Computerboards Cio-das801 User manual

CIO-DAS801 & 802

ComputerBoards, Inc.

Revision 2

October, 1999

means, electronic, mechanical, by photocopying, recording or otherwise without the prior written permission of ComputerBoards, Inc.

MEGA-FIFO, the CIO prefix to data acquisition board model numbers, the PCM prefix to data acquisition board model numbers,

PCM-DAS08, PCM-D24C3, PCM-DAC02, PCM-COM422, PCM-COM485, PCM-DMM, PCM-DAS16D/12, PCM-DAS16S/12,

PCM-DAS16D/16, PCM-DAS16S/16, Universal Library,Instacal, Harsh Environment Warranty and ComputerBoards are registered

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license is granted by implication or otherwise under any patent or copyrights of ComputerBoards, Inc.

Notice

ComputerBoards, Inc. does not authorize any ComputerBoards, Inc. product for use in life support systems

and/or devices without the written approval of the President of ComputerBoards, Inc. Life support

devices/systems are devices or systems which, a) are intended for surgical implantation into the body, or b)

support or sustain life and whose failure to perform can be reasonably expected to result in injury.

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HM CIO-DAS80#.lwp

TABLE OF CONTENTS

5: SPECIFICATIONS ...................................................................................... 18

4: COUNTER TIMER CIRCUIT ............................................................................ 143.1 REGISTER LAYOUT .................................................................................... 14

3: REGISTER ARCHITECTURE ............................................................................ 132.3.6 DIGITAL OUTPUTS & INPUTS ....................................................................... 122.3.2 ANALOG INPUTS ................................................................................. 122.3.1 CONNECTOR DIAGRAM ........................................................................... 122.3 SIGNAL CONNECTION ............................................................................... 112.2.7 Isolated Grounds / Differential Inputs ................................................................. 112.2.6 Isolated Grounds / Single-Ended Inputs ................................................................ 102.2.5 Common Mode Voltage Greater Than +/-10V ........................................................... 102.2.4 Common Mode Voltage < +/-10V / Differential Inputs .................................................... 92.2.3 Common Mode Voltage - Less Than +/-10V / Single-Ended Inputs ........................................... 92.2.2 Common Ground / Differential Inputs .................................................................. 82.2.1 Common Ground / Single-Ended Inputs ................................................................. 82.2 WIRING CONFIGURATIONS ............................................................................. 62.1.4 Determine Your System Type .......................................................................... 62.1.3 System Grounds and Isolation ......................................................................... 42.1.2 Differential Inputs .................................................................................. 42.1.1 Single-Ended Inputs ................................................................................. 42.1 ANALOG INPUTS ....................................................................................... 4

2: ANALOG CONNECTIONS ................................................................................ 31.3.5 INSTALLING THE CIO-DAS80# ....................................................................... 31.3.4 WAIT STATE ....................................................................................... 31.3.3 INTERRUPT LEVEL SELECT ......................................................................... 21.3.2 DIFFERENTIAL / SINGLE ENDED SELECT ............................................................ 11.3.1 BASE ADDRESS .................................................................................... 11.3 HARDWARE INSTALLATION ............................................................................ 11.2 SOFTWARE INSTALLATION ............................................................................. 11.1 INTRODUCTION ........................................................................................ 1

1: INSTALLATION ........................................................................................

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1: INSTALLATION

1.1 INTRODUCTION

This manual covers two boards, the CIO-DAS801 and the CIO-DAS802. These two boards are identical except for the programmable

input ranges available. The CIO-DAS802 offers more choices in the range from 10 volts to 0.625 volts, but the CIO-DAS801 offers a

wider range of choices from 10 volts down to 0.01 volts.

This manual will refer to both boards as CIO-DAS80# except in cases where these differences apply.

1.2 SOFTWARE INSTALLATION

Before you open your computer and install the board, install and run InstaCal, the installation, calibration and test utility included with

your board. InstaCal will guide you through switch and jumper settings for your board. Detailed information regarding these settings

can be found below. Refer to the Software Installation manual for InstaCal installation instructions.

1.3 HARDWARE INSTALLATION

There are two banks of switches and two jumpers to set on the CIO-DAS80# before installing your board into your computer.

