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Frequency Output can be routed out to any PFI terminal. All PFI terminals are set to
high-impedance at startup. The FREQ OUT signal also can be routed to many internal timing
signals.
In software, program the frequency generator as you would program one of the counters for
pulse train generation.
For information about connecting counter signals, refer to the
section.
Frequency Division
The counters can generate a signal with a frequency that is a fraction of an input signal. This
function is equivalent to continuous pulse train generation. Refer to the
section for detailed information.
For information about connecting counter signals, refer to the
section.
Watchdog Timer
The watchdog timer is a software-configurable feature used to set critical outputs to expiration
states in the event of a software failure, a system crash, or any other loss of communication
between the application and the cDAQ chassis.
When the watchdog timer is enabled, if the cDAQ chassis does not receive a watchdog reset
software command within the time specified for the watchdog timer, the outputs go to a
user-defined expiration state and remain in that state until the watchdog timer is disarmed by a
device reset. After the watchdog timer expires, the cDAQ chassis cannot perform any operation
until the cDAQ chassis is reset.
You can set the watchdog timer timeout period to specify the amount of time that must elapse
before the watchdog timer expires. The counter on the watchdog timer is configurable up to
(2
32
- 1) × 25 ns (approximately 107 seconds) before it expires. When a watchdog timer expires,
analog output, digital output, and counter output changes may be configured to transition to an
expiration state.
Resetting the chassis after a watchdog expiration event results in all module outputs defaulting
to power up or startup states as defined in the module specifications.
Note
Resetting the chassis after a watchdog expiration event may result in
undefined transient behavior on the outputs of the NI 9269 and NI 9474 modules.
Consult the module specifications for the expected I/O behavior.
Note
Restarting or re-reserving the chassis may lead to undefined transient
behavior on the outputs of any modules, so these operations are not recommended as
means of a watchdog expiration event recovery.