Chapter 7. Programming SRTP Channel Commands
120 PACSystems* RX7i & RX3i TCP/IP Ethernet Communications User Manual GFK-2224Q
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 Command Block
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 500ms for each write.
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 Write Channel command number
PLC is used here
to identify the
client PLC—the
PLC that initiates
the
communications
Number of write repetitions (write indefinitely)
Time unit for write period (3=seconds)
Number of time units for write period (every 7 seconds)
Timeout for each write (500ms)
Local PLC - Memory type from which to write data (%R)
Word 14 00050 (0032)
Local PLC - Starting address from which to write data
(%R50)
The term remote
PLC is used here
to identify the
server PLC—the
PLC that responds
to the
communications
request.
Remote PLC - Memory type at which to store data (%R)
Word 16 00100 (0064)
Remote PLC - Starting address at which to store data
(%R100)
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)
Word 24–
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 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. 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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