IBM Modbus Plus Computer Drive User Manual


 
Modbus Plus X-Link Driver User’s Guide
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4.3 Destination Accesses
The Modbus Plus driver supports three possible destination accesses.
The first destination defines a local address which allows any device on the
Modbus Plus network to read the data from the X-Link. This type of
destination can be used to allow a PLC to read back the data it has written.
Programming must be provided on the remote device to initiate the read.
The second type of destination access supported by the Modbus Plus driver
is an X-Link initiated write. This destination defines an external address
which the X-Link uses to write the data to a remote node on the network.
This access also requires the user to specify when to write the data. This type
of data destination does not require any programming in the remote node and
can avoid wasting network bandwidth that would be consumed by having the
PLC poll the data.
The last type of destination access supported is global data. The X-Link
writes the values into the global data table for the Modbus Plus station that is
X-Link.