User`s guide

Operation Theory • 45
4.2.2.2 Iterative Waveform Generation
Set IC_Counter in order to generate iterative waveforms from the data of a
single waveform. The counter stores the iteration number, and the itera-
tions could be finite (Figure 26) or infinite(Figure 27). Note that in infinite
mode the waveform generation won’t stop until software stop function is
executed, and IC_Counter is still meaningful when stop mode III is
selected. Please refer to 4.2.2.3 for details.
A data FIFO on board is used to buffer the digital data for DA output. If the
data size of a single waveform specified (That is, Update Counts in
UC_Counter) is less than the FIFO size, after initially transferring the data
from host PC memory to the FIFO on board, the data in FIFO will be
automatically re-transmitted whenever a single waveform is completed.
Therefore, it won’t occupy the PCI bandwidth when the iterative waveforms
are performed. However, if the data size of a single waveform specified is
more than the FIFO size, it needs to intermittently perform DMA to transfer
data from host PC memory to the FIFO on board when the iterative
waveforms are performed and occupies PCI bandwidth. The data FIFO
size on the DAQ/PXI-22XX is 1024(words) when one DA channel is en-
abled, and 512(words) when both DA channels are enabled.
(UC _Counter=4, IC_Counter=3)
4 update counts, 3 iterations
DAWR
WFG_in_progress
Operation start
Trigger
Output Waveform
0
2
4
A single waveform
Figure 26: Finite iterative waveform generation with Post-trigger
and DLY2_Counter = 0
(Assuming the data in the data buffer are 2V, 4V, 2V, 0V)