Manual PCI-A12-16A
6
Discrete Digital I/O
24 bits of TTL/CMOS compatible digital I/O capability are provided. The 24 bits of digital output are controlled
by an 8255-style programmable peripheral interface chip. These 24 bits are arranged into three 8-bit ports,
which can be independently programmed to be inputs or outputs. One of the ports (Port C) may be split into
two 4-bit ports.
These 24 bits are available on a separate 50 Pin header and are buffered. A fused +5 VDC is also available
on Pin 49 of that header.
Counter/Timer
This card contains a type 8254 counter/timer that has three 16-bit programmable down counters.
Counter/Timer 0 is enabled by a pin on the connector (CTR0) and uses an external clock of up to 10 MHz as
selected by user software. Counter/Timers 1 and 2 are concatenated to form a 32-bit counter and receive 1
MHz clock inputs from an on-board crystal-controlled oscillator.
The counter/timers can be set up for event counting, frequency or period measurements, and pulse or wave
form generation. Also, Counter/Timers 1 and 2 can be programmed to initiate A/D conversions. A driver with
source code is provided to facilitate use of the counter/timer chip in data acquisition applications.
Analog Outputs
Two digital-to-analog converters are provided. They are controlled by an AD7237 dual DAC. They are
independently configurable by means of on-board switches. Each may be configured to unipolar or bipolar
outputs and may have full-scale ranges of 2.5, 5, or 10 volts.
Interrupts
This card has interrupt capability within the PCI bus. The interrupt for the card can be software enabled and
can be initiated by various FIFO status conditions.
Transferring Data into the Computer
This card has been designed to provide high data throughput using the PCI bus. Direct I/O transfers provide
the easiest means of transferring the data to memory. This type of transfer allows data to be sent at rates of
over 100,000 samples per second.
Also, program transfers are subject to disruption by other interrupt processes in the computer. Use of real
time triggering of the A/D assures synchronized sampling that is unaffected by other computer operations.
That capability is essential in applications such as signal analysis, fast Fourier transform, and vibration and
transient analysis where high data rates must be sustained for short intervals of time. The FIFO on the card
allows it to acquire data from a list of channels using a point-list FIFO and to store the data in the onboard
data FIFO, eliminating most timing concerns.
Reference Voltage and Power Required
A ±10V (±0.25) reference voltage is available from the A/D reference source for external use. This reference
output can source up to 200 mA of current. The card requires only +5VDC and ±12VDC from the computer
power supply.