1. BASE ADDRESS SWITCH. A base address must be chosen and selected via on-board switches.

2. INPUT SELECT SWITCHES. Analog inputs are differential or single-ended. You may choose either on a channel-by-channel

basis. The set of DIP switches on the board, labeled S2, 0 through 7, correspond to the channels 0 to 7 of the analog inputs.

3. INTERRUPT SELECT JUMPER. In order to take advantage of high speed transfers, you must provide the board with an inter-

rupt that is not used by other devices in your computer. Use the IR jumper to select an interrupt level between 2 and 7 or to dis-

able interrupts (X).

4. WAIT STATE JUMPER. A wait state jumper allows you to slow down a (future) computer bus that is too fast for the board.

(We have not seen the need for it yet.) Set jumper WSt to “ON” to enable wait states.

1.3.1 BASE ADDRESS

The base address of the CIO-DAS80# is set by switching a bank of DIP

switches on the board (Figure 2-1). This bank of switches is labeled ADDRESS

and numbered 9 to 3. Refer to the Software Installation Manual for instructions

for using InstaCal as an aid in setting the base address switches.

Ignore the word ON and the numbers printed on the switch.

The address is derived by the software adding up the weights of individual

switches to yield a base address. A 'weight' is active when the switch is down.

Shown to the right, switches 9 and 8 are down, all others are up. Weights 200H

and 100H are active, equaling 300H base address. Refer to Table 2-1 for PC I/O

addresses. Figure 1-1. Base Address Select

Switches

Table 1-1. I/O Addresses

SERIAL PORT3F8-3FFEGA2B0-2BF FLOPPY DISK3F0-3F7PARALLEL PRINTER270-27F SERIAL PORT3E8-3EFALT BUS MOUSE23C-23F CGA3D0-3DFBUS MOUSE238-23B EGA3C0-3CFEXPANSION UNIT (XT)210-21F PARALLEL PRINTER3BC-3BFGAME CONTROL200-20F MDA3B0-3BBHARD DISK (AT)1F0-1FF SDLC3A0-3AF80287 NUMERIC CO-P (AT)0F0-0FF SDLC380-38F8237 #2 (AT)0C0-0DF PARALLEL PRINTER378-37FNMI MASK (XT)0A0-0AF HARD DISK (XT)320-32F8259 PIC #2 (AT)0A0-0A1 PROTOTYPE CARD310-31FDMA PAGE REGISTERS080-08F PROTOTYPE CARD300-30F

CMOS RAM & NMI MASK (AT)

070-071 SERIAL PORT2F8-2FF8742 CONTROLLER (AT)060-064 SERIAL PORT2E8-2EF8255 PPI (XT)060-063 GPIB (AT)2E0-2E78253 TIMER040-043 EGA2D0-2DF8259 PIC #1020-021 EGA2C0-2CF8237 DMA #1000-00F

FUNCTIONHEX

RANGE

FUNCTIONHEX

RANGE

1.3.2 DIFFERENTIAL / SINGLE ENDED SELECT

The CIO-DAS80# has differential analog inputs. Differential inputs are 3-wire analog hookups consisting of a signal high, signal low

and chassis ground. The benefits of differential inputs are the ability to reject noise which affects both signal high and low, and the

ability to compensate for ground loops or potentials between signal low and chassis ground.

Although differential inputs are often preferable to single ended inputs, there are occasions when the floating nature of a differential

input can confound attempts to make a reading. In those cases, the CIO-DAS80# inputs can be converted to single-ended or modified

differential.

The CIO-EXP16 and CIO-EXP32 were designed to interface to a single-ended input. Failure to set the switches to single ended when

an EXP is connected will result in floating, unstable readings from the

EXP.

The analog inputs of the CIO-DAS80# may be set up as single ended or

differential. There are two ways to select between them.

The first method of selecting between the single ended and differential

inputs is with a set of eight switches located near the connector and

labeled 0-7 in white lettering on the board. In the down (off) position,

the input associated with that switch is in differential mode. In the up

(on) position the input is single-ended.

