Appendix B Timing Diagrams
M Series User Manual B-6 ni.com
The second level of timing is the sample level. Basically, converts are
grouped in sets called samples, and the timing of the samples can be
independent from the timing of the converts. The M Series device can use
a timebase to generate the sample timing. This timebase is called Sample
Clock Timebase. This signal can be internal (for example, an internal
timebase) or external. Either way, the signal gets divided in the SI counter
and used to generate Sample Clock signals (which in turn, signal the start
of a sample). In order to synchronize external triggers to the Sample Clock
Timebase, another related signal is created, Sync Sample Clock Timebase.
This is always the inverted signal selected to be Sample Clock Timebase,
while the Sample Clock Timebase signal is a copy without inversion of the
signal. The idea is that for each significant edge of the Sample Clock
Timebase, there is a significant edge of the Sync Sample Clock Timebase
signal that occurs before Sample Clock Timebase and that can be used to
synchronize the input triggers.
The source for Convert Clock Timebase and Sample Clock Timebase is the
internal signal bus, _i. The timing of this signal is described in relation to
this common point. The Convert Clock Timebase and Sample Clock
Timebase can be asynchronous from each other.
Figure B-4. AI Timing Clocks and the Analog Input Timing Engine
Start
Terminal
Selected Reference Trigger
Reference Trigger
Te r m in al
Terminal
Selected Sample Clock
Te r m in al
Terminal
Te r m in al
Selected Start
RTSI
Te r m in al
Terminal
Terminal
Pause Trigger
SI
Counter
Block
SI2
Counter
Block
SI_TC
Sample Clock Timebase
Sync Sample Clock Timebase
Convert Clock Timebase
Sync Convert Clock Timebase
SI Start
Pause Trigger
p_AI_Convert
Start
1
_i
SI2_TC
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