Measurement-computing UL for NI LabVIEW Instrukcja Użytkownika Pobierz pdf (Strona 102)

Universal Library Virtual Instruments (VIs) Miscellaneous VIs

CurCount Specifies how many points have been input or output. It can be used to gauge how

far along the operation is towards completion. Generally the

CurCount will return

the total number of samples collected at the time of the call to

cbGetStatus().

However, in cases where

CONTINUOUS and BACKGROUND options are both set, the

way that

CurCount behaves will depend on board type and transfer mode. This

value may recycle as the circular buffer recycles, or may continuously increment

with the number of counts transferred. Also,

CurCount may not update on each

sample. For example, when running in

BLOCKIO mode, CurCount will update after

each packet of data has been transferred. The packet size is board dependent. Refer

to board-specific information for details.

CurIndex This is an index into the data buffer that points at the start of the last completed

channel scan. This can be used to provide a real- time display for a background

operation.

Data[CurIndex] points to the start of the last complete channel scan that

was put in or taken out of the buffer. You should expect

CurIndex to increment by

the number of channels in the scan as well. If no points in the buffer have been

accessed yet then

CurIndex will equal -1. This value can also behave differently in

cases where

CONTINUOUS and BACKGROUND options are both set (see CurCount

description). Refer to board-specific information for details.

If you use the

CONVERTDATA option with either the CONTINUOUS option or with pre-

triggering functions then

CurIndex will return the index of the last A/D sample,

rather than the start of the last completed channel scan.

For many background operations

CurCount = CurIndex. For pre-trigger inputs

though, they are different. If the hardware allows background trigger operations,

CurCount indicates how many points of the TotalCount have been collected.

CurCount will rise to PreTrigCount, stop until the trigger occurs then rise to

TotalCount. CurIndex though will constantly increase and reset as it goes around

and around the circular buffer while waiting for the trigger to occur.

Data Array of acquired data or output data, depending on the background operation.

CurCount and CurIndex refer to this array.

ErrCode Error code returned from the Universal Library. Zero if no error occurred. Use the

ErrMsg VI to convert

ErrCode into a readable string.

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