Rockwell Automation T3831 ICS Regent Communications Package for Winterpret - Manual (Page 4)

Communications Package for W INTERPRET (T3831)
4
Industrial Control Services
Theory of Operation
Each leg of the GPL network uses a bussed multidrop RS-485
communication link for exchanging data between up to 31
Regents. When loaded and operating, the GPL
communications activity on each leg sequences through
polling commands and broadcast responses as shown in
Figure 2. The completion of this sequence for each Regent on
the network makes up a GPL communications cycle. This
cycle repeats continuously while the GPL master for the leg is
operating. Each leg of the network runs asynchronous to each
other.
Figure 2. The GPL communications cycle.
During the communications cycle the GPL master issues a
poll command to a Regent to transmit its GPL data packet.
The polled Regent broadcasts its GPL data packet which
contains all of the GPL variables configured for the Regent.
Each Regent on the network receives the broadcasted GPL
data packet and stores the contents in an internal GPL input
buffer. The GPL master then issues a poll command to the
next Regent on the network to transmit its GPL data packet.
This sequence continues until all Regents identified in the
GPL configuration have been polled and subsequently
broadcast their GPL data packets. The GPL master repeats
the communication cycle continuously.
Internal to each Regent configured for GPL communications
are input templates, output templates, input data buffers and
output data buffers. Each of these are described below.
Input Templates
The Regent has an input template for every configured node
on the network (including itself). Figure 3 illustrates the
structure of the GPL input templates for each Regent
configured for Guarded Peer-Link communications.