OVERVIEW The
PCM-AIO is a multipurpose 12-bit analog input and
analog output module. It can serve as a data acquisition
and control board for use with PC/104 compatible
embedded systems. The analog input is software configurable
with either single-ended or differential inputs.
Any channel can be configured as unipolar or bipolar
for maximum flexibility.
The PCM-AIO module can be ordered without the D/A
circuitry to yield the lowest cost A/D function.
The PCM-AIO module also provides two, independent
12-bit analog voltage output channels. Each channel
can be configured for one of 2 ranges. Both channels
are double buffered and operate in simultaneous update
mode.
FUNCTIONAL CAPABILITY PC/104 Interface - The PCM-AIO is I/O port mapped
and requires 12 contiguous addresses.
Analog to Digital Converter -
The PCM-AIO uses the Maxim MAX180, 12-bit data acquisition
chip. It combines
an 8 channel input multiplexer, high bandwidth
Track-and-Hold (T/H), low-drift zener reference, and
flexible microprocessor interface with a high conversion
speed, successive approximation analog to digital
converter. The device samples and digitizes in ten
microseconds.
The MAX180 can be software configured for unipolar
or bipolar operation and single-ended or differential
inputs on a per channel basis. Output coding is natural
binary for unipolar operation with 1 LSB = 1.22mV
(5V/4096). Coding is twos complement for bipolar. Potentiometers
are on the card to permit both gain and
offset adjustment.
Starting a Conversion - The
conversion is begun by writing a word to the control register
to select the
channel and specify if it is single-ended/differential
and unipolar/bipolar. Output data is latched and the
PCM-AIO sets a Busy flag signaling conversion complete.
An interrupt request is also generated after each
completed conversion. A jumper selects IRQ2 through
IRQ7 on the PC/104 bus.
Input Configuration - Each
A/D channel is input from a single 26-pin connector. WinSystems
offers the
CBL-120-3 which is a 3 foot, #28 AWG, ribbon cable
designed to provide access to signals from the 26-pin,
0.100" grid connector on the PCM-AIO.
Also available is the CBL-130-4, a 4 foot, ribbon cable,
that will connect the PCM-AIO to the Analog-ADP. The
Analog-ADP is a non-isolated signal conditioner and termination
panel of analog signals for use with
WinSystems' A/D converters.
Digital to Analog Converter -
The PCM-AIO contains an Analog Devices' AD7537. Two
independent 12-bit DACs are on one monolithic chip and configured
to
provide either unipolar or bipolar outputs. The output range
is 0 to +5 or ±5 volts.
A two-byte
I/O write is required to update the 12-bit
D/A. The digital data input section is double buffered
to allow simultaneous update of both DAC's. These
registers latch the 12-bit digital word and keeps the D/A
converter's output constant until it is updated with
a
new value in one step.
Output Configuration - The D/A output channels are
wired to a 26-pin connector. Alternating ground lines,
paired with each output channel's signal lines improves
noise immunity and reduces cross talk.
SPECIFICATIONS Electrical A/D Section
Number of Channels: Up to 8
A/D Resolution: 12-bits
Input range: 0 to +5 volts; single-ended
-2.5 to +2.5 volts; differential
Coding: Natural binary (unipolar)
Two's complement (bipolar)
Nonlinearity: ±1 LSB
Gain error: Adjustable to zero
Conversion speed: 10 microseconds
Electrical
D/A Section
Number of Channels: 2
D/A Resolution: 12-bits
Coding: Straight binary (unipolar)
Offset binary (bipolar)
Output Voltage Range: 0 to +5V; ±5V @5 mA
Nonlinearity: ±1 LSB
Relative Accuracy: ±1 LSB
Output Settling Time: 5 uS Electrical Power Requirements
+5 VDC ±5% at 30 mA (typ.)
-12VDC ±10% at 25 mA (typ.)
Mechanical
Dimensions: 3.6" x 3.8" (90mm x 96mm)
Connectors A/D Input: 26-pin dual on 0.100" grid
D/A Output: 26-pin dual on 0.100" grid
Environmental
Operational Temperature: 0°C to +65°C
