Acces I/O products PCI-A12-16A User manual

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10623 Roselle Street, San Diego, CA 92121 • [phone] • FAX [phone]
[email protected] • www.accesio.com
MODEL PCI-A12-16A
USER MANUAL
FILE: MPCI-A12-16A.A1o

Manual PCI-A12-16A
2
Notice
The information in this document is provided for reference only. ACCES does not assume any liability arising
out of the application or use of the information or products described herein. This document may contain or
reference information and products protected by copyrights or patents and does not convey any license under
the patent rights of ACCES, nor the rights of others.
IBM PC, PC/XT, and PC/AT are registered trademarks of the International Business Machines Corporation.
Printed in USA. Copyright 2004, 2006 by ACCES I/O Products Inc, 10623 Roselle Street, San Diego, CA
92121. All rights reserved.
WARNING!!
ALWAYS CONNECT AND DISCONNECT YOUR FIELD CABLING WITH
THE COMPUTER POWER OFF. ALWAYS TURN COMPUTER POWER OFF
BEFORE INSTALLING A CARD. CONNECTING AND DISCONNECTING
CABLES, OR INSTALLING CARDS INTO A SYSTEM WITH THE
COMPUTER OR FIELD POWER ON MAY CAUSE DAMAGE TO THE I/O
CARD AND WILL VOID ALL WARRANTIES, IMPLIED OR EXPRESSED.

Manual PCI-A12-16A
3
Warranty
Prior to shipment, ACCES equipment is thoroughly inspected and tested to applicable specifications.
However, should equipment failure occur, ACCES assures its customers that prompt service and support will
be available. All equipment originally manufactured by ACCES which is found to be defective will be repaired
or replaced subject to the following considerations.
Terms and Conditions
If a unit is suspected of failure, contact ACCES' Customer Service department. Be prepared to give the unit
model number, serial number, and a description of the failure symptom(s). We may suggest some simple
tests to confirm the failure. We will assign a Return Material Authorization (RMA) number which must appear
on the outer label of the return package. All units/components should be properly packed for handling and
returned with freight prepaid to the ACCES designated Service Center, and will be returned to the
customer's/user's site freight prepaid and invoiced.
Coverage
First Three Years: Returned unit/part will be repaired and/or replaced at ACCES option with no charge for
labor or parts not excluded by warranty. Warranty commences with equipment shipment.
Following Years: Throughout your equipment's lifetime, ACCES stands ready to provide on-site or in-plant
service at reasonable rates similar to those of other manufacturers in the industry.
Equipment Not Manufactured by ACCES
Equipment provided but not manufactured by ACCES is warranted and will be repaired according to the terms
and conditions of the respective equipment manufacturer's warranty.
General
Under this Warranty, liability of ACCES is limited to replacing, repairing or issuing credit (at ACCES
discretion) for any products which are proved to be defective during the warranty period. In no case is ACCES
liable for consequential or special damage arriving from use or misuse of our product. The customer is
responsible for all charges caused by modifications or additions to ACCES equipment not approved in writing
by ACCES or, if in ACCES opinion the equipment has been subjected to abnormal use. "Abnormal use" for
purposes of this warranty is defined as any use to which the equipment is exposed other than that use
specified or intended as evidenced by purchase or sales representation. Other than the above, no other
warranty, expressed or implied, shall apply to any and all such equipment furnished or sold by ACCES.

