Installation guide

112 Estimating Network Performance
890 USE 100 00
3.23 Sample Communications Across Networks
Figure 44 shows two controllers on separate Modbus Plus networks
joined by a bridge. Each controller has its own peer processor. The
bridge has a separate peer processor for each network. Each network
has a separate token rotation pattern and timing.
CONTROLLER
A
PEER
PROCESSOR
CONTROLLER
B
PEER
PROCESSOR
NETWORK A NETWORK B
PEER
PROCESSOR
PEER
PROCESSOR
BRIDGE
REQUEST >
< RESPONSE
REQUEST >
< RESPONSE
Figure 44 Sample READ Communication Across Networks
During the ladder logic scan in unit A, an MSTR block is executed that
specifies a read request to unit B. At the end of the block execution, the
read request is sent to the peer processor in unit A. The following
events occur:
Step 1 When the peer processor in unit A acquires the network token, it
transmits the read request. The peer processor in the bridge sends an
immediate acknowledgement.
Step 2 When the bridge has the token on network B, it transmits the read
request to unit B. The peer processor in unit B sends an immediate
acknowledgement to the bridge.
Step 3 At the end of the ladder logic scan in unit B, the incoming
transactions are handled. The peer processor in unit B is ready with
the data response to the read request.