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

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Establish Read Channel (2003)

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

Example 1 Command Block–Basic Example

Establish a channel (Channel 5) to a remote PLC at IP address 10.0.0.1. Return the COMMREQ Status word to %R10. Read remote PLC registers %R50–%R57 to local PLC registers %R100– %R107. Repeat the read 10 times, once every 7 seconds, with a timeout of 500 ms for each read.

		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	02003	(07D3)	Establish Read Channel command number
	Word 8	00005	(0005)	Channel number (5)
	Word 9	00010	(000A)	Number of read repetitions (read 10 times)
The term local PLC is	Word 10	00003	(0003)	Time unit for read period (3=seconds)
	Word 11	00007	(0007)	Number of time units for read period (every 7 seconds)
used here to identify the	Word 12	00050	(0032)	Timeout for each read (500 ms)
client PLC—the PLC	Word 13	00008	(0008)	Local PLC - Memory type at which to store data (%R)
that initiates the	Word 14	00100	(0064)	Local PLC - Starting address at which to store data
communications				(%R100)
request.
	Word 15	00008	(0008)	Remote PLC - Memory type from which to read data (%R)
	Word 16	00050	(0032)	Remote PLC - Starting address from which to read data
The term remote PLC is				(%R50)
used here to identify the	Word 17	00008	(0008)	Remote PLC - Number of memory units (8 registers)
server PLC—the PLC	Word 18	00001	(0001)	Remote PLC - Network Address type (IP Address)
that responds to the	Word 19	00004	(0004)	Remote PLC - Network Address length in words (4)
communications	Word 20	00010	(000A)	Remote PLC - Register 1 of IP address (10)
request.	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.

3-10 TCP/IP Ethernet Communications for the Series 90™ PLC User's Manual– May 2002 GFK-1541B