Figure 1-2 shows one analog input and the single-ended / differential

switch. Figure 1-2. Input Configuration Switch

The second method of converting the inputs to single-ended is to

install a SIP resistor pack at position RN2. This package of 10K resis-

tors provides a reference to ground for each of the eight Low Input

lines. This type of input behaves like a single-ended input since there

is a reference to ground and floating sources may be measured.

Figure 1-3 shows one analog input line with the SIP resistor installed.

Note that when the SIP resistor package is installed, all eight analog

inputs are single-ended.

If you intend to use an EXP board with the CIO-DAS80#, you should

not install the SIP resistor but you should set the Input Configuration

Switch to Single Ended for both the EXP channel and the CJC

channel.

1.3.3INTERRUPT LEVEL SELECT

The interrupt jumper need only be set if the software you are using requires it. The Uni-

versal Library and other programs which take advantage of the REP-INSW high speed

transfer capability of the board require an interrupt. If you do set the interrupt jumper,

please check your PC's current configuration for interrupt conflicts.

There is a jumper block on the CIO-DAS80# located just above the PC bus interface (gold

pins). The factory default setting has no interrupt level set (the jumper is in the 'X'

position). It is shown in Figure 1-4 set for IRQ 5.

Refer to Table 1-2 for typical IRQ assignments. Figure 1-4. IRQ Level Select Switches

Table 1-2. IRQ Assignments

Note: IRQ8-15 are AT onlyLPTIRQ7 UNASSIGNEDIRQ15FLOPPY DISKIRQ6

HARD DISKIRQ14HARD DISK (XT)

LPT (AT)

IRQ5 80287 NUMERIC CO-PIRQ13COM OR SDLCIRQ4 UNASSIGNEDIRQ12COM OR SDLCIRQ3

UNASSIGNEDIRQ11RESERVED (XT)

INT 8-15 (AT)

IRQ2 UNASSIGNEDIRQ10KEYBOARDIRQ1 RE-DIRECTED TO IRQ2 (AT)IRQ9TIMERIRQ0 REAL TIME CLOCK (AT)IRQ8PARITYNMI DESCRIPTIONNAMEDESCRIPTIONNAME

1.3.4 WAIT STATE

A wait state may be enabled on the CIO-DAS80# by selecting WAIT STATE ON at the jumper provided on the board. Enabling the

wait state causes the personal computer's bus transfer rate to slow down whenever the CIO-DAS80# is written to or read from. The

wait state jumper is provided in case you have a computer with an I/O bus transfer rate which is too fast for the CIO-DAS80#. If your

board were to fail sporadically in random ways, you could try using it with the wait state ON.

1.3.5 INSTALLING THE CIO-DAS80#

1. Turn the power off.

2. Remove the cover of your computer. Please be careful not to dislodge any of the cables installed on the boards in your computer

as you slide the cover off.

3. Locate an empty ISA expansion slot in your computer

4. Push the board firmly down into the expansion bus connector. If it is not seated fully it may fail to work and could short circuit

the PC bus power onto a PC bus signal. This could damage the motherboard in your PC as well as the CIO-DAS80#.

Figure 1-3.

Analog Input Configuration

2: ANALOG CONNECTIONS

2.1 ANALOG INPUTS

Before making actual connections, you may want to review the basic concepts of single-ended vs. differential inputs, and system

grounding and isolation.

2.1.1 Single-Ended Inputs

The input amplifier amplifies the voltage between the channel input line and LLGND. The single-ended input configuration actually

requires only one physical connection (wire) per channel and allows monitoring more channels than the (2-wire) differential configura-

tion using the same connector and on-board multiplexer.

However, since the input amplifier is amplifying the input voltage relative to its own low level ground, single-ended inputs are more

susceptible to both EMI (electromagnetic interference) and any ground noise at the signal source. Figures 2-1 and 2-2 show the single-

ended input configuration.

Figure 2-1. Single-Ended Input

Figure 2-2. Common-Mode voltage on Single-Ended Input

2.1.2 Differential Inputs

Differential amplifiers amplify the voltage between two distinct input signals. Within a certain range (referred to as the common mode

range), the amplified value is almost independent of signal source to board ground variations. A differential input is also much more

immune to EMI than a single-ended one. Most EMI noise induced in one lead is also induced in the other. Since the amplifier only

amplifies the difference between the two leads, and the EMI common to both inputs is ignored. This effect is a major reason for using

twisted-pair wire as the twisting assures that both wires are subject to virtually identical external influences. Figure 2-3 below shows

the basic differential input configuration.

