Installation guide

26 Introducing the Modbus Plus Network
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Receiving Data
Nodes can be configured to receive two kinds of Peer Cop data:
V Global Input Up to 32 words of global data can be received by
each node from each other node on the network. Destination
references are specified in the receiving node’s configuration. Up to
eight blocks of references can be specified, giving up to eight
separate destinations for the data received from each source node.
The incoming data can be indexed to establish the starting point
and length of each block of data to be extracted from the message
and delivered to each destination.
V Specific Input Up to 32 words of data can be received from any
specific node. Each node on the network can be specifically defined
as a data source, up to the maximum of 500 data words.
The net effect of using Peer Cop for data transactions is that each
sending node can specify unique references as data sources, and each
receiving node can specify the same or different references as data
destinations. When receiving global data, each node can index to
specific locations in the incoming data and extract specific lengths of
data from those points. Data is thus transacted rapidly as part of each
token pass, and can be directly mapped between data references in the
sending and receiving nodes.
Applications can be designed in which alarms and setpoints are
transmitted (globally), with required actions by specific nodes also
defined (specifically). Because all nodes detect the token passes, Peer
Cop global data can be rapidly known to all nodes, with each node’s
specific data requirements also rapidly known to just that node.
Because Peer Cop data is transacted as part of the token pass, it
applies to each network independently of any other networks that are
part of the Modbus Plus system. Tokens are not exchanged between
networks, because they are not passed through Bridge Plus devices.
Each network maintains its own Peer Cop database, with its own
system of global broadcasting and specific node addressing.