Manual PCI-A12-16A
4
Table of Contents
Chapter 1: Introduction .................................................................................................................................... 5
Description.................................................................................................................................................... 5
Input System Expansion.............................................................................................................................. 5
Discrete Digital I/O........................................................................................................................................ 6
Counter/Timer ............................................................................................................................................... 6
Analog Outputs............................................................................................................................................. 6
Interrupts....................................................................................................................................................... 6
Transferring Data into the Computer.......................................................................................................... 6
Reference Voltage and Power Required .................................................................................................... 6
Specifications................................................................................................................................................ 7
Figure 1-1: Block Diagram......................................................................................................................... 9
Chapter 2: Installation .................................................................................................................................... 10
Configure Card Options via Jumper Selection........................................................................................ 10
CD Software Installation ............................................................................................................................ 10
WINDOWS ............................................................................................................................................... 10
LINUX....................................................................................................................................................... 10
Hardware Installation ................................................................................................................................. 11
Chapter 3: Option Selection........................................................................................................................... 12
Figure 3-1: Option Selection Map............................................................................................................ 13
Chapter 4: Address Selection........................................................................................................................ 14
Chapter 5: Programming................................................................................................................................15
Table 5-1: Register addresses on the card (hex).................................................................................... 15
Register Descriptions................................................................................................................................. 16
Software Tristate Mode.............................................................................................................................. 20
Programming Guide................................................................................................................................... 21
Chapter 6: Programmable Interval Timer ..................................................................................................... 24
Operational Modes ..................................................................................................................................... 24
Programming............................................................................................................................................... 26
Programming Examples............................................................................................................................. 29
Chapter 7: Calibration..................................................................................................................................... 31
Chapter 8: Connector Pin Assignments....................................................................................................... 32
Table 8-1: Analog Connector Pin Assignments....................................................................................... 32
Table 8-2: Digital Connector Pin Assignments........................................................................................ 33
Customer Comments...................................................................................................................................... 34

Manual PCI-A12-16A
5
Chapter 1: Introduction
The card is a multifunction high-speed analog-to-digital converter card for use in 5-volt and 3.3-volt PCI bus
computer slots. With this card installed the computer can be used as a precision data acquisition and control
system or as a signal analysis instrument.
Description
The card accepts up to eight differential or 16 single-ended analog input channels. Inputs are protected
against over-voltage conditions up to +35 volts and typically survive static discharges beyond 4000 volts. The
channel input configuration is software selectable. When using the card in differential mode the common
mode rejection ratio is a minimum 80dB at 45KHz and the common mode voltage rejection capability is +11V.
The input signals are amplified by an onboard instrumentation amplifier to provide voltage ranges of 10, 5,
1.25-6.25, and 1.25-3.75 volts unipolar and ±10, ±5, ±2.5 and ±1.25 volts bipolar. In addition, you can read 4-
20 mA current inputs by manually installing jumpers to utilize onboard resistors. In this case, the current input
is converted to an analog voltage range of 1.25-6.25V with full 12-bit resolution and there can be up to eight
inputs. Each channel must be dedicated to either voltage or current.
This card contains an industry standard 12-bit successive-approximation analog-to-digital converter (A/D) with
a sample and hold amplifier input. Under ideal conditions throughput of over 100,000 conversions per second
is possible.
This card has a 4k samples FIFO data buffer and a 4k words point list buffer. These buffers give capability for
full-speed counter-driven background data-acquisition with no computer interaction until the data FIFO needs
draining. This allows 100kHz data to be taken with little processor overhead.
A/D conversions may be initiated in any of three ways: (a) software command, (b) an on-board programmable
timer, or (c) direct external trigger. In turn, data may be transferred to the computer by any of three software
selectable methods: (a) polling for end-of-conversion (EOC), (b) polling for a half-full FIFO, or (c) a half-FIFO
interrupt.
Input System Expansion
This card can be used with up to 16 external AIM-16P analog input expansion cards. Each AIM-16P card
provides capability for 16 differential inputs and thus can be used to provide a maximum of 256 analog inputs
per combination of analog input expansion cards and a single A12-16A. The initial AIM-16Ps are connected to
the card by a special cable adapter and ribbon cable. Additional AIM-16P units are connected by daisy-
chaining with ribbon cables. In the normal system configuration each AIM-16P is connected to a single-ended
input of this card. However, if interconnection cable noise becomes problematic or if long cables are required,
then the AIM-16P cards can be connected to the differential inputs of the card. Using the differential
connection allows better monitoring of remote locations because noise will be reduced by the common mode
noise rejection capability of the card. (Note: In this configuration, the maximum number of inputs that can be
handled is 128.)
Note: If the VRef from the card is to be used to power a bridge or other apparatus connected to the AIM-16,
then pin 28 on J1 of the the card must be grounded. Consult the factory to obtain a specially modified card
that implements this option.
The control register at base address+3 provides channel and gain control bits for use with submultiplexers
like the AIM-16. SEL3-SEL0 are typically used for channel, and G2-G0 are used for gain. If no submulitplexer
is being used, it is a good idea to use SEL3-SEL0 as ID tags. These values will comprise the top four bits of
the data returned from the A/D converter.

