Rockwell Automation T7491 ICS Regent+Plus Mixed I/O Modules - Manual (Page 4)

Multiplexed I/O Module (T7491)
4
Industrial Control Services
Standard Module Testing
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
how to address that module and its points specifically. 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.
Multiplexed I/O Module Testing
Additional tests are periodically performed to verify the
correct operations of the microprocessor, ROM, RAM and
serial interface to the remote MIU equipment. Detected
failures are reported back to the processor modules as either
fatal or non-fatal errors.
Fatal Errors
Fatal errors are reported when the diagnostics detect a failure
in the module’s electronics. For example, failures in the
microprocessor, RAM, or ROM are considered fatal errors. A
fatal error will result in a module fault indication.
Non-Fatal Errors
Non-fatal errors are reported when failures occur in
communications to the connected MIU equipment. These
failures would represent problems with the serial
communications cables, or the connected MIU processor.
These types of failures are indicated on the face of the module
as a Port fault.