National Instruments NI 6221, User Manual

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Appendix B Timing Diagrams
© National Instruments Corporation B-3 M Series User Manual
that will be divided by the SI2 counter, or can be an external Convert
Clock signal. Sync Convert Clock Timebase is a signal related to
Convert Clock Timebase that is used to synchronize external signals
before they are used by circuits running from Convert Clock Timebase.
• Sample Clock Timebase and Sync Sample Clock
Timebase
—Sample Clock Timebase is the source for the SI counter
and can be used to generate the sample timing. Each Sample Clock in
turn triggers the generation of one or more converts. This signal can be
an internal or external timebase. Sync Sample Clock Timebase is a
signal related to Sample Clock Timebase that is used to synchronize
external signals before they are used by circuits running from Sample
Clock Timebase.
• Selected Start and Start —Start is the signal that starts the analog
input timing engine. This signal can come from external signals, a
software command, or internal sources. Selected Start is the signal
chosen to be the Start before it is synchronized (just after the selection
mux).
• Selected Reference Trigger and Reference Trigger —A Reference
Trigger is a trigger that can stop the AI timing engine. If the Reference
Trigger is enabled, the AI timing engine will stop acquiring data once
it sees a valid event on the Reference Trigger and it has acquired the
posttrigger number of samples. This signal can come from external
signals, a software command, or internal sources. The Selected
Reference Trigger is the signal chosen to be the Reference Trigger
before it is synchronized (just after the selection mux).
• Selected Sample Clock and Sample Clock —Selected Sample Clock
is the signal selected to become Sample Clock before any
synchronization (just after the selection mux). The Sample Clock
marks the beginning of a new sample. This signal can be an external or
internal signal. When an internal signal, it can be generated with the
SI counter dividing the Sample Clock Timebase signal. It also can
come from an external terminal or from a signal from another internal
resource inside the M Series device.
• Selected Pause Trigger and Pause Trigger —The Pause Trigger can
be used to pause the acquisition for a certain period of time. Selected
Pause Trigger is the signal that becomes the Pause Trigger signal
before synchronization.
• p_AI_Convert —The signal that starts the conversions of data at the
ADC component. This signal goes directly to the ADC, but copies can
be routed to output terminals.