Allen-Bradley 1756-DHRIO - Remote I;O Adapter Failure Notification

Publication 1756-UM514B-EN-P - February 2003
Using the 1756-DHRIO Module in Remote I/O Applications 8-17
Remote I/O Adapter
Failure
Notification
The speed at which the ControlLogix controller is notified that a
remote I/O adapter has faulted is directly related to the RPI. The fault,
known as a connection timeout, occurs at 4 times the RPI. For
example, if the RPI is set at 25ms and a fault occurs, the ControlLogix
controller is not notified for 100ms. For more information on
connection timeouts, see
page 2-15.
A remote I/O adapter fault notification occurs whenever the
communication between the remote I/O scanner (Channel A or B)
and a remote I/O adapter is interrupted or the communication
between the 1756-DHRIO module and the ControlLogix controller is
interrupted.
RSLogix 5000 alerts you to a rack fault in at least one of the following
ways:
· nonzero condition in the Rack Status tag in the tag editor
· fault icon appears in the controller organizer
· connections page displays the fault type
Inhibiting the 1756-DHRIO
Module Connections
When the inhibit bit is set for the 1756-DHRIO module, the
connection between the ControlLogix controller and the 1756-DHRIO
module is terminated.
Although the 1756-DHRIO module connection is inhibited, the DHRIO
scanner (Channel A or B) changes to program mode and continues to
scan the remote I/O adapters on the remote I/O network. When
inhibited, a 1756-DHRIO module accepts configuration from any
ControlLogix controller in the control system.
The 1756-DHRIO connection can be inhibited on the module
properties connection tab of RSLogix5000.
Inhibiting an Remote I/O
Connector Adapter
When the inhibit bit is set for a remote I/O adapter connection, the
connection between the ControlLogix controller and the remote I/O
adapter is terminated.
In this case, the 1756-DHRIO scanner (Channel A or B) continues to
scan the remote I/O rack on the remote I/O network and switches the
affected chassis of I/O into program mode. Only the ControlLogix
controller that initiated the configuration of the 1756-DHRIO module
can reestablish communications with the inhibited remote I/O
adapter.
RIO rack connections can be inhibited on the module properties
connection screen of RSLogix 5000.