Rockwell Automation T3418F ICS Regent Monitored Digital Input Modules, Field Powered (Type F) - Manual (Page 4)

Monitored Digital Input Modules, Type F (T3411F, T3418F)
4
Industrial Control Services
The bus drivers then move the data onto the I/O Safetybus
which, in turn, passes it to the processors.
Each module’s voter circuits are periodically tested by the
processor modules. Discrepant data are sent through one of
three legs of the I/O Safetybus to determine whether the
module’s voter is able to outvote the incorrect data. A failure
to return the correct majority-voted result to the processors
produces an I/O module error indication at the processor
modules and a module fault indication at the I/O module.
Each type of module has a unique identification code that is
read by the controller. This code lets the controller know
which type of module is installed in each I/O chassis slot and
address that module and its points specifically. The processor
modules periodically check each module’s identification code
to determine whether the type of module installed matches
type of module indicated in the I/O configuration that was
loaded when the system was started. If a module is removed,
or is replaced with a module of a different type, the processor
modules will indicate I/O module errors.
Loopback logic tests periodically write data to the module and
then read it back to determine whether the module’s I/O bus
interface logic is functioning correctly.
Input Circuit Testing
The field interface circuits of the monitored input module are
completely tested to detect stuck-on or stuck-off input circuit
faults and optionally identify input wiring open and short
circuits. The automatic execution and evaluation of the input
testing is controlled by the triplicated Regent processor
modules.
During normal operations, the internal reference voltage is
set to three levels and the comparator output is read. These
three reference voltage levels represent thresholds that
determine whether the input signal is on or off and if the field
wiring is open circuit or short circuit. The logic-side FPGA
determines input status and line fault status based on the
comparator data for the three voltage levels. The FPGA data
is provided to the I/O processors for application processing.
On a background basis, the I/O processors test the input
circuit comparators and logic circuits for stuck-on and stuck-