Input

Amp To A/D

I/O

Connector

LL GND

CH IN

Note: Input MUX omitted for

clarity.

Input

Amp To A/D

LL GND

CH IN

Vs Vs + Vg2 - Vg1

Any voltage differential between grounds

g1 and g2 shows up as an error signal

at the input amplifier

Sin

le-ended input with Common Mode Volta

Figure 2-3. Differential Input

Before describing grounding and isolation, it is important to understand the concepts of common mode, and common mode range (CM

Range). Common mode voltage is labeled in Figure 2-4 as Vcm. Though differential inputs measure the voltage between two signals,

without (almost) respect to either signal’s voltages relative to ground, there is a limit to how far away from ground either signal can go.

Although the board has differential inputs, it will not measure the difference between 100V and 101V as 1 Volt (because 100V would

destroy the board!). This limitation or common mode range is depicted graphically in Figure 2-5. The common mode range is +/- 10

Volts. Even in differential mode, no input signal can be measured if it is more than +/-10V from the board’s low level ground

(LLGND).

Figure 2-4. Common-Mode Voltage at a Differential Input

Input

Amp To A/D

Differential Input

I/O

Connector

LL GND

CH High

CH Low

Input

Amp To A/D

Differential

Input

LL GND

CH High

CH Low

Vs Vs

Vcm

Common Mode Volta

e (Vcm) is i

nored

differential input confi

uration. However,

note that Vcm + Vs must remain within

the amplifier’s common mode ran

e of ±10V

Vcm = V

2 - V

Figure 2-5. Common Mode Voltage Allowable Range

2.1.3 System Grounds and Isolation

There are three scenarios possible when connecting your signal source to the board:

1. The board and the signal source may have the same (or common) ground. This signal source may be connected directly to

the board.

2. The board and the signal source may have an offset voltage between their grounds (AC and/or DC). This offset is com-

monly referred to as a common mode voltage. Depending on the magnitude of this voltage, it may or may not be possible to

connect the board directly to your signal source. We will discuss this topic further in a later section.

3. The board and the signal source may already have isolated grounds. This signal source may be connected directly to the

board.

2.1.4 Determine Your System Type

Perform the following test: using a battery-powered voltmeter, measure the voltage between ground at your signal source and ground at

your PC. Place one voltmeter probe on the PC ground and the other on the signal source ground. Measure both the AC and DC Volt-

ages.

If you do not have access to a voltmeter, skip the test and read the following three sections. You may be able to identify your system

type from the descriptions provided.

If both AC and DC readings are 0.00 volts, you may have a system with common grounds. However, since voltmeters will average out

high frequency signals, there is no guarantee. Please refer to the section below titled Common Grounds.

If you measure reasonably stable AC and DC voltages, your system has an offset voltage between the grounds category. This offset is

referred to as a Common Mode Voltage. Please be careful to read the following warning and then proceed to the section describing

Common Mode systems.

+1V

-13V

+2V

-12V

+3V

-11V

+4V

-10V

+5V

-9V

+6V

-8V

+7V

-7V

+8V

-6V

+9V

-5V

+10V

-4V

+11V

-3V

+12V

-2V

+13V

-1V

Gray area represents common mode ran

Both V+ and V- must always remain within

the common mode ran

e relative to LL Gnd

Vcm (Common Mode Volta

e) = +5 Volts

Vcm

With Vcm= +5VDC,

+Vs must be less than +5V, or the common mode ran

e will be exceeded (>+10V)

WARNING

If either the AC or DC voltage is greater than 10 volts, do not connect the board to this signal source. You are beyond the board’s

usable common-mode range. You must either adjust your grounding system or add special isolation signal conditioning to take useful

measurements. A ground offset voltage of more than 30 volts will likely damage the board and possibly your computer. Note that an

offset voltage much greater than 30 volts will not only damage your electronics, but it may be hazardous to your health.

