Using An External Source; Routing Ao Sample Clock To An Output Terminal; Other Timing Requirements; Ao Sample Clock Timebase Signal - National Instruments Data Acquisition Device NI USB-621x User Manual

Chapter 5 Analog Output

AO Sample Clock Timebase Signal

NI USB-621x User Manual

Using an External Source

Use any input PFI line as the source of AO Sample Clock.

Routing AO Sample Clock to an Output Terminal

You can route AO Sample Clock (as an active low signal) out to any output
PFI terminal.

Other Timing Requirements

A counter on your device internally generates AO Sample Clock unless you
select an external source. AO Start Trigger starts the counter and either the
software or hardware can stop it once a finite generation completes. When
using an internally generated AO Sample Clock, you also can specify a
configurable delay from AO Start Trigger to the first AO Sample Clock
pulse. By default, this delay is two ticks of AO Sample Clock Timebase.
Figure 5-6 shows the relationship of AO Sample Clock to AO Start Trigger.
AO Sample Clock Timebase
AO Sample Clock
Figure 5-6. AO Sample Clock and AO Start Trigger
The AO Sample Clock Timebase (ao/SampleClockTimebase) signal is
divided down to provide a source for AO Sample Clock.
You can route any of the following signals to be the AO Sample Clock
Timebase signal:
• 20 MHz Timebase
• 100 kHz Timebase
• (USB-6211/6215 Devices)
AO Start Trigger
PFI <0..3>
5-8
Delay
From
Start
Trigger
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