Tektronix M1000, M2000 Users Guide

M1000/M2000

User Guide

A GREATER MEASURE OF CONFIDENCE

WARRANTY

Hardware

Keithley Instruments, Inc. warrants that, for a period of one (1) year from the date of shipment (3 years for Models 2000, 2001, 2002, 2010 and 2700), the
Keithley Hardware product will be free from defects in materials or workmanship. This warranty will be honored provided the defect has not been caused
by use of the Keithley Hardware not in accordance with the instructions for the product. This warranty shall be null and void upon: (1) any modification of
Keithley Hardware that is made by other than Keithley and not approved in writing by Keithley or (2) operation of the Keithley Hardware outside of the
environmental specifications therefore.

Upon receiving notification of a defect in the Keithley Hardware during the warranty period, Keithley will, at its option, either repair or replace such Keithley Hard­ware. During the first ninety days of the warranty period, Keithley will, at its option, supply the necessary on site labor to return the product to the condition prior to
the notification of a defect. Failure to notify Keithley of a defect during the warranty shall relieve Keithley of its obligations and liabilities under this warranty.

Other Hardware

The portion of the product that is not manufactured by Keithley (Other Hardware) shall not be covered by this warranty, and Keithley shall have no duty of
obligation to enforce any manufacturers' warranties on behalf of the customer. On those other manufacturers’ products that Keithley purchases for resale,
Keithley shall have no duty of obligation to enforce any manufacturers’ warranties on behalf of the customer.

Software

Keithley warrants that for a period of one (1) year from date of shipment, the Keithley produced portion of the software or firmware (Keithley Software) will
conform in all material respects with the published specifications provided such Keithley Software is used on the product for which it is intended and other­wise in accordance with the instructions therefore. Keithley does not warrant that operation of the Keithley Software will be uninterrupted or error-free and/
or that the Keithley Software will be adequate for the customer's intended application and/or use. This warranty shall be null and void upon any modification
of the Keithley Software that is made by other than Keithley and not approved in writing by Keithley.

If Keithley receives notification of a Keithley Software nonconformity that is covered by this warranty during the warranty period, Keithley will review the
conditions described in such notice. Such notice must state the published specification(s) to which the Keithley Software fails to conform and the manner
in which the Keithley Software fails to conform to such published specification(s) with sufficient specificity to permit Keithley to correct such nonconfor­mity. If Keithley determines that the Keithley Software does not conform with the published specifications, Keithley will, at its option, provide either the
programming services necessary to correct such nonconformity or develop a program change to bypass such nonconformity in the Keithley Software.
Failure to notify Keithley of a nonconformity during the warranty shall relieve Keithley of its obligations and liabilities under this warranty.

Other Software

OEM software that is not produced by Keithley (Other Software) shall not be covered by this warranty, and Keithley shall have no duty or obligation to
enforce any OEM's warranties on behalf of the customer.

Other Items

Keithley warrants the following items for 90 days from the date of shipment: probes, cables, rechargeable batteries, diskettes, and documentation.

Items not Covered under Warranty

This warranty does not apply to fuses, non-rechargeable batteries, damage from battery leakage, or problems arising from normal wear or failure to follow
instructions.

Limitation of Warranty

This warranty does not apply to defects resulting from product modification made by Purchaser without Keithley's express written consent, or by misuse
of any product or part.

Disclaimer of Warranties

EXCEPT FOR THE EXPRESS WARRANTIES ABOVE KEITHLEY DISCLAIMS ALL OTHER WARRANTIES, EXPRESS OR IMPLIED, INCLUD­ING WITHOUT LIMITATION, ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. KEI­THLEY DISCLAIMS ALL WARRANTIES WITH RESPECT TO THE OTHER HARDWARE AND OTHER SOFTWARE.

Limitation of Liability

KEITHLEY INSTRUMENTS SHALL IN NO EVENT, REGARDLESS OF CAUSE, ASSUME RESPONSIBILITY FOR OR BE LIABLE FOR: (1)
ECONOMICAL, INCIDENTAL, CONSEQUENTIAL, INDIRECT, SPECIAL, PUNITIVE OR EXEMPLARY DAMAGES, WHETHER CLAIMED
UNDER CONTRACT, TORT OR ANY OTHER LEGAL THEORY, (2) LOSS OF OR DAMAGE TO THE CUSTOMER'S DATA OR PROGRAM­MING, OR (3) PENALTIES OR PENALTY CLAUSES OF ANY DESCRIPTION OR INDEMNIFICATION OF THE CUSTOMER OR OTHERS FOR
COSTS, DAMAGES, OR EXPENSES RELATED TO THE GOODS OR SERVICES PROVIDED UNDER THIS WARRANTY.