If you cannot obtain a reasonably stable DC voltage measurement between the grounds, or the voltage drifts around considerably, the

two grounds are most likely isolated. The easiest way to check for isolation is to change your voltmeter to it’s ohm scale and measure

the resistance between the two grounds. It is recommended that you turn both systems off prior to taking this resistance measurement.

If the measured resistance is more than 100 Kohm, it’s a fairly safe bet that your system has electrically isolated grounds.

a. Systems with Common Grounds

In the simplest (but perhaps least likely) case, your signal source will have the same ground as the board. This would typically occur

when providing power or excitation to your signal source directly from the board. There may be other common ground configurations,

but it is important to note that any voltage between the board’s ground and your signal ground is a potential error voltage if you set up

your system based on a common ground assumption.

As a safe rule of thumb, if your signal source or sensor is not connected directly to an LLGND pin on your board, it’s best to assume

that you do not have a common ground even if your voltmeter measured 0.0 Volts. Configure your system as if there is ground offset

voltage between the source and the board. This is especially true if you are using high gains, since ground potentials in the sub-

millivolt range will be large enough to cause A/D errors, yet will not likely be measured by your handhold voltmeter.

b. Systems with Common Mode (ground offset) Voltages

The most frequently encountered grounding scenario involves grounds that are somehow connected, but have AC and/or DC offset

voltages between the board and signal source grounds. This offset voltage my be AC, DC or both and may be caused by a wide array

of phenomena including EMI pickup, resistive voltage drops in ground wiring and connections, etc. Ground offset voltage is a more

appropriate term to describe this type of system, but since our goal is to keep things simple, and help you make appropriate connec-

tions, we’ll stick with our somewhat loose usage of the phrase Common Mode.

c. Small Common Mode Voltages

If the voltage between the signal source ground and board’s ground is small, the combination of the ground voltage and input signal

will not exceed the board’s +/-10V common mode range, (i.e. the voltage between grounds, added to the maximum input voltage, must

stay within +/-10V). This input is compatible with the board and the system may be connected without additional signal conditioning.

Fortunately, most systems will fall in this category and have a small voltage differential between grounds.

d. Large Common Mode Voltages

If the ground differential is large enough, the board’s +/- 10V common mode range will be exceeded (i.e. the voltage between the

board and signal source grounds, added to the maximum input voltage you’re trying to measure exceeds +/-10V). In this case the board

cannot be directly connected to the signal source. You will need to change your system grounding configuration or add isolation signal

conditioning. (Please look at our ISO-RACK and ISO-5B-series products to add electrical isolation, or give our technical support

group a call to discuss other options.)

NOTE

Do not rely on the earth prong of a 120VAC receptacle for signal ground connections. Different ground plugs may have large and

potentially even dangerous voltage differentials. Remember that the ground pins on 120VAC outlets on different sides of the room may

only be connected in the basement. This leaves the possibility that the “ground” pins may have a significant voltage differential (espe-

cially if the two 120VAC outlets happen to be on different phases!)

e. The board and signal source already have isolated grounds

Some signal sources will already be electrically isolated from the board. The diagram below shows a typical isolated ground system.

These signal sources are often battery powered, or are fairly expensive pieces of equipment (isolation can be expensive). Isolated

ground systems provide excellent performance but require extra effort during connections to assure optimum performance is obtained.

Please refer to the following sections for further details.

2.2 WIRING CONFIGURATIONS

Combining all the grounding and input type possibilities provides us with the following potential connection configurations. The com-

binations along with our recommendations on usage are shown in Table 2-1.

Table 2-1. Input Type and Grounding Recommendations

RecommendedDifferential Inputs

Already Isolated

Grounds

AcceptableSingle-ended InputsAlready Isolated Grounds

Unacceptable without

adding Isolation

Differential Inputs

Common Mode

Voltage > +/-10V

Unacceptable without

adding Isolation

Single-Ended Inputs

Common Mode

Voltage > +/- 10V

RecommendedDifferential Inputs

Common Mode

Voltage < +/-10V

Not RecommendedSingle-Ended Inputs

Common Mode

Voltage < +/-10V

AcceptableDifferential InputsCommon Ground

RecommendedSingle-Ended InputsCommon Ground

RecommendationInput ConfigurationGround Category

The following sections have recommended input wiring schemes for input configuration/grounding combinations.

