Reactions To Faults In The Input Modules - Allen-Bradley AADvance T9110 Safety Manual

The input module can be configured to operate in SIL 2 or SIL 3
configurations for energize to action and de-energize to trip applications. The
module provides the following isolation:
• channel to channel galvanic isolation
• galvanic isolation between channels and the communication signals
• galvanic isolation between channels and power
• locking screw operational function

Reactions to faults in the input modules

When an input channel is not capable of reporting a voltage within the safety
accuracy specified for the module, then the module returns safe values to the
processor. Signals go to a safe state if the module scan time exceeds the PST
(refer to "Input Module Safety Accuracy" for safe state details). All I/O
modules provide front panel indications, store fault codes in the fault log and
can also report via the workbench application variables. The following status
information is provided:
• module presence
• module health and status
• channel health and status
• field faults
• an echo of the front panel indicators for each module
Availability of input modules
Input modules support redundancy when configured for dual or triple
operation using the appropriate termination assembly. Redundant input
modules may be inserted or removed at any time without any impact on the
safety function of the system. Redundant input modules operate
independently providing independent values of the input values to the
processor module.
Termination Assemblies
The termination assemblies are safety critical and provide termination for 16
channels. They connect the field signals to the input modules. The simplex
version connects each input channel to one input module, the dual TA routes
them to two input modules and the triple TA to three input modules.
Digital and analogue input TA circuits both have fuse protection and a high
reliability input load for each channel.
Rockwell Automation Publication ICSTT-RM446N-EN-P - April 2018
AADvance Functional Safety System Implementation Chapter 4
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