Rockwell Automation 1715-OF8I Redundant I/O System User Manual - Manual (Page 134)

134 Rockwell Automation Publication 1715-UM001C-EN-P - March 2014
Chapter 3 Digital I/O Operation
Monitor Fault Bits
The Output Data Echo matches only the commanded state of the outputs if the
module is operating under normal conditions. If there is an anomaly with the
module, the commanded state and the Output Data Echo may not match.
You can monitor the fault bits for your output points for fault conditions. If a
fault occurs, the fault bit is set and your program alerts you to the condition. In
this case, the output data echo may not match the commanded state of the
outputs.
If there is a mismatch between the commanded state of the outputs and the
Output Data Echo, check your output module for these conditions:
• Communication fault
• Connection is inhibited
• Blown fuse - Module does not turn on output if overload/short circuit is
detected
Fusing
Some digital outputs have internal electronic or mechanical fusing to prevent too
much current from flowing through the module. This feature protects the
module from electrical damage. Other modules require external fusing.
The 1715-OB8DE module uses electronic fusing.
You can reset an electronic fuse through the Logix Designer application or
through ladder logic running on a controller. This feature has a corresponding tag
that can be examined in the user program in the event of a fault.
See Table 18 to determine what fuse to use in your application.
Table 18 - Recommended Fuses
Circuit Type Cat. No. Fusing on the module Recommended Fuse
DC 1715-OB8DE (1) (2) (3) Yes - Fused on a per point basis Electronically fused
(1) Electronic protection is not intended to replace fuses, circuit breakers, or other code required wiring protection devices.
(2) The electronic protection of this module has been designed to provide protection for the module from short circuit conditions. The protection is based on a thermal cut-out principle. In the event of a short
circuit condition on an output channel, that channel limits the current within milliseconds after its thermal cut-out temperature has been reached.
(3) The module does not provide protection against reverse polarity or wiring to AC power sources.