2.2.1 Common Ground / Single-Ended Inputs

Single-ended is the recommended configuration for common ground connections. However, if some of your inputs are common ground

and some are not, we recommend you use the differential mode. There is no performance penalty (other than loss of channels) for

using a differential input to measure a common ground signal source. However the reverse is not true. Figure 2-6 below shows a rec-

ommended connection diagram for a common ground / single-ended input system

Figure 2-6. Single-Ended Input with Common Ground Connection

Input

Amp To A/D

A/D Board

I/O

Connector

LL GND

CH IN





Signal

Source with

Common Gnd

Optional wire

since signal source

and A/D board share

common ground

Signal source and A/D board

sharing common ground connected

to single-ended input.

2.2.2 Common Ground / Differential Inputs

The use of differential inputs to monitor a signal source with a common ground is a acceptable configuration though it requires more

wiring and offers fewer channels than selecting a single-ended configuration. Figure 2-7 below shows the recommended connections in

this configuration.

Figure 2-7. Differential Input with Common Ground

2.2.3 Common Mode Voltage - Less Than +/-10V / Single-Ended Inputs

This configuration is not recommended. Here, the term common-mode has no meaning in a single-ended system and this case would be

better described as a system with offset grounds. In any case, try this configuration. No system damage should occur and depending on

the overall accuracy you require, you may receive acceptable results.

Input

Amp To A/D

A/D Board

I/O

Connector

LL GND

CH High

CH Low





Signal

Source with

Common Gnd

Optional wire

since signal source

and A/D board share

common ground

Required connection

of LL GND to CH Low

Signal source and A/D board

sharing common ground connected

to differential input.

2.2.4 Common Mode Voltage < +/-10V / Differential Inputs

Always monitor systems with varying ground potentials used with differential mode. Care is required to verify that the sum of the input

signal and the ground differential (referred to as the common-mode voltage) does not exceed the common-mode range of the A/D

board (+/-10V on the board). Figure 2-8 shows recommended connections in this configuration.

Figure 2-8. Common Mode Voltage < +/-10V / Differential Inputs

2.2.5 Common Mode Voltage Greater Than +/-10V

The board will not directly monitor signals with common mode voltages greater than +/-10V. You will either need to alter the system

ground configuration to reduce the overall common mode voltage, or add isolated signal conditioning between the source and your

board. See Figure 2-9 and 2-10 below.

Figure 2-9. High Common-Mode Voltage and Isolation Barrier Requirement

Figure 2-10. High Common-Mode Voltage & Isolation Barrier w/Pull-Down Resistor

Input

Amp To A/D

A/D Board

I/O

Connector

LL GND

CH Hi

CH Low





Signal Source

with Common

Mode Voltage

nal source and A/D board

with common mode volta

connected to a differential input.

GND

The voltage differential

between these grounds,

added to the maximum

input signal must stay

within +/-10V

System with a Large Common Mode Voltage,

Connected to a Single-Ended Input

I/O

Connector

Input

Amp To A/D

LL GND

CH IN

A/D Board





arge common

mode voltage

between signal

source & A/D board

GND

Barrier

When the volta

e difference

between si

nal source and

A/D board

round is lar

enou

h so the A/D board’s

common mode ran

e is

exceeded, isolated si

nal

conditionin

must be added.

System with a Large Common Mode Voltage,

Connected to a Differential Input





arge common

mode voltage

between signal

source & A/D board

GND

Isolation

Barrier

When the voltage difference

between signal source and

A/D board ground is large

enough so the A/D board’s

common mode range is

exceeded, isolated signal

conditioning must be added.

Input

Amp To A/D

A/D Board

I/O

Connector

LL GND

CH High

CH Low

10 K

10K is a recommended value. You may short LL GND to CH Low

instead, but this will reduce your system’s noise immunity.

2.2.6 Isolated Grounds / Single-Ended Inputs

Single-ended inputs can be used to monitor isolated inputs, though the use of the differential mode will increase your system’s noise

immunity. Figure 2-11 shows the recommended connections is this configuration.

Figure 2-11. Isolated Signal Source to Single-Ended Input

2.2.7 Isolated Grounds / Differential Inputs

Optimum performance with isolated signal sources is assured with the use of differential inputs. Figure 2-11 shows the recommended

connections for this configuration.