Keithley Instruments, Inc. 28775 Aurora Road • Cleveland, Ohio 44139 • 440-248-0400 • Fax: [phone]

1-888-KEITHLEY (534-8453) • www.keithley.com

Sales Offices:BELGIUM: Bergensesteenweg 709 • B-1600 Sint-Pieters-Leeuw • 02-363 00 40 • Fax: [phone]

CHINA: Yuan Chen Xin Building, Room 705 • 12 Yumin Road, Dewai, Madian • Beijing 100029 • 8610-6202-2886 • Fax: [phone]
FINLAND: Tietäjäntie 2 • 02130 Espoo • Phone: [phone] • Fax: [phone]
FRANCE: 3, allée des Garays • 91127 Palaiseau Cédex • 01-64 53 20 20 • Fax: [phone]
GERMANY: Landsberger Strasse 65 • 82110 Germering • 089/84 93 07-40 • Fax: [phone]
GREAT BRITAIN: Unit 2 Commerce Park, Brunel Road • Theale • Berkshire RG7 4AB • 0118 929 7500 • Fax: [phone]
INDIA: Flat 2B, Willocrissa • 14, Rest House Crescent • Bangalore 560 001 • 91-80-509-1320/21 • Fax: [phone]
ITALY: Viale San Gimignano, 38 • 20146 Milano • 02-48 39 16 01 • Fax: [phone]
JAPAN: New Pier Takeshiba North Tower 13F • 11-1, Kaigan 1-chome • Minato-ku, Tokyo 105-0022 • 81-3-5733-7555 • Fax: [phone]
KOREA: 2FL., URI Building • 2-14 Yangjae-Dong • Seocho-Gu, Seoul 137-888 • 82-2-574-7778 • Fax: [phone]
NETHERLANDS: Postbus 559 • 4200 AN Gorinchem • 0183-635333 • Fax: [phone]
SWEDEN: c/o Regus Business Centre • Frosundaviks Allé 15, 4tr • 169 70 Solna • 08-509 04 679 • Fax: [phone]
SWITZERLAND: Kriesbachstrasse 4 • 8600 Dübendorf • 01-821 94 44 • Fax: [phone]
TAIWAN: 1FL., 85 Po Ai Street • Hsinchu, Taiwan, R.O.C. • 886-3-572-9077• Fax: [phone]

4/02

The

MI

000/M2000

User

Guide

Revision

Copyright

Par1

Number:

A,

-

Keiihley

May

24744

1988

MetraByte

Corp.

1988

Warranty Information

All products manufactured by Keithley MetraByte are warranted against defective materials

and

worksmanship for a period
purchaser. Any product
option
products damaged by improper use.

of

Keithley MetraI3yte.

that

of

one

year from the date

is

found to be defective within

be

repaired

or

replaced.

of

deLivery

the

This

warran@ does

to

the

original

wamty period will, at the

not

apply

Warning

to

Keithleg MetraByte

consequent

designed

to

with

for use

in

the use

components of a level

life

assumes

of

this

support

no

liability

product.

of

or

critical applications.

for

This

reliability suitable

damages

product

is

Disclaimer

Information furnished by Keithley MetraByte
However. the Keithley MetraByte corporation assumes no responsibility for the
information nor
result
rights

from

of

Keithley MetraByte Corporation.

its

for

use.

any

infringements

No

license

is

granted

of

is

believed

patents or other rights

by

implication

to

be

or

otherwise

accurate

of

and

third parties that

under

Notes

Keithley MetraByte/Asyst/DAC
Basicm

IBM@

is

a

trademark

is

a

registered trademark

of

Dartmouth College.

is

also referred

of

International Business Machines Corporation.

to

here-in

as

Kei.Mey

not

reliable.

use

any

patent

MetraByte.

of

may

such

PC,

XT,

AT.

PS/2,

International Business Machines Corporation.

Microsoft@

Turbo

is

C@

is a registered trademark

and

Micro Channel Architecture@

a registered trademark

of

Microsoft corporation.

of

Borland International,

-iv

-

(MCA)

are trademarks

of

New Contact Information

Keithley Instruments, Inc.

28775 Aurora Road

Cleveland, OH 44139

Technical Support: 1-888-KEITHLEY

Monday – Friday 8:00 a.m. to 5:00 p.m (EST)

Fax: [phone]

Visit our website at http://www.keithley.com

Safety Precautions

The following safety precautions should be observed before using
this product and any associated instrumentation. Although some in­struments and accessories would normally be used with non-haz­ardous voltages, there are situations where hazardous conditions
may be present.

This product is intended for use by qualified personnel who recog­nize shock hazards and are familiar with the safety precautions re­quired to avoid possible injury. Read and follow all installation,
operation, and maintenance information carefully before using the
product. Refer to the manual for complete product specifications.

If the product is used in a manner not specified, the protection pro­vided by the product may be impaired.

The types of product users are:

Responsible body is the individual or group responsible for the use

and maintenance of equipment, for ensuring that the equipment is
operated within its specifications and operating limits, and for en­suring that operators are adequately trained.

