Spectrum Controls 1756sc-IF8u - Manual (Page 39)

Chapter 3: Operation within the System
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When the controllers begin downloading configuration data, both try to
establish a connection with the input module. Whichever controller’s data
arrives first establishes a connection. When the second controller’s data
arrives, the module compares it to its current configuration data (the data
received and accepted from the first controller).
If the configuration data sent by the second controller matches the
configuration data sent by the first controller the connection is also
accepted. If any parameter of the second configuration data is different
from the first, the module rejects the connection and the user is informed
by an error in the software.
The advantage of multiple owners over a ‘Listen-only’ connection is that
now either of the controllers can lose the connection to the module and
the module will continue to operate and multicast data to the system
because of the connection maintained by the other owner controller.
Note: The previous discussion of multiple owners assues the
configuration tag “.configrevnumber” is set to 1. Operation differs is the
tag is set to 0. Refer to Chapter 5 for descriptions of this tag’s settings.
Configuration
Changes in an
Input Module with
Multiple Owners
You must be careful when changing an input module’s configuration data
in a multiple owner scenario. When the configuration data is changed in
one of the owners, for example, Controller A, and sent to the module,
that configuration data is accepted as the new configuration for the
module. Controller B will continue to listen, unaware that any changes
have been made in the module’s behavior.
Important: When changing configuration for a module with multiple
owners, we recommend the connection be inhibited. To prevent other
owners from receiving potentially erroneous data, as described above,
the following steps must be followed when changing a module’s
configuration in a multiple owner scenario when online:
1. For each owner controller, inhibit the controller’s connection to the
module in the software on the I/O Module Connection tab.
2. Make the appropriate configuration data changes in the software.
3. Repeat steps 1 and 2 for all owner controllers, making the exact
same changes in all controllers.
4. Uncheck the Inhibit box in each owner’s configuration to reconnect
each module.