GE PACSystems RXi User Manual page 190

Command 3004, Example 2 – Write Single Coil
Set coil 501 ON in the remote Modbus TCP device using the value at %Q4. Return the
COMMREQ Status word to %R10. Use channel 6, a channel previously opened with the
Open Modbus TCP Client Connection COMMREQ.
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 Write Data to
Modbus TCP device.
(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 5 Write Single Coil.
(Word 10) Local Controller Memory Type: Words 10–11 specify the location in the local controller
from where the Ethernet interface will get the data to be written to the remote controller. Valid
values for Word 10 are listed on page 171.ICRXICTL000, GFK-2816, GFK2816
(Word 11) Local Controller Starting Address: Word 11 determines the starting address in the local
controller from which the data is to be written. The value entered is the offset (1-based) from
the beginning of controller memory for the memory type and mode specified in Word 10. This
offset will be either in bits, bytes, or words depending on the mode specified. Valid ranges of
values depend on the controller's memory ranges.
(Word 12) Remote Device Address: Word 12 specifies the destination coil address in the Modbus
TCP device.
(Word 13). Number Coils in Remote Device: Words 13 specifies the quantity of coils to write to the
remote device. For Modbus Function Code 5, Write Single Coil, this must be set to 1.
(Word 14) Unit Identifier: This field is typically used by Ethernet to Serial bridges to specify the
address of a Modbus Slave on a multi-drop link. The Modbus TCP Unit Identifier is a special
control code used in a Modbus TCP message block.
GFK-2816F
Chapter 8. Gigabit Ethernet (GbE) Interface Overview and Operation
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
03004 (0BBC) Write to a Modbus TCP Device
00006 (0006) Channel number (6)
Modbus Function Code – Write Single Coil
00005 (0005)
00072 (0048) Local Controller Memory Type
00004 (0004) Local Controller Starting Address
00501 (01F5) Address in the Remote Device
00001 (0001) Number of Coils in the Remote Device.
00001 (0001) Unit Identifier
August 2015
6
177