Chapter 10 Digital Routing and Clock Generation
NI 6238/6239 User Manual 10-6 ni.com
Using RTSI Terminals as Timing Input Signals
You can use RTSI terminals to route external timing signals to many
different MSeries functions. Each RTSI terminal can be routed to any of
the following signals.
• AI Convert Clock
• AI Sample Clock
• AI Start Trigger
• AI Reference Trigger
• AI Pause Trigger
• AI Sample Clock Timebase
•AO Start Trigger
• AO Sample Clock
• AO Sample Clock Timebase
• AO Pause Trigger
• Counter input signals for either counter—Source, Gate, Aux,
HW_Arm, A, B, or Z
Most functions allow you to configure the polarity of PFI inputs and
whether the input is edge or level sensitive.
RTSI Filters
You can enable a programmable debouncing filter on each PFI, RTSI, or
PXI_STAR signal. When the filters are enabled, your device samples the
input on each rising edge of a filter clock. M Series devices use an onboard
oscillator to generate the filter clock with a 40MHz frequency.
Note NI-DAQmx only supports filters on counter inputs.
The following is an example of low-to-high transitions of the input signal.
High-to-low transitions work similarly.
Assume that an input terminal has been low for a long time. The input
terminal then changes from low-to-high, but glitches several times. When
the filter clock has sampled the signal high on N consecutive edges, the
low-to-high transition is propagated to the rest of the circuit. The value of
N depends on the filter setting; refer to Table10-2.