Chapter 7. Programming SRTP Channel Commands
116 PACSystems* RX7i & RX3i TCP/IP Ethernet Communications User Manual GFK-2224Q
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 Command Block
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 ten
times, once every 7 seconds, with a timeout of 500ms for each read.
Length of Channel command Data Block (17–25 words)
Always 0 (no-wait mode request)
Memory type of COMMREQ status word (%R)
COMMREQ status word address minus 1 (%R10)
Establish Read Channel command number
The term local PLC
is used here to
identify the client
PLC—the PLC that
initiates the
communications
Number of read repetitions (read 10 times)
Time unit for read period (3=seconds)
Number of time units for read period (every 7 seconds)
Timeout for each read (500ms)
Local PLC - Memory type at which to store data (%R)
Word 14 00100 (0064)
Local PLC - Starting address at which to store data
(%R100)
The term remote
PLC is used here to
identify the server
PLC—the PLC that
responds to the
communications
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
(%R50)
Remote PLC - Number of memory units (8 registers)
Remote PLC - Network Address type (IP Address)
Remote PLC - Network Address length in words (4)
Remote PLC - Register 1 of IP address (10)
Remote PLC - Register 2 of IP address (0)
Remote PLC - Register 3 of IP address (0)
Remote PLC - Register 4 of IP address (1)
Remote PLC - Program Name (needed for access to
remote %P or %L) (zero-terminated and padded)
Remote PLC - Program Block (needed for access to
remote %L) (zero-terminated and padded)
(Word 7) Channel Command Number: Word 7 requests that a read channel be set up. If the command is
processed successfully, it will result in attempting the specified number of transfers from the server to the
client.
(Word 8) Channel Number: Word 8 specifies the channel to be used for the read. This value must be in the
range of 1–32. If the channel number is out of range, a command error indication will be placed in the
COMMREQ Status word. If the channel number is the same as a channel already in use, the channel will be re-
tasked to perform this new command.
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