Operators use the product for its intended function. They must be

trained in electrical safety procedures and proper use of the instru­ment. They must be protected from electric shock and contact with
hazardous live circuits.

Maintenance personnel perform routine procedures on the product

to keep it operating properly, for example, setting the line voltage
or replacing consumable materials. Maintenance procedures are de­scribed in the manual. The procedures explicitly state if the operator
may perform them. Otherwise, they should be performed only by
service personnel.

Service personnel are trained to work on live circuits, and perform

safe installations and repairs of products. Only properly trained ser­vice personnel may perform installation and service procedures.

Keithley products are designed for use with electrical signals that
are rated Installation Category I and Installation Category II, as de­scribed in the International Electrotechnical Commission (IEC)
Standard IEC 60664. Most measurement, control, and data I/O sig­nals are Installation Category I and must not be directly connected
to mains voltage or to voltage sources with high transient over-volt­ages. Installation Category II connections require protection for
high transient over-voltages often associated with local AC mains
connections. Assume all measurement, control, and data I/O con­nections are for connection to Category I sources unless otherwise
marked or described in the Manual.

Exercise extreme caution when a shock hazard is present. Lethal
voltage may be present on cable connector jacks or test fixtures. The
American National Standards Institute (ANSI) states that a shock
hazard exists when voltage levels greater than 30V RMS, 42.4V
peak, or 60VDC are present. A good safety practice is to expect

that hazardous voltage is present in any unknown circuit before
measuring.

Operators of this product must be protected from electric shock at
all times. The responsible body must ensure that operators are pre­vented access and/or insulated from every connection point. In
some cases, connections must be exposed to potential human con­tact. Product operators in these circumstances must be trained to
protect themselves from the risk of electric shock. If the circuit is
capable of operating at or above 1000 volts, no conductive part of

the circuit may be exposed.

Do not connect switching cards directly to unlimited power circuits.
They are intended to be used with impedance limited sources.
NEVER connect switching cards directly to AC mains. When con­necting sources to switching cards, install protective devices to lim­it fault current and voltage to the card.

Before operating an instrument, make sure the line cord is connect­ed to a properly grounded power receptacle. Inspect the connecting
cables, test leads, and jumpers for possible wear, cracks, or breaks
before each use.

When installing equipment where access to the main power cord is
restricted, such as rack mounting, a separate main input power dis­connect device must be provided, in close proximity to the equip­ment and within easy reach of the operator.

For maximum safety, do not touch the product, test cables, or any
other instruments while power is applied to the circuit under test.
ALWAYS remove power from the entire test system and discharge
any capacitors before: connecting or disconnecting cables or jump­ers, installing or removing switching cards, or making internal
changes, such as installing or removing jumpers.

Do not touch any object that could provide a current path to the com­mon side of the circuit under test or power line (earth) ground. Always
make measurements with dry hands while standing on a dry, insulated
surface capable of withstanding the voltage being measured.

The instrument and accessories must be used in accordance with its
specifications and operating instructions or the safety of the equip­ment may be impaired.

Do not exceed the maximum signal levels of the instruments and ac­cessories, as defined in the specifications and operating informa­tion, and as shown on the instrument or test fixture panels, or
switching card.

When fuses are used in a product, replace with same type and rating
for continued protection against fire hazard.

Chassis connections must only be used as shield connections for
measuring circuits, NOT as safety earth ground connections.

If you are using a test fixture, keep the lid closed while power is ap­plied to the device under test. Safe operation requires the use of a
lid interlock.

5/02

If or is present, connect it to safety earth ground using the
wire recommended in the user documentation.

!

The symbol on an instrument indicates that the user should re­fer to the operating instructions located in the manual.

The symbol on an instrument shows that it can source or mea­sure 1000 volts or more, including the combined effect of normal
and common mode voltages. Use standard safety precautions to
avoid personal contact with these voltages.

The WARNING heading in a manual explains dangers that might
result in personal injury or death. Always read the associated infor­mation very carefully before performing the indicated procedure.

The CAUTION heading in a manual explains hazards that could
damage the instrument. Such damage may invalidate the warranty.

Instrumentation and accessories shall not be connected to humans.
Before performing any maintenance, disconnect the line cord and

all test cables.

To maintain protection from electric shock and fire, replacement
components in mains circuits, including the power transformer, test
leads, and input jacks, must be purchased from Keithley Instru­ments. Standard fuses, with applicable national safety approvals,
may be used if the rating and type are the same. Other components
that are not safety related may be purchased from other suppliers as
long as they are equivalent to the original component. (Note that se­lected parts should be purchased only through Keithley Instruments
to maintain accuracy and functionality of the product.) If you are
unsure about the applicability of a replacement component, call a
Keithley Instruments office for information.

