User`s guide

Using the Digital Port Appendix C
Model N6705 User’s Guide 203
Fault/Inhibit System Protection
As shown in the following figure, when the Fault outputs and Inhibit
inputs of several mainframes are daisy-chained, an internal fault
condition in one of the mainframes will disable all of them 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.
As shown in the figure above, 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 output
channels in the mainframe. 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 (sourced by the
Inhibit signal), as previously explained under "Inhibit Input".
NOTE
Even when the initial fault condition or external signal is removed, the Inhibit
fault signal is still active and will continue to shut down all mainframe outputs.
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
mainframe as explained in chapter 3. If the operating mode of the
Inhibit input is Latched, turn off the Inhibit input on
ALL mainframes
individually. To re-enable the chain, re-program the Inhibit input on
each mainframe 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.
FLT
INH
1 2 3 4 5 6 7
I
1 2 3 4 5 6 7
I
1 2 3 4 5 6 7
I
FLT
INH
FLT
INH
+ - + -
+ -