HEIDENHAIN iTNC 530 Service Manual page 394

With the logic diagram you can check the chronological switching behavior of the MB keys:
Figure: Recording of NC START and NC STOP buttons in the logic diagram
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Switch on the machine.
Press the EMERGENCY STOP button.
Call the logic diagram. --> See "The LOGIC diagram" on page 11 – 125.
Define the INPUTs for the following recording.
Start the recording.
Press the keys. --> The respective inputs must change to 1!
Exception: I147 = NC STOP, changes to 0 when actuated (broken wire interlock!)
Note
If a key does not produce a reaction of the control, one does not know, whether the
pushbutton itself or the machine operating panel PCB, the MB cable or the control is
defective.
If required, further tests can be performed. --> See following descriptions!
HEIDENHAIN Service Manual iTNC 530