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6 Advanced Source, Measurement, and Control
Fault/Inhibit System Protection
The following figure illustrates some ways that you can connect the Fault/Inhibit pins of the
connector.
As shown in the figure, when the Fault outputs and Inhibit inputs of several instruments are daisy-
chained, an internal fault condition in one of the units will disable all outputs without intervention by
either the controller or external circuitry. Note that when using the Fault/Inhibit signals in this manner,
both signals must be set to the same polarity.
You can also connect the Inhibit input to a manual switch or external control signal that will short the
Inhibit pin to common whenever it is necessary to disable all outputs. Negative polarity must be
programmed for all pins in this case. You can also use the Fault output to drive an external relay circuit
or signal other devices whenever a user-definable fault occurs.
Clearing a System Protection Fault
To restore all instruments to a normal operating condition when a fault condition occurs in a daisy-
chained system protection configuration, two fault conditions must be removed:
1. The initial protection fault or external Inhibit signal.
2. The subsequent daisy-chained fault signal (which is sourced by the Inhibit signal).
Even when the initial fault condition or external signal is removed, the fault signal is
still active and will continue to shut down the outputs of all the units.
To clear the daisy-chained fault signal if the operating mode of the Inhibit input is Live, simply clear the
output protection on any ONE unit as explained under
mode of the Inhibit input is Latched, turn off the Inhibit input on ALL units individually. To re-enable the
chain, re-program the Inhibit input on each unit to Latched mode.
Trigger Input
Any of the Digital Control pins can be programmed to function as a trigger input. All pins are
referenced to the Signal Common pin.
To input an external trigger signal, you can apply either a negative-going or a positive-going pulse to
the designated trigger input pin. The trigger latency is 5 microseconds. The minimum pulse width is 2
230
Clearing Protection
Functions. If the operating
Keysight N6705C User's Guide
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