Rockwell Automation 57C421B Pulsetach Input Module/DCS 5000/AutoMax - Manual (Page 48)

5Ć6
5.3.1 No Interrupts
If interrupts are never received and the timeout parameter in the
hardware EVENT statement in the task is disabled, the task will
never execute and there will be no error codes displayed on the
Processor module:
Step 1.
Verify that the application task is correct.
Verify that your interrupt response task is checking the
proper interrupt acknowledge bit to determine which bit
caused the interrupt. Confirm that when an interrupt is
located the interrupt acknowledge bit is being reset. If this
is not done, the interrupt will occur once and will not
occur again.
Step 2. Verify that the inputs are wired correctly.
Confirm that all terminal strip connections are tight. Use
an oscilloscope and check the pulses coming from the
pulsetach. The duration of the pulse should be at least 8
microseconds. The square wave signals should be free of
electrical noise. If electrical noise is present, check the
ground connections and increase the signal's shielding
as necessary.
If external inputs are used, connect a voltmeter to the
proper points on the terminal strip and toggle each
external device. The voltmeter should alternate between 0
and maximum voltage. If this does not happen, there is a
problem with either the device or the wiring to the
terminal strip.
Step 3. Verify that the input circuit on the module is working
correctly.
Remove power from the system. Disconnect the
mechanical coupling between the motor and the
pulsetach. Apply power to the rack and the pulsetach.
Move the pulsetach in both directions. The FORWARD
LED on the faceplate should turn on when the pulsetach
is rotated in the forward direction. The REVERSE LED
should turn on when the pulsetach is rotated in the
opposite direction.
If the pulsetach rotates in the wrong direction, the
pulsetach input wires must be switched. In a
singleĆended wiring configuration, swap the A and B
inputs. In a differential wiring configuration, swap the A
and not A inputs.
Remove power from the rack and the pulsetach.
ReĆconnect the coupling between the motor and the
pulsetach. ReĆapply power to the system.
If external inputs are used, toggle the input device and
verify that the appropriate LEDs on the module's
faceplate are also toggling. If they are not, the input
circuit on the module is not working properly.
Step 4. Verify that the module can be accessed.
Connect an IBMĆcompatible personal computer to the
system and load the Programming Executive software.
Refer to the AutoMax Programming Executive instruction
manual for more information.