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7-21GFK-0787B Chapter 7 Programming Information
Programming for Fault and Alarm Contacts
The GMR system software can optionally utilize the Fault and Alarm contacts capability of the
Series 90-70 PLC to make fault and alarm information available to the application program logic.
Conditions that cause Fault and Alarm contacts to be set are described in the Diagnostics chapter.
Programming for Fault and Alarm contacts is explained on the following pages.
Fault and No Fault Contacts
Fault and No Fault contacts can be used to detect fault or lack of fault conditions on a
discrete (%I or %Q) or analog (%AI or %AQ) reference. They can also be programmed
with the Series 90-70’s built-in fault-locating references (see below). Unless they are used
ONLY with fault-locating references, fault memory for their use must be set up using
the CPU Configuration function of the Logicmaster 90 software.
A Fault contact is programmed as shown below, using the reference address to be monitored
(here, %I0014):
%I0014
[FAULT]
%Q0056
( )
A Fault contact passes power flow if the associated reference has a fault. (Fault contacts are
also set if a block logs off the bus.)
A similar contact, called the No Fault contact passes power flow while the associated
reference has no fault.
%I0167
[NOFLT]
%Q0168
( )
Clearing Faults Associated with Fault/No Fault Contacts
When used with a %I, %Q, %AI, or %AQ reference, a fault associated with the [FAULT] contact
must be cleared to remove it from the fault table and stop the contact from passing power
flow. Fault contacts are cleared by being reset from the application program, by sending a
command to the GMR software using the %M bit for I/O Reset (%M12258). Clearing such a fault
with a Hand-held Monitor does not remove it from the fault table or stop the contact passing power flow.
Fault-Locating References
Both Fault and No-Fault contacts can be programmed with fault-locating references to
identify faults associated with the system hardware. These fault references are for
informational purposes only. The PLC does not halt execution if one of these reference
faults occurs. For a Genius device, the format of the fault-locating reference is:
M_rsbmm
Where r is the rack number 0 to 7, s is the slot number of the bus controller; b is the bus
number, and mm is the serial bus address of the affected Genius device. For example,
M_46128 represents rack 4, slot 6, bus 1, module 28. For more information about
fault-locating references, please refer to the Logicmaster 90-70 Software User’s Manual.