National Instruments PCI-6281, User Manual

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Chapter 9 Digital Routing and Clock Generation
80 MHz Timebase
The 80 MHz Timebase can be used as the Source input to the 32-bit general-purpose
counter/timers.
The 80 MHz Timebase is 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 also can be used 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
The 100 kHz Timebase can be used to generate many of the AI and AO timing signals. The
100 kHz Timebase also can be used 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.
External Reference Clock
The external reference clock can be used as a source for the internal timebases
(80 MHz Timebase, 20 MHz Timebase, and 100 kHz Timebase) on an M Series device. By
using the external reference clock, you can synchronize the internal timebases to an external
clock.
The following signals can be routed to drive the external reference clock:
• RTSI <0..7>
• PXI_CLK10
• PXI_STAR
The external reference clock is an input to a Phase-Lock Loop (PLL). The PLL generates the
internal timebases.
10 MHz Reference Clock
The 10 MHz reference clock can be used to synchronize other devices to your M Series device.
The 10 MHz reference clock can be routed to the RTSI <0..7> terminals. Other devices
connected to the RTSI bus can use this signal as a clock input.
The 10 MHz reference clock is generated by dividing down the onboard oscillator.