C-16
DriverLINX Configuration Notes
The DAS-1800AO models offer two channels of multiplying 12-bit D/A
converters that support DMA mode of data transfer at continuous output
rates of up to 500kHz. A 2K sample FIFO buffer allows continuous,
gap-free data transfer for data buffers larger than 2K. Alternatively, for
data buffers smaller than 2K samples, the AO task can “free-run” entirely
from the on-board DAC FIFO buffer using the board’s recycle mode.
For the DAS-AO hardware, DriverLINX can automatically promote AO
tasks meeting the following criteria as specified in the Service Request to
run from the DAC FIFO buffer in recycle mode:
Mode = INTERRUPT
Stop Event type = COMMAND
Notify flag (in buffer list) = FALSE
Data buffer samples < 2048
The advantages of using the DAC FIFO buffer for free-run, recycle mode
analog output are:
●
Traffic on the memory bus is significantly reduced at high output
rates.
●
The system response latency will be noticeably shortened.
●
The analog output timing will be immune to traffic on the memory
and I/O buses.
The disadvantages are:
●
You cannot change the analog output values while the analog output
task is running.
●
There is a delay while DriverLINX loads the FIFO.
●
Buffer-filled notification messages cannot be posted as the hardware
does not permit detection of end-of-buffer conditions.
●
The
STATUS
operation cannot provide the “number of buffers
processed” report.
You can disable automatic promotion to recycle mode by DriverLINX.
This forces all AO tasks to run from computer memory instead of the
DAC FIFO. See “Special Device Settings” on page C-4.
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