GE PACSystems RXi User Manual page 183

Chapter 8. Gigabit Ethernet (GbE) Interface Overview and Operation
Data returned from the remote device is stored in the controller data area specified in the
Read Modbus TCP Device COMMREQ. Data can be stored in any of the controller data
areas. Refer to page 171 for the list of data areas and identification codes for the controller.
Note that the first item referred to in each data area is item 1 not item 0.
The COMMREQ Status Word (CRS) indicates the success or failure of the Read Data
COMMREQ. If the COMMREQ requests an invalid channel number or any other field is
invalid the COMMREQ fails and the CRS is set to a non-zero value to identify the failure.
Refer to Status Data on page 152 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.
Word 1
Word 2
Word 3
Word 4
Word 5
Word 6
Word 7
Word 8
Word 9
Word 10
Word 11
Word 12
Word 13
Word 14
(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.
170
Dec (Hex)
00008 (0008) Length of Channel command Data Block
00000 (0000) Always 0 (no-wait mode request)
00008 (0008) Memory type of CRS word (%R)
00009 (0009) CRS word address minus 1 (%R10)
00000 (0000) Reserved
00000 (0000) Reserved
03003 (0BBB) Read from a Modbus TCP Device
00006 (0006) Channel number (6)
00004 (0004) Modbus Function Code (Read Input Registers)
00008 (0008) Local Controller Memory Type
00020 (0014) Local Controller Starting Address
00200 (00C8) Address in the Remote Server
00004 (0004) Number of Registers in the Remote Device
00001 (0001) Unit Identifier
PACSystems* RXi Distributed IO Controller User Manual
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GFK-2816F