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Chapter 4
Digital Input/Output and PFI
Digital Output Triggering Signals
Digital output supports two different triggering actions: DO Start Trigger and DO Pause Trigger.
A digital or analog trigger can initiate these actions. Any PFI terminal can supply a digital
trigger, and some C Series analog modules can supply an analog trigger. For more information,
refer to the documentation included with your C Series module(s).
Refer to the
sections for more
information about the digital output trigger signals.
Digital Output Timing Signals
The cDAQ chassis features the following DO timing signals:
•
•
DO Sample Clock Timebase Signal
•
•
Signals with an * support digital filtering. Refer to the
section for more information.
DO Sample Clock Signal
The DO Sample Clock (do/SampleClock) signals when all the digital output channels in the task
update. DO Sample Clock can be generated from external or internal sources as shown in
Figure 4-4.
Figure 4-4.
Digital Output Timing Options
Routing DO Sample Clock to an Output Terminal
You can route DO Sample Clock to any output PFI terminal. DO Sample Clock is active high
by default.
Programmable
Clock
Divider
DO Sample Clock
Timebase
PFI
Analog Comparison Event
Ctr
n Internal Output
DO Sample Clock
Analog Comparison
Event
20 MHz Timebase
80 MHz Timebase
PFI
100 kHz Timebase
