000 (0000)
Word 18 00200 (00C8)
Word 19 00010 (000A)
Word 20 00001 (0001)
(Word 7) Channel Command Number: Word 7 identifies the COMMREQ as a Read/Write Multiple Register
operation on remote Modbus/TCP device.
(Word 8) Channel Number: Word 8 identifies the channel number previously allocated for communication with
the remote Modbus/TCP server.
GFK-2224Q
Length of Channel command Data Block
Always 0 (no-wait mode request)
Memory type of CRS word (%R)
CRS word address minus 1 (%R10)
Reserved
Reserved
Read/Write Multiple Registers to/from a Modbus/TCP Device
Channel number (6)
Modbus Function Code – Read/Write Multiple Registers
Local PLC Memory Type of memory to write with data read from Remote Device
Local PLC Starting Address (LSW) of memory to write with data read from Remote
Device
Local PLC Starting Address (MSW) of memory to write with data read from
Remote Device (normally 0 unless %W is used)
Address to Read From on Remote Server
Number of Memory Units to Read from Remote Device (1 to 125)
Local PLC Memory Type of memory to use for writing to the Remote Device
Local PLC Starting Address (LSW) of memory to use for writing to the Remote
Device
Local PLC Starting Address (MSW) of memory to use for writing to the Remote
Device (normally 0 unless %W is used)
Address to Write to on the Remote Server
Number of Memory Units to Write to the Remote Device (1 to 121)
Unit Identifier
January 2017
Chapter 9. Modbus/TCP Client
159