User manual

Page 1-1
Manual MPCI-DA12-16.Dh
Chapter 1: Introduction
Features
• 8 or 16 Channels of Analog Output, 12 Bits Resolution.
• 24 Digital I/O Lines Buffered on the Card.
• Digital I/O Buffers Can Be Tri-stated under Program Control.
• Four and Eight Bit Ports Independently Selectable for Input or Output.
• Pull-Ups on Digital I/O Lines.
• Resettable fused +5V Supply Available to the User.
• Three 16-bit 1MHz down-counters, can generate interrupts to clock DACs.
Description
The PCI-DA12-8/16 are full-size cards that can be installed in any long PCI slot of PC-AT class
computers. They contain either eight or sixteen 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 sink
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. Data are
transferred into outer registers a byte at a time and then transferred into inner registers a word at a
time. The analog outputs can be updated either independently, simultaneously by command, or
simultaneously by timer.
The DAC outputs are undefined at power-up. Therefore, in order to prevent excessive outputs to
external circuits, PCI-DA12-8/16 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 not 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
DAC’s programmed value.
These cards contain a type 8255-5 Programmable Peripheral Interface (PPI) chip providing 24 bits
of parallel digital input/output. They can be programmed to accept inputs or to provide outputs on
three 8-bit ports designated Ports A, B, and C. Port C can be further divided into two 4-bit nibbles.