To clean an instrument, use a damp cloth or mild, water based
cleaner. Clean the exterior of the instrument only. Do not apply
cleaner directly to the instrument or allow liquids to enter or spill
on the instrument. Products that consist of a circuit board with no
case or chassis (e.g., data acquisition board for installation into a
computer) should never require cleaning if handled according to in­structions. If the board becomes contaminated and operation is af­fected, the board should be returned to the factory for proper
cleaning/servicing.

MIOQO

SERIES

USERS

R

EMS

The information in this publication has been carefully checked and is believed

to be accurate; however, no responsibility is assumed for possible inaccuracies

or omissions. Applications information in this manual is intended

suggestions for possible use

a

specific application. Specifications may be subject

Ml000

explosive environment unless enclosed in approved explosion-proof housings

MANUAL

I0

N

:

3/30/87

modules are

of

the products and not as explicit performance in

to

not

intrinsically safe devices and should

change

without

not

notice.

be used in an

as

TABLE OF CONTENTS

Warranty

5

CHAPTER1 Getting Started

Default Mode

1-1

Quick Hook-Up 1-2

CHAPTER 2 Functional Description

Block Diagram 2-4

CHAPTER 3 Communications

RS-232C

3-2

Single Module and Multi-party Connection
Software Considerations
Changing Baud Rate 3-5
Using a Daisy-Chain With a Dumb Terminal

RS-485 3-6
RS-485 Multidrop System

CHAPTER 4 Command Set

Table of Commands 4-7
User Commands
Error Messages

4-8

4-1

6

3-3

3-4

3-6

3-7

CHAPTER

5

Setup

Information and Command

Command Syntax 5-2
Setup Hints 5-13

CHAPTER 6 Digital

Digital Outputs
Digital Inputs

110

Function

6-1

6-3

Events Counter 6-4
Alarm Outputs 6-5
On-Off Controller
Setpoi nt

CHAPTER 7 Power

6-9

Supply

CHAPTER 8 Troubleshooting
CHAPTER 9 Calibration
Appendix A ASCII TABLE

Appendix
Appendix
Appendix D

B

M1400

C

M1500

M1600

Data

Sheet
Data Sheet
Data Sheet

6-5

3

WARRANTY

MetraByte Corp. warrants your
parts, materials and workmanship under normal use and service
one year
any defective unit brought to its attention during that period.

MetraByte
be suitable to your purpose.

Some states
ties,

In

no event will MetraByte Corp. be liable to you for any damages, including
profits,
the use or inability to use this product, even
MetraByte
any claim

MetraByte
future patents

Some

consequential damages
you.

so

the

states

from

the date of delivery, and will repair

Corp

makes no implied warranty that the

do

not attow the exclusion of implied warranties or limited warran-

above

lost

savings, or other incidental

dealer

by

Corp.

may not apply to you.

has

been advised

any other party.

cannot assume responsibility for infringement

or

other third party rights resulting from the use of these

do

not allow the limitation or exclusion

so

M1000

the above limitation or exclusion may not apply to

series module

to

be free from defects in

for

or

replace, at its sole option,

M1

000

series modules will

or

consequential damages arising out

if

of

the possibiIity

MetraByte or

of

such damages, or for

of

liability for incidental

an

of

a

authorized

present

products.

period

of

lost

of

or

or

This

except

or

original purchase price.
extend the original warranty period
repaired

warranty is void

by

MetraByte or has been subjected

accident. In no case

or

replaced by MetraByte.

if

the product has been repaired

shall

The

aforementioned provisions

or

altered

to

misuse,

MetraByte's liability exceed

of

any product which has been

negligence,

do

the

not

4

WARNING

The circuits and software contained
are proprietary to MetraByte Corporation. Purchase
products does not transfer any rights
circuits or software used
decompiling

of

the

software program

in

these products. Disassembling or

Reproduction of the software program

As

explained

from

the outside of the

in

the setup section, all setups are performed entirely

M1000

module. There

in

the

MI000

or

grant any license

is

explicitly prohibited.

by

any means is illegal.

is

Series modules

of

these

to

the

no need to open
the module because there are no user-serviceable parts inside.
Removing the cover or tampering with, modifying, or repairing

by

unauthorized personnel will automatically void the warranty.
MetraByte

RETURNS

When returning products for any reason, contact the factory and request

Return Authorization

Authorization Number on

recommends

should not

is

not responsible for any consequential damages.

Number

the

that you insure the product

be

returned collect

and

outside

as

they will

shipping instructions. Write the Return

of

the shipping

for

value

not

be

accepted.

box.

prior

MetraByte

to

shipping. Items

strongly

a

5

CHAPTER

1

GETTING STARTED

Default

AII

Read Only Memory) to store setup information and calibration constants. The
EEPROM replaces the usual array of switches and pots necessary to specify
baud rate, address, parity, etc. The memory is nonvolatile which means that the
information is retained even
never necessary to open the module case.