Figure 2-11. Isolated Signal Source Connected to a Differential Input

Isolated Si

nal Source

Connected to a Sin

le-Ended Input

I/O

Connector

Input

Amp To A/D

LL GND

CH IN

A/D Board





Isolated

signal

source

Input

Amp To A/D

A/D Board

I/O

Connector

LL GND

CH High

CH Low





Signal Source

and A/D Board

Already Isolated.

Already isolated signal source

and A/D board connected to

a differential input.

GND

These

rounds are

electrically isolated.

10 K

10K is a recommended value. You ma

short LL GND to CH Low

instead, but this will reduce

our s

stem’s noise immunit

2.3 SIGNAL CONNECTION

Signal connection is important in applying a data acquisition board. In addition to wrong connections, which is the most common

cause of customer calls to tech support, is the possibility of ground loops, floating signal sources and excessive common mode voltage.

Connecting signals to a data acquisition board is not difficult. Please follow the examples shown here and pay close attention to the

grounding shared between the PC and the signal source.

2.3.1 Connector Diagram

The CIO-DAS80# analog connector is a 37 pin D type connector accessible

from the rear of the PC through the expansion backplate (Figure 2-12). The

connector accepts female 37 D type connectors, such as those on the

C73FF-2, 2 foot cable with connectors. The connector pin names Ch# Low

and Ch# High are the differential inputs of the CIO-DAS80#.

If frequent changes to signal connections or signal conditioning are

required, refer to the information on the CIO-TERMINAL and CIO-

MINI37 screw terminal boards. If additional channels or signal condition-

ing is required, refer to the information on the CIO-EXP32, 32 channel

analog multiplexer/amplifier. Isolation amplifiers may be mounted using

the ISO-RACK08 and 5B isolation modules.

2.3.2 Analog Inputs

Analog inputs on the CIO-DAS80# are designed to accept voltage signals

for measurement.

The analog inputs may be configured in three different ways:

1. True differential inputs. For sources with a separate ground, com-

mon to the PC.

2. Pseudo-differential inputs used for floating sources has noise rejec-

tion capability

3. Single ended inputs. Also used for floating sources.

The manner of configuring the analog inputs and the schematic of those

configurations is explained earlier in the manual. This section covers the

implications of a given connection and shows how to make that connection

Figure 2-12. Analog Connector

WARNING - PLEASE READ

TIP: Using a voltmeter, measure the AC and DC voltage between the ground signal at the signal source and the PC.

Place the red probe on the PC ground and the black probe on the signal ground. If there is a difference of more than

10 volts, do not connect the CIO-DAS80# to this signal source because you will not be able to make any reading. If

the difference is more than 30 volts, DO NOT connect this signal to the board because it will damage the board and

possibly the computer. WARNING: Use great care when measuring any voltage. Voltages over 30V can be dan-

gerous to your health.

2.3.3 Single-Ended Inputs

A single ended input is two wires connected to the CIO-DAS80#; a channel high (CH# HI) and a Low Level Ground (LLGND). The

LLGND signal must be the same ground the PC is on. The CH# HI is the signal voltage. Single-ended mode is selected via a switch.

2.3.4 Floating Differential

A floating differential input is two wires from the signal source and a 10K ground reference resistor installed at the CIO-DAS80#

input. The two signals from the signal source are Signal High (CH# High) and Signal Low (CH# Low). The reference resistor is con-

nected between the CIO-DAS80# CH# Low and LLGND pins. This is accomplished with the installation of the SIP resistor pack.

A floating differential hookup is handy when the signal source is floating with respect to ground, such as a battery, 4-20mA transmitter

or if the lead lengths are long or subject to EMI interference. The floating differential input will reject up to 10V of EMI on the signal

wires.

WARNING! Verify that the signal source really floating. Check it with a ohmmeter before risking the CIO-DAS80# and PC.

2.3.5 Fully Differential

A differential signal has three wires from the signal source. The signals are Signal High (CH# High), Signal Low (CH# Low) andSig-

nal Ground (LLGND).

