User Guide

NI cDAQ-9172 User Guide and Specifications 76 ni.com
Clock Routing
Figure 49 shows the clock routing circuitry of the NI cDAQ-9172 chassis.
Figure 49. NI cDAQ-9172 Clock Routing Circuitry
80 MHz Timebase
You can use the 80 MHz Timebase as the Source input to the 32-bit
general-purpose counter/timers.
The 80 MHz Timebase can be generated from the following sources:
• Onboard oscillator
• External signal (by using the external reference clock)
20 MHz Timebase
The 20 MHz Timebase normally generates many of the AI and AO timing
signals. The 20 MHz Timebase can function as the Source input to the
32-bit general-purpose counter/timers.
The 20 MHz Timebase is generated by dividing down the
80 MHz Timebase.
100 kHz Timebase
You can use the 100 kHz Timebase to generate many of the AI and AO
timing signals. The 100 kHz Timebase can also function as the Source
input to the 32-bit general-purpose counter/timers.
The 100 kHz Timebase is generated by dividing down the 20 MHz
Timebase by 200.
÷ 4
÷ 200
80 MHz Timebase
100 kHz Timebase
20 MHz Timebase
Onboard
80 MHz
Oscillator