Manual PCI-DA12-2/4/6
5
Chapter 1: Introduction
Features
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2, 4, or 6 Channels of Analog Output, 12 Bits Resolution.
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16 Digital I/O Lines Buffered on the Card.
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Digital I/O Buffers Can Be Tri-stated under Program Control.
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Pull-Ups on Digital I/O Lines.
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Resettable fused +5V and +12V supplies available, 0.5A at Room Temperature.
Description
The card is a half-size card that can be installed in any PCI slot of PC-AT class computers. It contains
two, four, or six double-buffered digital-to-analog converters (DACs) that provide independent analog
output channels of 12-bit resolution. Each analog output channel can be configured for ranges of:
0V to +2.5V
0V to +5V
0V to +10V
-2.5V to +2.5V
-5V to +5V
-10V to +10V
4mA to 20mA
The analog output channels have a double-buffered input for single-step update and each is addressed at
its own I/O location. Type AD7237 double-buffered, dual, DAC chips are used. The analog outputs can be
updated either independently or simultaneously.
The DAC outputs are undefined at power-up. Therefore, in order to prevent excessive outputs to external
circuits, the card contains automatic circuits that set D/A outputs to less than 15 percent of span at
system power-on. Upon power-up, the card is in the Simultaneous Update mode. After all DACs have
been loaded with the desired values, a software command can be used to switch the reference voltage to
its normal value. Similarly, a software command can be used at any time to set the reference voltage to
15 percent causing all DAC outputs to be equal to 15 percent of each DACs programmed value.
Each I/O line is buffered by a type 74ABT245B tristate buffer transceiver capable of sourcing 32 mA or
sinking 64mA. Pull-ups on the card assure that there are no erroneous outputs at power up. The lines
initialize in the input mode, the buffers are configured by hardware logic for input or output according to
direction assignment from a control register in the PPI.