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.

Manual PCI-A12-16A
7
Specifications
A/D Specification
• Type: Successive approximation.
• Resolution: 12 binary bits.
• Conversion Time: 8 µsec max., 5.7 µsec typical.
• Integral Linearity Error: ±0.45 LSB maximum.
• Differential Non-Linearity: No missing codes.
• Monotonicity: Guaranteed over operating temperature range.
• Linearity: ±1 bit.
• Zero Drift: ±10 ppm/°C maximum.
• Gain Drift: ±45 ppm/°C maximum.
• Trigger Source: Software selectable, external trigger, programmable timer, or
program command.
Sample and Hold Amplifier
• Acquisition Time: 1 microsecond to 0.01% typical for full scale step function
input.
• Aperture Uncertainty: 0.3 nanosecond typical.
Reference Voltage Output
• Voltage: +10VDC ±0.25VDC.
• Temp. Coefficient: ±30 ppm/°C.
• Load Drive: 200mA maximum.
Digital I/O
Inputs
• Logic high: 2.0 to 5.0 VDC at 20 uA maximum at 2.7V.
• Logic low: -0.5 to +0.8 VDC at -0.4mA maximum.
Output
• Drivers are 74ABT245s.
• Logic High: 2.0 VDC min., -32mA.
• Logic Low: 0.5 VDC max., 64mA.
• Power Output: +5 VDC from computer bus (onboard resettable 0.5A fuse).

Manual PCI-A12-16A
8
D/A Specification
• Type: AD7237, Dual 12-Bit D/A’s with 12 bit resolution.
• Output ranges: 0-2.5, 0-5, 0-10, ±2.5, ±5 and ±10 volts are selectable.
• Load Drive: ±15mA maximum per output.
Programmable Timer
• Type: 82C54-2 programmable interval timer.
• Counters: Three 16-bit down counters, two permanently concatenated
with 1MHz clock as programmable timer.
• Output Drive: 2.2mA at 0.45V (5 LSTTL loads).
• Input Gate: TTL/DTL/CMOS compatible.
• Clock Frequency: DC to 10MHz.
• Active Count Edge: Negative edge.
• Min Clock Pulse Width: 30nS high/50nS low.
• Timer Range: 2.5 MHz to <1 pulse/hr.
Environmental
• Operating Temp: 0 °C. to 50 °C.
• Storage Temp: -20 °C. to +70 °C.
• Humidity: 0 to 90% RH, non-condensing.
• Power Required: +5VDC: 600 mA typical.
+12VDC: 650 mA typical.
-12VDC: 650 mA typical.

Manual PCI-A12-16A
9
16 S.E./
8 DIFF'L
SWITCH
UNI
BIP
UNIPOLAR/
BIPOLAR
SELECT
SAMPLE/
HOLD 12 BIT A/D CONVERTER
A/D & MUX
DATA REGISTER
STATUS
REGISTER
MUX INCREMENT
& CONTROL LOGIC
MUX
VREF
16 S.E.
OR
8 DIFF'L
A
NALO
G
INPUTS
DATA
BUFFERS
ADDRESS
DECODE
SELECT
&
CONTROL
REGISTER
INTERRUPT
CONTROL
TRIGGER
SELECT
LOGIC
DAC 0
AND
DAC 1
7 BIT
OUTPUT
REGISTER
(SUBMUX
CONTROL)
1
2
4
8GAIN
SELECT
INTERNAL DATA BUS
I
B
M
P
C
I
B
U
S
A/D TRIG
DAC 0
GN0
GN1
GN2
SEL0
SEL1
SEL2
SEL3
DAC 1
CH0 HI
CH0 LO
CH15
16
BIT
CTR
0
16
BIT
CTR
1
16
BIT
CTR
2
1MHz
XTAL
CTR0
CLOCK
IN
CTR2
OUT
IIIGGG
OOO
8255
DIGITAL
INPUT /
OUTPUT
INTERFACE
24 BITS
TTL
DIGITAL
I/O
DIO0
DIO23
Figure 1-1: Block Diagram

