National Instruments Data Acquisition Device E Series User Manual page 120

The Master Timebase signal can only be accepted as an external signal over RTSI.
Note
Refer to the
Bus (RTSI), for information about routing this signal.
© National Instruments Corporation
RTSI Trigger <0..6>
PFI <0..9>
Onboard Clock
Ctr0InternalOutput
Figure 7-1. ai/ConvertClock Signal Routing
Figure 7-1 shows that ai/Convert Clock can be generated from a number of
sources, including the external signals RTSI <0..6> (PCI and PXI buses
only) and PFI <0..9> and the internal signals, Onboard Clock and
Ctr0InternalOutput.
On PCI and PXI devices, many of these timing signals are also available as
outputs on the PFI pins.
Device and RTSI Clocks section of Chapter 8,
7-3
Chapter 7 Digital Routing
ai/ConvertClock
Real-Time System Integration
E Series User Manual