National Instruments 321645c-01 用户手册
Chapter 2
Function Reference — WFM_Load
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National Instruments Corporation
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NI-DAQ FRM for PC Compatibles
Note
The following information applies to DAQArb 5411 devices only:
iterations is the number of times the waveform generation steps through buffer. A value of
0 means that waveform generation proceeds indefinitely.
Range:
0 means that waveform generation proceeds indefinitely.
Range:
0 through 2
32
– 1.
Enabling FIFO mode waveform generation places some restrictions on the allowable values
for the iterations parameter. Refer to the mode parameter description below.
for the iterations parameter. Refer to the mode parameter description below.
Enabling pulsed FIFO mode waveform generation by turning on the delay clock via
WFM_ClockRate
places two additional restrictions on the allowed values of iterations and
also changes its meaning. Setting iterations to 0 is not allowed. Setting iterations to 1 is not
allowed if you are using an AT-MIO-16X or AT-MIO-64F-5. Also, instead of determining the
number of times the waveform generation steps through buffer before stopping, pulsed FIFO
mode causes the iterations setting to determine the number of times the data in the FIFO is
generated before pausing for the specified delay. Once the delay has elapsed, the data in the
FIFO is generated again. In other words, when you use pulsed FIFO mode, the value of
iterations determines the number of cycles through the FIFO that occurs between delays,
allowed if you are using an AT-MIO-16X or AT-MIO-64F-5. Also, instead of determining the
number of times the waveform generation steps through buffer before stopping, pulsed FIFO
mode causes the iterations setting to determine the number of times the data in the FIFO is
generated before pausing for the specified delay. Once the delay has elapsed, the data in the
FIFO is generated again. In other words, when you use pulsed FIFO mode, the value of
iterations determines the number of cycles through the FIFO that occurs between delays,
Table 2-40. Mode Values for the Count Parameter for DAQArb 5411 Devices
Mode
Count
0
not supported
1
Minimum count is 256 samples. Must be a multiple of 8 samples.
Maximum count = size of the memory; that is, if memory size = 2 MB,
maximum number of samples = 2,000,000.
Maximum count = size of the memory; that is, if memory size = 2 MB,
maximum number of samples = 2,000,000.
2
Must be equal to 16,384 samples. If you load less samples, you will see
the contents of unfilled sections of memory also appearing in the
waveform generation in this mode.
the contents of unfilled sections of memory also appearing in the
waveform generation in this mode.
3
Minimum count = 256 samples. Must be a multiple of 8 samples.
Maximum number of samples depends on the number of times you have
called
Maximum number of samples depends on the number of times you have
called
WFM_Load
consecutively in this mode. The total of all counts
loaded should be less than or equal to the size of the memory. If memory
size = 2 MB, it should be less than or equal to 2,000,000.
size = 2 MB, it should be less than or equal to 2,000,000.
4
The count depends on the number of stages being loaded. Because this
mode is valid only after you have called
mode is valid only after you have called
WFM_Load
with mode 2 or
mode 3, the maximum number of stages depend on the mode that was
called earlier.
called earlier.
Maximum count occurs when:
mode 2 was called earlier = 340 stages
mode 3 was called earlier = 290 stages
mode 2 was called earlier = 340 stages
mode 3 was called earlier = 290 stages