Measurement Computing ADAC-LVi - Manual (Page 75)

Chapter 2 Digital I/O VIs
ADAC LabVIEW VI 69
ADAC DIO Read
This VI reads data from an queued DIO buffer and returns the data acquired in binary
data units.
The BUFFER STATUS cluster is useful in determining the current status of the
acquisition by presenting the Buffer DoneFlag, StatusFlag and ErrorFlag conditions as
described below. The BUFFER STATUS is especially useful in multi-
buffered/continuous acquisition where no interaction takes place except from incoming
buffers.
Before reading any data, DIO Read checks to see if the input cluster error in indicates
that an error has already occurred. If so, this VI does not read any data, but passes the
error information unmodified through error out.
Device Handle (0) Device Handle is a numeric value that identifies the board's DIO
subsystem to be acted upon. The default Device Handle is 0.
Buffer Number (-1:next) Buffer Number is the ID number of the buffer to be obtained.
The Buffers are numbered from 0-n as specified in the ADAC DIO Config VI. The
default input is -1, which tells ADAC-LVi to return the next available buffer in the done
queue. For multi-buffered or continuous acquisitions, setting Buffer Number to -1
provides the easiest method of obtaining the next buffer available in the done queue.
Queued buffers are returned in a first done first available fashion.
Number of Scans to Read (-1:all) Number of Scans to Read specifies the number of
scans the VI retrieves from the acquisition buffer. The default input is -1, which tells
LabVIEW to set number of scans to read equal to the value of the DAQ buffer size. Once
a buffer is successfully read into LabView the buffer is placed back into the device's
available buffer queue. If the Number of Scans to Read is less than the actual buffer size,
all unread data will be lost.
Time Limit in Seconds (1.00) Time Limit in Seconds specifies the maximum length of
time this VI waits for a done buffer. You express time limit in seconds. If this VI does
not receive a completed buffer status prior to the timeout period, the VI returns an error.
error in (no error) Error in describes error conditions occurring before this VI executes.
This cluster defaults to no error.