The
setup parameters may be configured remotely through the communications port

without having to physically change switch and pot settings. There is one minor

drawback in using EEPROM instead

the setup information in the module. It is impossible to tell

module what the baud rate, address, panty and other settings are.
very difficult
baud rate are unknown.
pin labeled DEFAULT
in a known communications setup called Default Mode.

The Default Mode setup is:

Mode

M1000 modules contain an EEPROM ( Electrically Erasable Programmable

if

EEPROM

to

power is removed.

provides tremendous system flexibility since

of

switches; there is no visual indication of

establish communications with a module whose address and

To

overcome this difficulty, each module has an input

*.

By connecting this pin to Ground, the module is placed

300

baud, no parity, any address

No

batteries are used

all

of

just

by

is

recognized.

so

it is

the module's

looking

at the

It

could be

Grounding the

EEPROM. The setup may be read back with the Read Setup
determine all
commands are available

A

module in Default Mode will respond to any address except the four identified
illegal values
command for proper responses. The ASCII value of the module address may
be read back with the
character is to deliberately generate an error message. The error message
outputs the module's address directly after the

Setup information in a module may be changed at
command. Baud rate and parity setups may be changed without affecting the

Default values

the module automatically performs a program reset and configures itself

baud rate and panty stored in the setup information.

The Default
terminal

In most cases, a module in Default Mode may not be used in a string with other
modules.

or

DEFAULT

of

the

(NULL,

of

Mode

computer for the purpose

CR,

300

baud and no parity.

is

intended

pin does not change any of the setups stored in

setups stored in the module. In Default Mode,

as

usual.

$,

#).

A

dummy address must be included in every

RS

command. An easy way to determine the address

to

be used with a single module connected to

(RS)

command

"?

prompt.

will

with the Setup

When

of

identifying and modifying setup values.

the

DEFAULT*

pin is released,

(SU)

to

to

all

the

a

RS-232 &

RS-485

Quick

Hook-Up

Software is not required to begin using your

MlOOO

module.

We

recommend

that you begin to get familiar with the module by setting it up on the bench.

Start by using a dumb terminal
Make the connections shown in the quick hook-up drawings, Figures

Put

the module in the default mode by grounding the Default* terminal. Initialize

the terminal communications package

"terminal" mode. Since this step varies from computer

or

a

computer that acts like a dumb terminal.

on

your computer to put

to

computer, refer to your

1.1

or

it

into the

1.2.

computer manual for instructions.
Begin by typing

$1RD

and pressing the Enter

or

Return key. The module will
respond with an followed by the data reading at the input. The data includes
sign, seven digits and a decimal point.

For

example,

if

you are using

a

thermocouple module and measuring room temperature your reading might be

*+00025.00.

preset

at

to the section

All

modules are shipped from the factory with a setup that includes a channel

address

The temperature reading

will

initially be in

"C

which has been

the factory. Once you have a response from the module

on

commands and get familiar with the command set.

of

1,

300

baud rate,

no

linefeeds, no parity, alarms

off,

you

can turn

no echo

and

2

character delay. Refer to the setup section to configure the module to your

application.

.

1-2

+

10

to

Power

-

Q

1k

41

Figure

+30

Vdc

Supply

+Q

1.1

RS-232C

7

tB

@

8

8

@

-@

8

~B

8

3

Quick

M

VOLTAGE

RS-232C

SIU

Hook-up

1121

0586

i"

RS-485

RS-485

An
evaluation purposes. This connection

and

hook-up. This connection wilI work provided the
current limited to less than
than
requirement. With this connection, characters generated
echoed back.
should

If

the current limiting capability

100R to1

In

some

ground through a 1

Quick

RS-485

should never be

OV.

All

be

turned

ki2

rare cases it may be necessary to connect the

Hook-up

module may be easily interfaced to an

terminals that use

To avoid double characters, the local echo on the terminal

off.

resistor

OOrZ

to

a

RS-232

used

in

series with the

for a permanent installation. Figure

50

to

1

kn

resistor.

ma

1488

of

port

is

and the

and

the

RS-232C

RS-232

only suitable for benchtop operation

RS-232C

1489

output.

RS-232C

receive threshold

style interface IC's

output is uncertain, insert

RS-232C

transmit output is

by

the terminal will be

module's

terminal for

1.3

shows

is

greater

will

satisfy this

DATA

the

a

pin to

+

10

to

Power

+30

Vdc

Supply

Figure

1.3

RS-485

Quick

Hook-Up

with

RS-232C

Port.

1-4

CHAPTER

2

FUNCTIONAL

A

functional diagram of a typical MetraByte sensor module is shown in Figure

2.1

. It is a useful reference designed

and to explain the function
The first step is to acquire the sensor signal and convert it

Figure
the analog-to-digital converter
internally and

The full-scale output

(TS)

the
the unit with a laboratory standard reference applied

The trimmed data now flows into either

performed automatically by the microprocessor after every

filter selection depends on the difference

previous data stored in the output
digit from the

large signal filter is selected.

signal filter is used.