Manual PCI-A12-16A
10
Chapter 2: Installation
A printed Quick-Start Guide (QSG) is packed with the card for your convenience. If you’ve already performed
the steps from the QSG, you may find this chapter to be redundant and may skip forward to begin developing
your application.
The software provided with this card is on CD and must be installed onto your hard disk prior to use. To do
this, perform the following steps as appropriate for your operating system.
Configure Card Options via Jumper Selection
Before installing the card into your computer, carefully read Chapter 3: Option Selection of this manual, then
configure the card according to your requirements. Our Windows based setup program can be used in
conjunction with Chapter 3 to assist in configuring jumpers on the card, as well as provide additional
descriptions for usage of the various card options.
CD Software Installation
The following instructions assume the CD-ROM drive is drive “D”. Please substitute the appropriate drive
letter for your system as necessary.
WINDOWS
1. Place the CD into your CD-ROM drive.
2. The system should automatically run the install program. If the install program does not run promptly,
click START | RUN and type BGLQR?JJ, click OK or press -.
3. Follow the on-screen prompts to install the software for this board.
LINUX
1. Please refer to linux.htm on the CD-ROM for information on installing under linux.
Caution! * ESDA single static discharge can damage your card and cause premature failure!
Please follow all reasonable precautions to prevent a static discharge
such as grounding yourself by touching any grounded surface prior to
touching the card.

Manual PCI-A12-16A
11
Hardware Installation
1. Make sure to set switches and jumpers from either the Option Selection section of this manual or
from the suggestions of SETUP.EXE.
2. Do not install card into the computer until the software has been fully installed.
3. Turn OFF computer power AND unplug AC power from the system.
4. Remove the computer cover.
5. Carefully install the card in an available 5V or 3.3V PCI expansion slot (you may need to remove a
backplate first).
6. Inspect for proper fit of the card and tighten screws. Make sure that the card mounting bracket is
properly screwed into place and that there is a positive chassis ground.
7. Install an I/O cable onto the card’s bracket mounted connector.
8. Replace the computer cover and turn ON the computer which should auto-detect the card (depending
on the operating system) and automatically finish installing the drivers.
9. Run PCIfind.exe to complete installing the card into the registry (for Windows only) and to determine
the assigned resources.
10. Run one of the provided sample programs that was copied to the newly created card directory (from
the CD) to test and validate your installation.
The base address assigned by BIOS or the operating system can change each time new hardware is installed
into or removed from the computer. Please recheck PCIFind or Device Manager if the hardware configuration
is changed. Software you write can automatically determine the base address of the card using a variety of
methods depending on the operating system. In DOS, the PCI\SOURCE directory shows the BIOS calls used
to determine the address and IRQ assigned to installed PCI devices. In Windows, the Windows sample
programs demonstrate querying the registry entries (created by PCIFind and NTIOPCI.SYS during boot-up) to
determine this same information.

Manual PCI-A12-16A
12
Chapter 3: Option Selection
To operate the card in the current mode, install a jumper in the positions shown at CH0 through CH7 for each
channel, 0 to 7 you will be using as a current input. Only differential operation is supported when using current
mode inputs. For best results using 4-20mA inputs, the 1.25-6.25 volt range is recommended.
The Buffer Enable / Buffer Tristate (BEN/BTR) jumper enables or disables software tristating of the digital I/O
bits. Normally, this jumper will be installed in the BEN position. In order to use the software tristate feature,
install this jumper in the BTR position; this will change the behavior of the DIO bits as described in the
Programming chapter.
The range of each DAC is set by a block of switches on the board. The ranges correspond to switch settings
as follows:
Switch
321Range
ON OFF OFF 0-2.5V
OFF OFF OFF 0-5V
OFF ON OFF 0-10V
ON OFF ON ±2.5V
OFF OFF ON ±5V
OFF ON ON ±10V

