NI DIGITAL PATTERN DRIVER TDR Functions

TDR Functions

• niDigital_TDR
• niDigital_ApplyTDROffsets

niDigital_TDR

Measures propagation delays through cables, connectors, and load boards using Time-Domain Reflectometry (TDR).

Ensure that the channels and pins you select are connected to an open circuit.

C Function Prototype: ViStatus niDigital_TDR (ViSession vi, ViConstString channelList, ViBoolean applyOffsets, ViInt32 offsetsBufferSize, ViReal64[] offsets, ViInt32* actualNumOffsets)

Parameter	Description
vi	The specified instrument session the niDigital_init or niDigital_InitWithOptions function returns.
channelList	List of channel names or list of pins. Do not pass a mix of channel names and pin names. An empty string denotes all digital pattern instrument channels. Pin names and pin groups apply to all enabled sites, unless the pin name explicitly specifies the site. You can specify a pin in a specific site using the form siteN/pinName, where N is the site number. This function ignores pins that are not mapped to the digital pattern instrument. Specify channel names using the form PXI1Slot3/0,2-3 or PXI1Slot3/0,PXI1Slot3/2-3, where PXI1Slot3 is the instrument resource name and 0, 2, 3 are channel names. To specify channels from multiple instruments, use the form PXI1Slot3/0,PXI1Slot3/2-3,PXI1Slot4/2-3. The instruments must be in the same chassis.
applyOffsets	A Boolean that specifies whether to apply the measured TDR offsets. If you need to adjust the measured offsets prior to applying, set this input to VI_FALSE, and call the niDigital_ApplyTDROffsets function to specify the adjusted TDR offsets values.
offsetsBufferSize	The number of elements in the ViReal64 array you specify for offsets. To determine the size of the buffer to allocate for the offsets array, pass a value of 0 to the offsetsBufferSize parameter and a value of VI_NULL to the offsets parameter. In this case, the value returned by the actualNumOffsets parameter is the size of the array necessary to hold the TDR offsets.
Output
offsets	Measured TDR offsets specified in seconds.
actualNumOffsets	Number of offsets written to the offsets array.

Return value: Reports the status of the operation.

niDigital_ApplyTDROffsets

Applies the correction for propagation delay offsets to a digital pattern instrument. Use this function to apply TDR offsets that are stored from a past measurement or are measured by means other than the niDigital_TDR function. Also use this function to apply correction for offsets if the applyOffsets input of the niDigital_TDR function was set to False at the time of measurement.

C Function Prototype: ViStatus niDigital_ApplyTDROffsets (ViSession vi, ViConstString channelList, ViInt32 numOffsets, ViReal64[] offsets)

Parameter	Description
vi	The specified instrument session the niDigital_init or niDigital_InitWithOptions function returns.
channelList	List of channel names or list of pins. Do not pass a mix of channel names and pin names. An empty string denotes all digital pattern instrument channels. Pin names and pin groups apply to all enabled sites, unless the pin name explicitly specifies the site. You can specify a pin in a specific site using the form siteN/pinName, where N is the site number. This function ignores pins that are not mapped to the digital pattern instrument. Specify channel names using the form PXI1Slot3/0,2-3 or PXI1Slot3/0,PXI1Slot3/2-3, where PXI1Slot3 is the instrument resource name and 0, 2, 3 are channel names. To specify channels from multiple instruments, use the form PXI1Slot3/0,PXI1Slot3/2-3,PXI1Slot4/2-3. The instruments must be in the same chassis.
numOffsets	Number of offsets.
offsets	TDR offsets to apply, in seconds. Specify an offset for each pin or channel in the channelList. If the channelList contains pin names, you must specify offsets for each site in the channel map per pin.

Return value: Reports the status of the operation.