Allen-Bradley 1404-M4, User Manual

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Publication 1404-UM001D-EN-E - October 2004
6-4 I/O Operations
Communications Loss Behavior
The Default output state on communications loss defines the behavior
of the output if the Powermonitor 3000 experiences a loss of
communications. What constitutes a communications loss depends on
the protocol. A Remote I/O unit declares a communications loss if it
has detected more than 100 mSec between valid frames or more than
255 consecutive valid frames not addressed to it. A DeviceNet unit
declares a communications loss when the network master (scanner)
has not polled it within the Expected Packet Rate that you configured
when setting up the I/O connection.
You may select one of the following behaviors for each output:
•
Last-state / resume : holds the output in its last state during a
communications loss and resume the output control when
communication recovers.
•
Last-state / freeze: holds the output in its last state during a
communications loss and freezes the output in this state when
communication recovers. You may clear the freeze by placing
the logic controller into program mode, changing the behavior
to last state / resume, or cycling power to the Powermonitor
3000.
•
De-energize / resume : de-energizes the output during
communications loss and resume output control when
communication recovers.
•
De-energize / freeze: de-energizes the output during
communications loss and freezes the output de-energized when
communication recovers. You may clear the freeze by placing
the logic controller into program mode, changing the behavior
to last state / resume, or cycling power to the Powermonitor
3000.
IMPORTANT
The relay output contacts and solid-state KYZ output
contacts on the Powermonitor 3000 may be used to
control other devices through setpoint control or
communications, The response of these outputs to a
communications failure is configurable by the user.
Be sure to evaluate the safety impact of the output
configuration on your plant or process.