GE RX3i - Page 162

Chapter 9. Modbus/TCP Client
GFK-2224Q January 2017 149
zero value to identify the failure. See the section “Status Data” later in this chapter for detailed CRS failure
codes.
Command 3003, Example 1
Read four Input Registers from Input Registers in the remote Modbus/TCP device. Store the registers at location
%R20. Return the COMMREQ Status word to %R10.
Dec (Hex)
Word 1 00008 (0008) Length of Channel command Data Block
Word 2 00000 (0000) Always 0 (no-wait mode request)
Word 3 00008 (0008) Memory type of CRS word (%R)
Word 4
13
00009 (0009) CRS word address minus 1 (%R10)
Word 5 00000 (0000) Reserved
Word 6 00000 (0000) Reserved
Word 7 03003 (0BBB) Read from a Modbus/TCP Device
Word 8 00006 (0006) Channel number (6)
Word 9 00004 (0004) Modbus Function Code (Read Input Registers)
Word 10 00008 (0008) Local PLC Memory Type
Word 11 00020 (0014) Local PLC Starting Address
Word 12 00200 (00C8) Address in the Remote Server
Word 13 00004 (0004) Number of Registers in the Remote Device
Word 14 00001 (0001) Unit Identifier
(Word 7) Channel Command Number: Word 7 identifies the COMMREQ as a Read Data from Modbus/TCP
Device command block.
(Word 8) Channel Number: Word 8 identifies the channel number previously allocated for communication with
the remote Modbus/TCP server.
(Word 9) Modbus Function Code: Word 9 specifies Modbus Function Code 4, Read Input Registers.