VXI VT1433B, Руководство пользователя, Страница: 103 / 203

Limit on Queuing of Data
In overlap block mode, a number of trigger events may be queued up before the
host reads the data for those triggers. The host may get further and further behind
the data acquisition.
However, if the host gets far enough behind that the FIFO fills up, data
acquisition must momentarily stop and wait for data to get transferred to the host.
This places a limit on how far in time the host can be behind the data
acquisition. By setting the size of the FIFO, it is possible to control how far
behind the host can get.
Making Overlap Block Mode Act Like Traditional Block Mode
If the FIFO size is set the same as the block size or if the number of pending
triggers is limited to zero, then overlap block mode becomes identical to
traditional block mode.
Making Overlap Block Act Like Continuous Mode
If the module is in auto-arm and auto-trigger mode, then overlap block mode
becomes nearly the same as continuous mode.
One difference is that traditional continuous mode has a single arm and trigger,
while overlap block mode may have multiple arms and triggers. Another is that
continuous mode can be configured to start at any type of trigger event, while
overlap block mode must be in auto-trigger mode to act like continuous mode.
Finally, continuous mode always stops when a FIFO overflow occurs, but overlap
block mode does not.
VT1433B User's Guide
The Host Interface Library
4-25