Manual PCI-A12-16A
13
RP1
RP2
RP3
CH0
CH7
FACTORY
USE
ONLY
SELECT
INPUT
CHANNEL
AS
4-20mA
RP5
RP6
RP7
RP8
BTR BEN
DAC0 DAC1
Pin 1
Figure 3-1: Option Selection Map

Manual PCI-A12-16A
14
Chapter 4: Address Selection
This card uses I/O addresses offset from the base address assigned by the PCI bus. The address spaces are
defined in the programming section of this manual.
PCI architecture is Plug-and-Play. This means that the BIOS or Operating System determines the resources
assigned to PCI cards rather than the user selecting those resources with switches or jumpers. As a result,
you cannot set or change the card's base address or IRQ level. You can only determine what the system has
assigned.
To determine the base address that has been assigned, run the PCIFind utility program. This utility will
display a list of all the cards detected on the PCI bus, the addresses assigned to each function on each of the
cards, and the respective IRQs.
Alternatively, Windows systems can be queried to determine which resources were assigned. In these
operating systems, you can use either PCIFind, or the Device Manager utility from the System Properties
Applet of the control panel. The card is installed in the Data Acquisition class of the Device Manager list.
Selecting the card, clicking Properties, and then selecting the Resources Tab will display a list of the
resources allocated to the card.
The PCI bus supports 64K of I/O address space, so your card's addresses may be located anywhere in the
0000h to FFFFh range.
PCIFind uses the Vendor ID and Device ID to search for your card, then reads the base address and IRQ. If
you want to determine the base address and IRQ without using PCIFind, use the following information:
The Vendor ID for this card is 494F. (ASCII for "IO")
The Device ID for this card is ECAAh.
An example of how to locate PCI card resources is provided with in the PCI\SOURCE directory, under your
installation directory. This code runs in DOS, and uses the PCI defined interrupt BIOS calls to query the PCI
bus for card specific information. You will need the Device ID and Vendor ID listed above to use this code.

Manual PCI-A12-16A
15
Chapter 5: Programming
Offset Write Function Read Function
0 Start Conversion A/D Conversion Data, 8 Least Significant Bits (LSB)
1 unused A/D Conversion Data, 4 Most Significant Bits (MSB)
2 A/D Control (Channel and Range) A/D Control Readback
3 Digital Output / Sub-Mux Control Digital Output Readback
4 Option Control Option Status, Clears Interrupt
5 unused unused
6 unused unused
7 unused unused
8 8254 Counter / Timer 0 8254 Counter / Timer 0
9 8254 Counter / Timer 1 8254 Counter / Timer 1
A 8254 Counter / Timer 2 8254 Counter / Timer 2
B 8254 Counter / Timer Control 8254 Counter / Timer Status
C DAC 0 8 LSB unused
D DAC 0 4 MSB unused
E DAC 1 8 LSB unused
F DAC 1 4 MSB unused
10 8255 Port A Output 8255 Port A Input / Readback
11 8255 Port B Output 8255 Port B Input / Readback
12 8255 Port C Output 8255 Port C Input / Readback
13 8255 Control unused
14 Tristate Enable / Disable unused
Table 5-1: Register addresses on the card (hex)