2.1,

all the signal conditioning circuitry has been lumped into one block,

is

transparent

command. The TS command adjusts calibration values stored internally in

EEPROM.

The TS command should only be used to trim the accuracy of

AID

differs from the old output

of

of

many of the modute's commands.

(ND).

to

the user.

the

AID

converter may be trimmed using the Trim Span

If

the change is less than

to

illustrate the data path in the module

Autozero and autocalibration is performed

to

of

two digital filters. The filter selection is
of

the current

data

register.

If

data

by more than

DESCRIPTION

to

digital data. In

the sensor input.

A/D

conversion. The

A/D

output data and the

the least significant decimal

10

counts, the

10

counts, the small

The two-filter system allows for different degrees of filtering depending on the

rate

of

the input change. For steady-state signals, the small-signal filter

averages out noise and

output. The large-signal filter
signals. The time constants for the two filters can

with the Setup

memory. Typically, the srnall-signal filter is set to a larger time constant
large-signal fitter. This gives very good noise rejection along with fast response

to step inputs.

The MetraByte modules allow for user selectable output scaling in
temperature data. This selection is depicted in Figure
the digital filters. The defauk scaling
converted to
position
Setup
temperature applications, the

The scaled data is
obtain the final output value. The output offset is controlled by the user and
serves many useful purposes. The data in the Output Offset Register may be

is

controlled by a bit in the setup

(SU)

(SU)

OF

by feeding the data through a conversion routine. The switch

command. The scaling selection is nonvolatile. For non-

summed

small

is

command.

"c

position should always be selected.

with data stored in the Output Offset Register

input

activated by step changes

changes

The filter values are stored in nonvolatile

to

give a stable steady-state

or

very noisy input

be

specified independently

than

"C

or

2.1

as a switch following

in

the modules

data

and may

is

OC,

but this may be

be

changed with the

"F

the

on

to

used to trim any offsets caused by the input sensor.

undesired signal such

adjust the output to any desired value by loading the appropriate data value in

the offset register. The data in the offset register

as

a tare weight. The

Trim

is

It

may be used to null out

Zero

(TZ)

nonvolatile.

command is used to

The output offset may also be modified using the Set Point

data

loaded into the register. The Set Point command specifies a null value that is
subtracted from the input data. The output reading becomes a deviation value
from the downloaded setpoint. This feature
described in the digital

The value stored in the

(RZ)

sign changed. The output register may
command.

The output data may be read with the Read Data (RD) command. In some
cases when a computer
same data value several times before it

To

(ND)

the New Data Flag is cleared. The flag is set each time the output

is

until the flag

value specified

command. Data loaded in with the

guarantee that the same

command may be used. Each time an RD or ND command is performed,

loaded as the result

is

set before it outputs the data reading.

by

I/O

offset

of

the

SP

section

register may be read back using the Read Zero

is

used

data

a

new

command is multiplied

is

very useful in on-off controllers as

of

this manual.

SP

command will be read back with the

be

reset to zero with the Clear Zero

as

a host,

is

not read more than once, the New Data

A/D

it

may be possible to read back the

is

updated with a new

conversion. The ND command will wait

(SP)

command. The

by

-1

before being

A/D

conversion.

data

(CZ)

register

The remainder of Figure

Digital
general-purpose digital inputs and outputs. These functions are described in
detail in the Digital I/O section.

The heart of the alarm section consists of

high and low alarm limit values. These registers may be down-loaded with data
values by using the HI and
with the same data format that is used with the output data. The high and
alarm registers are nonvolatile
down. The values contained in the alarm registers may be read back at any
time with the Read High (RH) and Read tow (RL) commands.

The

output data. The result

used as control outputs. The high alarm is turned on when the output data

exceeds the high limit value. The low alarm is activated
than the low alarm value. Each alarm has two user selectable modes, either

Momentary

alarm condition is met;

off.

I/O

section. It consist of a versatile alarm function, an event counter and

data

held in the alarm registers

(M)

or Latching

Conversely, when latching alarms are activated, they remain on even

2.1

depicts several functions known collectively

two

registers that are used to store

LO

alarm commands. The alarm values are loaded

so

they

will

not be lost when the unit

is

continually compared with the calculated

of

the comparison is used

(L).

Momentary alarms are activated only while the

if

the output data returns within limits, the alarm is turned

to

trip alarms that may be

if

the output data

as

is

powered

is

less

if

the

low

the

2-2

output data returns within limits. Latching alarms are turned
Alarms (CA) command

or

if

the opposite alarm limit is exceeded.

off

with the Clear

The state

the

alarm outputs may be used to activate digital outputs on the module

connector

the number

are shared with the general purpose digital output bits DO0 and
connect the alarm outputs
used. The connector pins may be switched
outputs using the Disable Alarms

nonvolatile.

