C-20
DriverLINX Configuration Notes
If you select the ±5V range, the D/A output range will be from -5 to +5V
as follows:
D/A Conversion Delay
The DAS-1800ST/HR and the other DAS-1800 models cannot support
direct hardware timing of D/A output. D/A conversions are timed using
either software polling of the analog input counter/timer or interrupts
from A/D end-of-conversion signal. Either technique requires software to
update the hardware registers with new values as rapidly as possible after
a clock event occurs. Variations in interrupt latencies and bus timing will
add noticeable jitter to D/A signals output at high rates. You should run
empirical tests to determine suitability of D/A output for the intended
purpose.
The DAS-1800AO has a dedicated counter/timer for analog output, which
provides the ability to pace D/A conversions in hardware. This board
supports Polled, Interrupt, and DMA modes of data transfer. Minimum
conversion delay is primarily a function of the D/A mode selected and
operating parameters of other active tasks, if any. The DAC hardware is
capable of converting data at 500kHz. It will run at that rate under
Windows with DriverLINX if the D/A task runs alone or in the recycle
mode with an active analog input task. On a typical 486DX2/66-based
computer, running in the synchronous analog input/output mode, a
100kHz rate for each task is easily attainable without degrading overall
system performance. If both AI and AO tasks use DMA (different
channels), 200kHz for each is achievable, but system response noticeably
slows.
Table C-7. Binary Values and D/A Voltage
Binary Value
D/A Output Voltage
-2048 -5.0000V
0 0.0000V
1 +2.4414mV
+2047 +4.9976V
Voltage Resolution
10V
4096
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2.4414mV
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