Manual PCI-A12-16A
16
Register Descriptions
Offset 0 Write Start Conversion
This address is written to if you wish to start a conversion programmatically. Any value written to this address
will cause the A/D to perform a conversion on the currently selected channel at the currently selected range.
Use the A/D Control register at Offset 2 to select the channel and range. Conversions may also be started via
an External Start Conversion signal (pin 4, see Offset 4) or via Counters (see Offset 4).
Offset 1 Write Unused
This address is unused, writes are ignored.
Offset 0 Read A/D Data (Low byte)
Offset 1 Read A/D Data (High nybble + SEL readback)
These addresses allow you to read the data stored in the data FIFO. The data is read oldest to newest. The
values of SEL3-0 are placed in the four most significant bits of Offset 1 and may be used as a data tag.
Since the data is contained in both of these registers, it is a good practice to read Offset 0 and Offset 1 with a
single word read command to assure that the two data registers stay properly synchronized.
Data is presented in two's complement form. The following shows the bit positions of the data returned:
Read as 16-bit integer from Offset 0
Read as byte from Offset 1 Read as byte from Offset 0
sel3 sel2 sel1 sel0 DB DA D9 D8 D7 D6 D5 D4 D3 D2 D1 D0
Read a single 16-bit integer and mask off the high-order 4 bits to obtain a value. See the programming guide
at the end of this chapter for more information.
Sel3 through Sel0 are a readback of the state of the Sel3 through Sel0 bits associated with the point in the
point list FIFO that started the conversion. See Offset 2&3 for an explanation of the Sel bits.
Offset 2&3 Write A/D Control Setup Point List
Offset 2&3 Read A/D Control Readback
This address (base+2) should be written to using a 16-bit WORD command (out dx,ax). Doing so loads the
point-list FIFO. Repeated writes to this address are used to load an entire point-list into the FIFO for later use.
The format of the WORD is described below. After loading up to 4096 WORDS, you must read a WORD from
this address before starting conversions. Refer to the programming guide at the end of this chapter for more
information on using this register.
Note: it is very useful to use SEL3-SEL0 as markers, as long as external muxes are not being used, to track
which channel data is from. When no external mux is being used, writing the same value to SEL3-SEL0 as
MA3-MA0 causes the data FIFO to appear to hold the channel number (MA3-0), which enables easier
tracking of data and channel number.
The following diagrams define bit functions in the point list:
bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0
MA3 MA2 MA1 MA0 DIFF R2 R1 R0
bit 15 bit 14 bit 13 bit 12 bit 11 bit 10 bit 9 bit 8
SEL3 SEL2 SEL1 SEL0 (unused) G2 G1 G0

Manual PCI-A12-16A
17
MA3, MA2, MA1, MA0
These 4 bits form a binary number from 0 to 15. This is the channel number on the A/D board you wish to
setup for conversion. MA3 should be cleared to zero if using Differential mode.
DIFF
This is a control bit for Single-Ended or Differential mode. In Single-Ended mode, the card has 16 channels,
each converted in reference to analog ground. In Differential mode, the card has only 8 channels, and the
conversion returns the voltage difference from the high to the low channel. When the bit is cleared (0), Single-
Ended mode is active; a set bit (1) indicates Differential mode.
R2, R1, R0
These bits select the range at which to convert the data. The following table lists the ranges and the bit
combinations for each range.
R2 R1 R0 Range Code Range
0 0 0 0 bipolar 10 volts, 20 volt span -10 to +10V
0 0 1 1 bipolar 5 volts, 10 volt span -5 to +5V
0 1 0 2 bipolar 2.5 volts, 5 volt span -2.5 to +2.5V
0 1 1 3 bipolar 1.25 volts, 2.5 volt span -1.25 to +1.25V
1 0 0 4 unipolar 10 volts, 10 volt span 0 to 10V
1 0 1 5 unipolar 5 volts, 5 volt span 0 to 5V
1 1 0 6 unipolar 1.25 to 3.75 volts, 2.5 volt span
1 1 1 7 unipolar 1.25 to 6.25 volts*, 5 volt span
*The 1.25-6.25 volt range is designed for use with the Current Mode jumper on each channel. Selecting this
range for those channels that have been placed in current mode results in a 4-20mA range, with full 12-bit
precision.
SEL3, SEL2, SEL1, SEL0, G2, G1, G0
These bits are digital outputs generally used to control channel and gain/range on attached sub-multiplexers
(sub-muxes), such as the AIM-16 or LVDT-8. On our sub-muxes, the SEL bits determine the channel, and the
G bits determine the gain; however, the exact purpose of these bits depends on the sub-mux type used.
Please refer to your sub-mux manual for more information.
The SEL3-0 bits will be returned as the top four bits when the data from the A/D converter is read to the
computer. They may be used to tag the data, if they are not being used for other purposes.
Software may be simplified with a 16-bit “word” write to Base+2, encompassing Base+3 also. That “write”
would look like this:
Base+3 Base+2
bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0
SEL3 SEL2 SEL1 SEL0 X G2 G1 G0 MA3 MA2 MA1 MA0 DIFF R2 R1 R0