The general-purpose digital outputs are open-collector transistor switches that

may be controlled by the host with the Digital Output
designed to activate external solid-state relays to control AC or
circuits. The output may also be
The number
being the maximum.

The Digital Input (DI) command
input pins DIO-D17. The digital inputs are used
other devices. They are also useful
limit switches. The number of digital inputs vanes with the module type.

of

the alarms may be read with the Digital Input

to

turn

on

alarms or to perform simple control functions.

of

terminals required on the module connector, the alarm outputs

to

the connector, the Enable Alarm (EA) command is

back

(DA)

used

of

digital outputs available depends on the module type, with eight

is

used

command. The ENDA selection is

to interface to other logic-level devices.

to

sense the logic levels

to

sense the state

to the general-purpose digital

to

read

(DI)

(DO)

command. They are

logic

of

command. Also,

To

on

levels generated by

electro-mechanical

help limit

D01.

DC

the digital

To

power

The DIO input is shared with the input to the Event Counter. The Event Counter

is

used to accumulate the number

the DWEV connector pin. The counter

(decimal) events and may be read with the Read Events
counter input is filtered and
free input for mechanical switches. The counter value may be zeroed with the
Clear Events

(CE)

command.

uses

of

positive transitions that have occurred on

can

accumulate up

a

Schmitt-trigger input tc provide a bounce-

to

9999999

(RE)

command. The

2-

3

7

W

a

'I

W

0

I

a

a

N

c

L

VI

Y

N

u

II

1

a

t

I

2-4

--%-

w

u

4

..

WP

CHAPTER

3

COMMUNICATIONS

Introduction

The M1000 series of interface modules has been carefully designed to be easy

to

interface to all popular computers and terminals.
from the modules are performed with printable
the information to

languages such as

as

RS-232C, no special machine language software drivers are necessary for
operation. The modules car, also be connected to auto-answer modems for
long-distance operation without the need for a supervisory computer. The

format also makes system debugging easy with a dumb terminal.

be

processed with string functions common

BASIC.

For computers that support standard interfaces such

All

ASCII

communications to and

characters.

This

to

most high-level

allows

ASCII

The MetraByte system

a communications port with a single 4-wire cable.
may

be

strung together on one cable; 124 with repeaters. A practical limit for
232C
communicate with the host on a polling system; that

to

never initiate
protocol must be strictly observed
errors.

Communications to the
command codes such
description
commandresponse sequence would

A

received. The host may not initiate a new command until the response from
previous command
communications collisions. A valid response

units is about ten, although a string of 124 units

its own unique address and must be interrogated by the host. A module can

a

of

all commands is given

Command:

Response:

commandresponse sequence

is

designed to allow multiple modules to be connected to

Up

to

32

RS-485

is

possible. The modules

is,

each module responds

communications sequence.

to

avoid communications collisions and data

Mi

000

modules

as

RD to Read Data from the analog input. A complete

$1

RD

*+00123.00

is

is

complete. Failure to observe this rule will result in

is

in

the Command Set section.

look

like this:

not complete until a vatid response is

can

A

simple command/response

performed with two-character ASCII

be in one of three forms:

modules

RS-

A

typical

a

1)

a normat response indicated by a

2)

an error message indicated by a

3)

a communications time-out error

When a module receives a valid command, it must interpret the command,

perform the desired function, and then communicate the response back
host. Each command has an associated delay time in which the module is busy

calculating the response.

appropriate amount

of

If

the host does not receive a response in an

time specified in Table

'

' * '

'?

prompt

'

prompt

3.1,

to

the

a communications time-out

error has occurred. After the communications time-out it is assumed that

response data is forthcoming. This error usually results when an improper

command prompt or address is transmitted.
The following table lists the timeout specification for each command:

Mnemonic Timeout

DI,

DO,

RD

,WE

ND

All

other commands

10

ms.

See text

100

ms.

no

Table
This timeout specification indicates the turn-around time from the receipt

command to when the module will start to transmit a response.

RS-232C

RS-232C

transfer between computing equipment.

interface to virtually all popular computers without any additional hardware.
Although the
equipment to a computer, the MetraByte system allows for several modules to
be connected in a daisy-chain network structure.

The advantages offered by the

3.1

Response Timeout Specifications.

is

the most widely used communications standard for information

RS-232C

RS-232C

1)

widety used by all computing equipment

2)

no additional interface hardware

3)

separate transmit and receive lines ease debugging

4)

compatible with dumb terminals

standard

RS-232C

is

designed to connect a single piece of

standard are:

in

most cases

versions of the

M1000

of

will

a

However,

1)

2)

3)

4) greater communications delays in multiple-module systems

5) less reliable-loss

6)

7)

3-2

RS-232C

low noise immunity

short usable distance

maximum baud rate - 19200

wiring is slightly more complex than RS-485

host

software must handle echo characters

suffers from several disadvantages:

-

50

to

200

feet

of

one module results in no communications

Single

Module

Connection

Figure
Use the Default Mode to enter the desired address, baud rate, and other setups
(see Setups). The use of echo

the communications line.

