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NI-DAQmx Base 3.x C Function Reference Help
Conventions
Related Documentation
Key Concepts
Clocks
Terminal Names
Task Configuration/Control
DAQmxBaseClearTask
DAQmxBaseCreateTask
DAQmxBaseIsTaskDone
DAQmxBaseLoadTask
DAQmxBaseResetDevice
DAQmxBaseStartTask
DAQmxBaseStopTask
Channel Configuration/Creation
Create Analog Input Channels
DAQmxBaseCreateAIThrmcplChan
DAQmxBaseCreateAIVoltageChan
Create Analog Output Channel
DAQmxBaseCreateAOVoltageChan
Create Digital Input Channels
DAQmxBaseCreateDIChan
Create Digital Output Channels
DAQmxBaseCreateDOChan
Create Counter Input Channels
DAQmxBaseCreateCIPeriodChan
DAQmxBaseCreateCICountEdgesChan
DAQmxBaseCreateCIPulseWidthChan
Position
DAQmxBaseCreateCILinEncoderChan
DAQmxBaseCreateCIAngEncoderChan
Create Counter Output Channels
DAQmxBaseCreateCOPulseChanFreq
Timing
DAQmxBaseCfgSampClkTiming
DAQmxBaseCfgImplicitTiming
Triggering
Start Trigger
DAQmxBaseDisableStartTrig
DAQmxBaseCfgDigEdgeStartTrig
DAQmxBaseCfgAnlgEdgeStartTrig
Reference Trigger
DAQmxBaseCfgAnlgEdgeRefTrig
DAQmxBaseCfgDigEdgeRefTrig
DAQmxBaseDisableRefTrig
Read Functions
DAQmxBaseReadAnalogF64
DAQmxBaseReadBinaryI16
DAQmxBaseReadCounterF64
DAQmxBaseReadCounterScalarF64
DAQmxBaseReadCounterScalarU32
DAQmxBaseReadCounterU32
DAQmxBaseReadDigitalScalarU32
DAQmxBaseReadDigitalU32
DAQmxBaseReadDigitalU8
Write Functions
DAQmxBaseWriteAnalogF64
DAQmxBaseWriteDigitalU8
DAQmxBaseWriteDigitalU32
DAQmxBaseWriteDigitalScalarU32
Export HW Signals
DAQmxBaseExportSignal
Internal Buffer Configuration
DAQmxBaseCfgInputBuffer
Error Handling
DAQmxBaseGetExtendedErrorInfo
Glossary
Important Information
Warranty
Copyright
Trademarks
Patents
WARNING REGARDING USE OF NATIONAL INSTRUMENTS PRODUCTS
Environmental Management
Technical Support and Professional Services

Clocks

Periodic digital edges measure time and are called clocks. Clocks such as a sample timebase clock and the 20 MHz timebase clock mark the passing of time or are used to align other signals in time. Clocks usually do not cause actions in the sense that triggers do. The names of clocks usually do not refer to actions. The sample clock is a notable exception.

Clocks in NI-DAQmx

  • AI Convert Clock—The E Series clock that directly causes ADC conversions.
  • AI Convert Clock Timebase—The clock that is divided down to produce the AI convert clock.
  • AI Sample Clock—The clock that controls the time interval between samples. Each time the sample clock ticks (produces a pulse) one sample per channel is acquired.
  • AI Sample Clock Timebase—The clock used as the onboard clock source of the sample clock. When the source of the sample clock is set to the onboard clock, the Sample Clock Timebase is divided down to produce the sample clock. When the source of the Sample Clock Timebase is also the onboard clock, the master timebase is divided down to produce the Sample Clock Timebase.
  • AO Sample Clock—The clock that controls the time interval between samples. Each time the sample clock ticks (and produces a pulse), one sample per channel is generated.
  • AO Sample Clock Timebase—The onboard clock used as the source of the AO sample clock. The AO Sample Clock Timebase is divided down to produce the AO sample clock.
  • Counter Timebase—The clock connected to the Source terminal of a counter (Ctr0Source, for example).
  • Master Timebase—An onboard clock used by other counters on the device. The master timebase is divided down to produce a slower clock or to measure elapsed time. This timebase is the onboard clock used as the source of the AI Sample Clock timebase, the AO Sample Clock timebase, and the counter timebases, for example.
  • 20 MHz Timebase—The onboard clock source for the master timebase from which other timebases are derived.
  • 100 kHz Timebase—The clock produced by dividing the 20 MHz Timebase by 200.

Trigger and Clock Confusion

The distinction between triggers and clocks is blurred when the digital edges used as a trigger are periodic. In such a case, a clock causes the device to perform an action. The sample clock is the primary example. The stimulus for the action of producing a sample is so often a clock that NI-DAQmx Base configures the sample clock instead of the sample trigger. The distinction is made clear when you consider the sample clock is in fact just one way of providing the source of a sample trigger.

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