ADLINK PXI-2208 - Manual (Page 72)

60 Operation Theory
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 iterations may be finite (Figure 4-18) or infinite
(Figure 4-19). Take note that in infinite mode the waveform
generation does not stop until software stop function is exe-
cuted and IC_Counter is still valid when stop mode III is
selected. Both figures assume that the data in the data buffer
are 2V, 4V, 2V, and 0V.
An onboard data FIFO is used to buffer the digital data for DA
output. If the data size of a single waveform you specified (That
is, Update Counts in UC_counter) is less than the FIFO size,
after initially transferring the data from the host PC memory to
the FIFO on board, the data in the FIFO will be automatically
re-transmitted whenever a single waveform is completed.
Therefore, it does not occupy the PCI bandwidth when repeti-
tive waveforms are performed. However, if the size of a single
waveform were larger than that of the FIFO, it needs to be
intermittently loaded from the host PC’s memory via DMA,
when a repetitive waveforms is performed thus PCI bandwidth
would be occupied.
The data FIFO size on the DAQ-/DAQe-/PXI-2204/2205/2206/
2208 card is 1024 (words) when one DA channel is enabled, or
512 (words) when both DA channels are enabled.
Figure 4-18: Finite Iterative Waveform Generation with Post-trigger
(DLY2_Counter = 0)