Rockwell Automation 57C421B Pulsetach Input Module/DCS 5000/AutoMax - Manual (Page 49)

5Ć7
Use the MONITOR I/O selection to display registers 6 and
7. Continue to toggle the input device and determine if
the proper bits are changing state. If the bits are not
changing state, the input circuit on the module is not
working.
Step 5. Verify that the hardware is working correctly.
WARNING
INSERTING OR REMOVING A MODULE OR ITS CONNECTING CABLES MAY
RESULT IN UNEXPECTED MACHINE MOTION. TURN OFF POWER TO THE RACK
BEFORE INSERTING OR REMOVING A MODULE OR ITS CONNECTING CABLES.
FAILURE TO OBSERVE THESE PRECAUTIONS COULD RESULT IN BODILY
INJURY.
The problem may be in one of three areas. Replace these
items one at a time and determine whether the problem
has been corrected before attempting to replace the next
item. First replace the Pulsetach Input module, then the
Processor modules, and finally the backplane.
5.3.2 Hardware Event TimeĆout
A hardware event timeĆout results in error code 12" appearing on
the faceplate of the Processor. It means that the interrupt has either
never occurred or is occurring at a slower frequency than the value
specified in the TIMEOUT parameter in the EVENT definition. When
this timeĆout occurs all tasks in the rack will stop:
Step 1.
Verify that the TIMEOUT value is set correctly.
Check the value specified in the TIMEOUT parameter in
the event definition. The number is in ticks. The tick value
defaults to 5.5 msec. The timeĆout value should be at
least 2 ticks greater than the interrupt frequency. It is
usually 1.5 times the interrupt frequency.
Step 2. Check for a no interrupt condition". See section 5.3.1.
The TIMEOUT parameter in the EVENT statement should
be disabled if interrupts are not timeĆbased. See section
4.4.3 for an example.
5.3.3 Hardware Event Count Limit Exceeded
This condition results in error code 1b" appearing on the faceplate
of the Processor module. It means that a hardware interrupt has
occurred and no task is waiting. When this error occurs all tasks in
the rack will stop:
Step 1.
Verify that the application task is correct.
Verify that your interrupt response task contains either a
WAIT ON" event or CALL SCAN_LOOP" statement that
will be executed. Check carefully to determine whether a
higher priority task is preventing the interrupt response
task from running.