Manual PCI-A12-16A
18
Offset 4 Write Option Control
This register is used to control various features on the card.
bit 7 bit 6 bit 5 bit 4 bit 3 Bit 2 bit 1 bit 0
XSCE CCF CF EIFH EIFE CTR
XSCE is External Start Conversion Enable. Setting this bit allows pin 4 on the connector to start conversions.
CCF and CF are Clear Channel FIFO and Clear FIFO (data) respectively. Any time a 1 is written to these bits,
the selected FIFO is reset, effectively clearing its contents.
EIFH set to 1 enables interrupts to occur when the data FIFO becomes Half Full. This is the interrupt most
often used in background-task-based data acquisition.
EIFE set to 1 enables interrupts on FIFO Error. That is, anytime the FIFO is read from when it is already
empty, or when data is lost because the FIFO is full when an A/D conversion finishes.
CTR set to 1 causes start conversions to occur each time counter 2 (used in Mode 2) counts down to zero.
The other bits in this register must be cleared to zero for compatibility with future options.
Offset 4 Read Status, Clear Interrupt
This register is read to determine the status of various features on the card, primarily the state of the point-list
and data FIFOs, or to determine if a conversion has finished.
bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0
BUSY CFF CFH CF0 FF FH F0 EXT
The BUSY bit indicates the conversion is in process. A zero means the A/D is busy, a one means a
conversion is not in progress. This bit is one of the most important when not using interrupt modes. By
reading this bit you can determine when the A/D conversion has finished and know when to take the data.
CFF, CFH, CF0, FF, FH, and F0 indicate when LOW that the respective status is true. (C)FF is FIFO Full,
(C)FH is FIFO Half Full, and (C)F0 means FIFO Empty.
The EXT bit works like a digital input bit. It shows the current state of the External Start A/D pin on the
connector (pin 4). A/D conversions can be started by pulling this pin high if XSCE is set to one in Offset 4.
Offset 8, 9, A, and B 8254 Counter / Timer
Refer to the 8254 section for information on programming this device.
Offset C & D DAC 0
These registers are customarily written together in a single word write instruction. The value written is
immediately output on DAC 0.
Offset E & F DAC 1
These registers are customarily written together in a single word write instruction. The value written is
immediately output on DAC 1.

Manual PCI-A12-16A
19
Offset 10, 11, and 12 8255 Digital I/O Ports
These registers are the ports of the 8255; offset 10 is port A, offset 11 is port B, and offset 12 is port C. Each
port is 8 bits, for a total of 24 bits. Each port’s direction can configured independently via the control register
at offset 13. All ports power up as input ports. Each bit has a weak pull-up, so that with no signal applied, all
inputs read high.
Writing to an output port will update the data on that port. Reading from an output port will read back the
output data. Reading from an input port will read the current data on that port. Writing to an input port is
ignored.
Port C can be treated as two 4-bit ports, C Hi (bits 4-7) and C Lo (bits 0-3), instead of a single 8-bit port.
Often, one is configured as an input port and the other as an output port, to provide a few control signals in
each direction. Since writes to inputs are ignored, one can be written to without affecting the inputs of the
other.
Offset 13 8255 Control
This register is normally used to control the direction of the 8255 digital I/O ports. Port modes can also be set
here, however the card is only designed for mode 0; contact the factory for a custom solution if modes 1 or 2
are desired. Bit assignments in this control byte are as follows:
Bit Assignment Function
D0 Port C Lo (C0-C3) 1 = Input, 0 = Output
D1 Port B 1 = Input, 0 = Output
D2 Mode Selection (B & C Lo) Use 0
D3 Port C Hi (C4-C7) 1 = Input, 0 = Output
D4 Port A 1 = Input, 0 = Output
D5 Mode Selection (A & C Hi) Use 0
D6 Mode Selection (Mode 2) Use 0
D7 Mode Set Flag Use 1
Three common control bytes (in hex):
80 - Set all ports to output.
9B - Set all ports to input. This is their power-on configuration.
83 - Set ports A and C Hi to output, set ports B and C Lo to input.