To ensure that synchronization is correct, call the niTClk Synchronize VI or the niTClk_Synchronize function whenever you change a clocking attribute or a sample rate attribute for a TClk-synchronized device. Each call to the niTClk Synchronize VI or the niTClk_Synchronize function adds time to the application execution.

To optimize the performance of your application, set the clocking and sample rate attributes only once, and then call the niTClk Synchronize VI or the niTClk_Synchronize function.

You do not need to call the niTClk Synchronize VI or the niTClk_Synchronize function every time you start an acquisition, unless you change attributes that affect the clocking or the sample rate. The following table lists attributes that affect the clocking or the sample rate. For the 5922 digitizer, the list of attributes also includes channel-based attributes.

Caution NI-TClk does not detect any changes to the relevant attributes. Therefore, NI-TClk does not report errors if the devices become unsynchronized due to an attribute change. You must resynchronize the devices if any of the following attributes change.
Tip Call the niTClk Configure for Homogenous Triggers VI or the niTClk_ConfigureForHomogeneousTriggers function whenever the value of any driver attribute changes.
Driver LabVIEW Property C Attribute Comment
NI-FGEN Sample Rate NIFGEN_ATTR_ARB_SAMPLE_RATE
NI-FGEN Sample Clock Timebase Rate NIFGEN_ATTR_SAMPLE_CLOCK_TIMEBASE_RATE
NI-FGEN Sample Clock Timebase Source NIFGEN_ATTR_SAMPLE_CLOCK_TIMEBASE_SOURCE
NI-FGEN Sample Clock Mode NIFGEN_ATTR_CLOCK_MODE
NI-FGEN Sample Clock Source NIFGEN_ATTR_SAMPLE_CLOCK_SOURCE
NI-FGEN Reference Clock Source NIFGEN_ATTR_REF_CLOCK_SOURCE
NI-FGEN Reference Clock Frequency NIFGEN_ATTR_REF_CLOCK_FREQUENCY
NI-FGEN Frequency NIFGEN_ATTR_FUNC_FREQUENCY Only applies to some devices
NI-FGEN Waveform NIFGEN_ATTR_FUNC_WAVEFORM Only applies to some devices
NI-FGEN OSP Enabled NIFGEN_ATTR_OSP_ENABLED
NI-FGEN IQ Rate NIFGEN_ATTR_OSP_IQ_RATE
NI-FGEN CIC Interpolation Factor NIFGEN_ATTR_OSP_CIC_FILTER_INTERPOLATION
NI-FGEN FIR Interpolation Factor NIFGEN_ATTR_OSP_FIR_FILTER_INTERPOLATION
NI-HSDIO RefClk.Source NIHSDIO_ATTR_REF_CLOCK_SOURCE
NI-HSDIO RefClk.Rate NIHSDIO_ATTR_REF_CLOCK_RATE
NI-HSDIO RefClk.Impedance NIHSDIO_ATTR_REF_CLOCK_IMPEDANCE External reference clock only
NI-HSDIO SampClk.Source NIHSDIO_ATTR_SAMPLE_CLOCK_SOURCE
NI-HSDIO SampClk.Rate NIHSDIO_ATTR_SAMPLE_CLOCK_RATE
NI-HSDIO SampClk.Impedance NIHSDIO_ATTR_SAMPLE_CLOCK_IMPEDANCE External sample clock only
NI-RFSA Digitizer Sample Clock Timebase Source NIRFSA_ATTR_DIGITIZER_SAMPLE_CLOCK_TIMEBASE_SOURCE
NI-RFSA Digitizer Sample Clock Timebase Rate NIRFSA_ATTR_DIGITIZER_SAMPLE_CLOCK_TIMEBASE_RATE
NI-RFSA Ref Clock Source NIRFSA_ATTR_REF_CLOCK_SOURCE
NI-RFSA Ref Clock Rate NIRFSA_ATTR_REF_CLOCK_RATE
NI-RFSG IO Rate NIRFSG_ATTR_IQ_RATE
NI-RFSG Arb Sample Clock Rate NIRFSG_ATTR_ARB_SAMPLE_CLOCK_RATE
NI-RFSG Arb Sample Clock Source NIRFSG_ATTR_ARB_SAMPLE_CLOCK_SOURCE
NI-RFSG Reference Clock Rate NIRFSG_ATTR_REF_CLOCK_RATE
NI-RFSG Reference Clock Source NIRFSG_ATTR_REF_CLOCK_SOURCE
NI-SCOPE Min Sample Rate NISCOPE_ATTR_MIN_SAMPLE_RATE
NI-SCOPE Input Clock Source NISCOPE_ATTR_CLOCK_SOURCE
NI-SCOPE Reference Clock Rate NISCOPE_ATTR_REF_CLK_RATE
NI-SCOPE Sample Clock Timebase Source NISCOPE_ATTR_SAMP_CLK_TIMEBASE_SRC
NI-SCOPE Sample Clock Timebase Rate NISCOPE_ATTR_SAMP_CLK_TIMEBASE_RATE
NI-SCOPE Sample Clock Timebase Divisor NISCOPE_ATTR_SAMP_CLK_TIMEBASE_DIV
NI-SCOPE Max Input Frequency NISCOPE_ATTR_MAX_INPUT_FREQUENCY Only applies to some devices