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5-2 Genius Modular Redundancy Flexible Triple Modular Redundant (TMR) System
User’s Manual –March 1995
GFK-0787B
Diagnostics in a GMR System
In a GMR system, extensive diagnostic capabilities are provided by standard Genius I/O
diagnostics and by the special autotesting and discrepancy reporting features of the GMR
software. Standard Genius diagnostics, which are covered in other books, are not described in
detail here.
Each PLC provides a full range of fault table and program access to fault information.
Input Diagnostics
Genius Diagnostics:
Line fault. a feature of the 16-circuit DC blocks. To report line faults, an input must be
configured for tristate operation and installed as explained on page 5-14.
For blocks in GMR mode, a line fault represents a short circuit fault on the field wiring.
For blocks in any other mode, a line fault represents an open circuit fault in the field
wiring.
Autotest Diagnostics. for discrete inputs configured for autotesting., autotesting
determines whether inputs can attain their opposite state (alarm state) and checks for
channel to channel shorts.
Discrepancy Reporting: between the raw input data from each bus and the
corresponding voted inputs.
Output Diagnostics
Genius Diagnostics:
No-load fault: For 16-circuit blocks only, individual outputs can be configured to
enable or disable reporting No-load faults. The minimum load current required
to assure proper no-load reporting is 100mA (not 50mA, as it would be for a
block not used in a GMR group). For an individual block:
If outputs are On with no output load, no-load fault reports may be
generated at any time except during a Pulse Test.
If outputs are Off with no output load, no-load fault reports are generated
during a Pulse Test.
Short circuit fault.
Overtemperature fault.
Overload fault
Failed switch:. Occurs if the actual output state differs from the commanded state.
Autotest Diagnostics. for discrete outputs configured for autotesting. Autotesting
determines whether outputs can attain the opposite of their normal state.
Output Discrepancy Reporting: Blocks configured for GMR mode operation report to
each PLC the discrepancy status for the data from each PLC, together with each
PLC ’s online/offline status.