GE GFK-1541B manual Establish Write Channel, Example 1 Command Block-Basic Example

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Establish Write Channel (2004)

The Establish Write Channel command requests that a channel be connected to a remote PLC and that data from the local PLC be transferred (periodically) to the remote PLC. The Command Block specifies the period, the number of writes to the server (remote PLC) to perform, and the timeout allowed in waiting for each transfer to complete. The first write is performed immediately, regardless of the period specified.

Example 1 Command Block–Basic Example

Establish a write channel (Channel 6) to a remote PLC at IP address 10.0.0.1. Return the COMMREQ Status word to %R10. Write local PLC registers %R50–%R57 to remote PLC registers %R100–%R107. Repeat the write indefinitely, once every 7 seconds, with a timeout of 500 ms for each write.

The term local PLC is used here to identify the client PLC—the PLC that initiates the communications request.

The term remote PLC is used here to identify the server PLC—the PLC that responds to the communications request.

	Dec	(Hex)
Word 1	00017	(0011)	Length of Channel command Data Block (17–25 words)
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	02004	(07D4)	Establish Write Channel command number
Word 8	00006	(0006)	Channel number (6)
Word 9	00000	(0000)	Number of write repetitions (write indefinitely)
Word 10	00003	(0003)	Time unit for write period (3=seconds)
Word 11	00007	(0007)	Number of time units for write period (every 7 seconds)
Word 12	00050	(0032)	Timeout for each write (500 ms)
Word 13	00008	(0008)	Local PLC - Memory type from which to write data (%R)
Word 14	00050	(0032)	Local PLC - Starting address from which to write data (%R50)
Word 15	00008	(0008)	Remote PLC - Memory type at which to store data (%R)
Word 16	00100	(0064)	Remote PLC - Starting address at which to store data
			(%R100)
Word 17	00008	(0008)	Remote PLC - Number of memory units (8 registers)
Word 18	00001	(0001)	Remote PLC - Network Address type (IP address)
Word 19	00004	(0004)	Remote PLC - Network Address length in words (4)
Word 20	00010	(000A)	Remote PLC - Register 1 of IP address (10)
Word 21	00000	(0000)	Remote PLC - Register 2 of IP address (0)
Word 22	00000	(0000)	Remote PLC - Register 3 of IP address (0)
Word 23	00001	(0001)	Remote PLC - Register 4 of IP address (1)
Word 24–27			Remote PLC - Program Name (needed for access to remote
			%P or %L) (zero-terminated and padded)
Word 28–31			Remote PLC - Program Block (needed for access to remote
			%L) (zero-terminated and padded)

*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 requests that a write channel be set up. If the command is processed successfully, it will result in attempting the specified number of transfers from the client to the server.

(Word 8) Channel Number: Word 8 specifies the channel to be used for the write. This value must be in the range of 1–32 for Series 90-70 PLCs and 1–16 for Series 90-30 PLCs. If the channel number is out of range, a command error indication will be placed in the COMMREQ

GFK-1541B Chapter 3 Programming Channel Commands 3-17