A differential connection allows you to connect the CIO-DAS80# to a signal source with a ground that is different than the PC ground,

but less than 10V difference, and still make a true measurement of the signal between CH# High and CH# Low.

EXAMPLE: A laboratory instrument with its own wall plug. There are sometimes voltage differences in wall GND between outlets.

2.3.6 Digital Inputs and Outputs

All the digital inputs and outputs on the CIO-DAS80# are TTL level. TTL is an electronics industry term, short for Transistor Transis-

tor Logic, with describes a standard for digital signals which are either at TTL low or TTL high; levels which are detected by all other

TTL devices. For a listing of the TTL level specifications for these digital lines, please see the specifications at the end of this manual.

There are three digital inputs and four digital outputs. The digital inputs are buffered by a register on the board. Each time the register

is read, the current high/low state of the digital I/O lines is obtained. The digital outputs are controlled by a register on the board and

are updated each time the register is written to. The lines are pulled high so a logical-one is read if no signal is connected to an input.

The digital lines also are used to control external EXP boards (all four outputs) and to trigger and gate A/D conversions (Digital In 1).

3: REGISTER ARCHITECTURE

All of the programmable functions of the CIO-DAS801 and 802 are accessible through the control and data registers.

3.1 REGISTER LAYOUT

The CIO-DAS801 / 802 is controlled and monitored by writing to and reading from 16 consecutive 8-bit I/O addresses. The first

address, or BASE ADDRESS, is determined by setting a bank of switches on the board.

Register manipulation is best left to experienced programmers as most of the possible functions are implemented in easy-to-use Uni-

versal Library routines.

To write to or read from a register in decimal or hexadecimal, the following weights apply:

801287406462032510164883 442 221 110 HEX VALUEDECIMAL VALUEBIT POSITION

Each register has eight bits which may be a byte of data or eight individual bit read/write functions. To write control words or data to a

register, the individual bits must be set to 0 or 1 then combined to form a byte. Data read from registers is analyzed to determine

which bits are on or off.

The method of programming required to set/read bits from bytes is beyond the scope of this manual. Summaries of the registers and

their read and write functions are given on Tables 3-1 through 3-6.

Table 3-1. Register Write Functions

8254 Counter/Timer Control Register

Base + 7

Cascade Pre-scaler

8254 C/T 2 Control Register

Base + 6

A/D Timer

8254 C/T 1 Control Register

Base + 5

8254 C/T 0 Control Register

Base + 4

Range/Control Select

R0R1R2R3ENHFCS0CS1CSEBase + 3

Scan Limits Register

SC0SC1SC2EC0EC1EC2NANACS1/0=1/0

Conversion Control

ITECASCDTENIEOCEACSGTENNAHCENCS1/0=0/1

Control Register 1

MA0MA1MA2INTEOP1OP2OP3OP4CS1/0=0/0

Special Function - (Depends on value of CS0,1)

Base + 2

Start Conversion

Base + 1

Start Conversion

Base + 0

D0D1D2D3D4D5D6D7

Write

Functions Data Bits Function

Table 3-2. Control Register Select Coding

ID RegisterNot defined1

1Status Register #2Scan Limits Reg01 Status Register #2Conversion Control Register10 Status Register #2

Control Reg # 1

00 Read Function

Write Function

CS0CS1 Control Register Selected

Table 3-3. Range (Gain) Select Codes

Uni: 0 to 0.01V (g=1000)Uni: 0 to 1.25V (g=8)1111 Bip: +/- 0.005V(g=1000)Bip: +/- 625mV (g=8)0111 Uni: 0 to 0.1V (g=100)Uni: 0 to 2.5V (g=4)1011 Bip: +/- 0.05V (g=100)Bip: +/- 1.25V (g=4)0011 Uni: 0 to 1V (g=10)Uni: 0 to 5V (g=2)1101 Bip: +/- 0.5V (g=10)Bip: +/- 2.5V (g=2)0101 Uni: 0 to 10V (g=1)Uni: 0 to 10V (g=1)1001 Bip: +/- 10V (g=0.5)Bip: +/- 10V (g=0.5)0001 Bip: +/- 5V (g=1)Bip: +/- 5V (g=1)0000 DAS-801DAS-802R0R1R2R3 Range / (Gain)Range (Gain) Select: