Chapter 3: Architecture
22
Note The quad output DACs has current limitations. Only
one output of each quad can be continuously shorted to
ground. Two, three and even four channels shorted to ground
MUST NOT exceed five seconds.
Analog Output Mode
Single Update
The PowerDAQ AO boards operate with either a single-
update or streaming (waveform) output configuration.
Single-update mode allows direct write access to any of the
16-bit DACs of the PowerDAQ AO board. The update
frequency is at least 1kHz for the single update mode and
can be as high as 15KHz in real-time operating
environments. The single update speed is dependent on your
PC system speed.
Note There is a special sub-mode of the single update mode
when all or selected DAC’s outputs are updated
simultaneously.
Event-based Waveform
Event-based waveform mode allows continuous waveform
generation and is not limited by the amount of data. Each
time the DSP based FIFO is ½ full an interrupt is fired to
request additional data to be sent to the board. The
PowerDAQ advanced buffering mechanism hides those
interrupts from the user and allows you to work with big
output arrays logically divided by frames. The end of each
frame can generate an event, which will request more data
from the application. Complete information on the
PowerDAQ advanced circular buffer (ACB) can be found at
www.POwerDAQ.com
Note If the on-board FIFO is empty or the last value is
outputted, the board will continue outputting the last DC
value.
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