User Guide

External Source Mode

In external source mode, the chassis generates a delayed Source signal by

delaying the Source signal by several nanoseconds. The NI cDAQ-9172

chassis synchronizes signals on the rising edge of the delayed Source signal

and counts on the following rising edge of the source, as shown in

Figure 48.

Figure 48. External Source Mode

Digital Routing and Clock Generation

The digital routing circuitry has the following functions:

• Manages the flow of data between the bus interface and the

acquisition/generation sub-systems (analog input, analog output,

digital I/O, and the counters). The digital routing circuitry uses FIFOs

(if present) in each sub-system to ensure efficient data movement.

• Routes timing and control signals. The acquisition/generation

sub-systems use these signals to manage acquisitions and generations.

These signals can come from the following sources:

– Your C Series I/O modules

– User input through the PFI terminals using correlated digital

C Series I/O modules in slots 5 and/or 6

• Routes and generates the main clock signals for the NI cDAQ-9172

chassis.

To determine the signal routing options for C Series I/O modules

installed in the NI cDAQ-9172 chassis, refer to the Device Routes tab

in MAX.

Source

Delayed Source

Synchronize

Count