GE GFK-1541B manual Command 3003 Example

4

Command 3003 Example 1

Read four Input Registers from Address 30200 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	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
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 4 (CRS word address) is the only zero-based address in the Command Block. Only this value requires subtracting 1 from the intended address.

(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.

4-12 TCP/IP Ethernet Communications for the Series 90™ PLC User's Manual– May 2002 GFK-1541B