Multi-party

RS-232C is not designed to be used in a multiparty system; however the

modules can be daisychained to allow many modules to be connected to
single communications port. The wiring necessary to create the daisy-chain
shown in Figure 3.1. Notice that starting with the host, each Transmit output
wired
sequence must be followed until the output of the last module in the chain is
wired to the Receive input of the host.
the same baud rate and must echo ail received data (see Setups). Each module

must be setup with its own unique address

(see Setups). In this network, any characters transmitted by the host are

received by each module

information
the commands given by the host are examined by every module.
the chain

by transmitting the response

be ripple through any other modules

destination, the Receive input of the host.

1.1

shows the connections necessary to attach one module

is

not necessary when using a single

Connection

to

the Receive input

is

echoed back

is

correctly addressed and receives a valid command, it will respond

of

the next module in the daisy chain. This wiring

All

modules in the chain must be setup to

to

avoid communications collisions

in

the chain and passed on to the next station until the

to

the Receive input

on

the daisy chain network.

in

the chain until it reaches its final

of

the host. In this manner all

The

to

module

If a module in

response

a

host.

Ml000

data

on

a

is

is

will

The daisy chain network must be carefully implemented to avoid the pitfalls

inherent in its structure. The daisy-chain is a series-connected structure and any

break in the communications link will bring down the whole system. Several

rules must be observed

1.

All

wiring connections must be secure; any break in the wiring, power,
ground, or communications will break the chain.
plugged into their respective connectors.

2.

All

modules must be setup for the same baud rate.

3.

All

modules must be setup for echo.

to

create a working chain:

All

modules must be

3-3

I

+10

+30Vdc

to

RS-232

+

-

To

+Vs

Figure

Software

If

the host device
messages on its Receive input along with the responses from the module. This
can usually be handled by software string functions by observing that a module
response always begins with a
return.

A

properly addressed

characters

receiving the carriage return, the module will immediately calculate and transmit
the response
characters that appear on its receive input. However,
during this computation period, it will
buffer.

the

module. This situation will occur

character on the command carriage return. In this case the linefeed character
will be echoed after the response string has been transmitted.

Considerations

in

the command including the terminating carriage return. Upon

to

This

character will be echoed after the response string is transmitted

3.1.

RS-232

is

a

computer, it must be able to handle the echoed command

MI000

the command. During this time, the module will not echo any

Da

sy

Chain

' * '

or

' ? '

module in a daisy chain will

be

stored in the module's internal receive

if

the host computer appends a linefeed

Network

character and ends with a carriage

if

a

character is received

echo

all of the

by

The daisy chain also affects the command timeout specifications. When a

module in the chain receives a character
character through the module's internal UART. This method

more reliable communications since the UART eliminates any slewing errors
caused

3-4

by

the transmission lines. However, this method creates a delay in

it

is echoed by retransmitting the

is

used

to

provide

propagating the character through the chain. The delay

necessary to retransmit one character using the baud rate setup in the module:

is

equal to the time

Baud Rate
300 33.30 ms.

600

1200 8.33
2400
4800

9600

One delay time is accumulated for each module in the chain.
four modules are used in a chain operating at
delay time is 4 X

listed in Table

For

modules with RS-232C outputs, the programmed communications delay

specified in

NULL character
This results in a delay
specified in the setup data, this sequence is repeated. Programmed
communications delay
each module in the chain

the

8.33

3.1

to calculate the correct communications time-out error.

setup data (see Setup section)

(00)

Delay

16.70

ms.

ms.

4.1

7

ms.

2.08

ms.

1.04

ms.

For

example,

1200

ms.

=

33.3

ms.

This

time must be added to the times

is

followed by an

of

two character periods.

is

seldom necessary in an RS-232C daisy chain since

adds

one character of communications delay.

idle

line condition for

baud, the accumulated

implemented by sending

one

character time.

For

longer delay times

if

a

Changing

It

is possible to change the baud rate of an RS-232C daisy chain on-line. This

process must be done carefully

module

reset can be caused by the Remote Reset
power interruptions.

using the Read Setup
for the same baud rate.

power to the modules. This generates a power-up reset in each module and

loads in the new baud rate.

com m u nications.

8aud

1.

Use the Setup

in

the chain. Be careful not to generate a reset during this process.

2. Verify that

3.

Remove power from

4. Change the host

Rate

to

avoid breaking the communications link.

(SU)

command

all

the modules in the chain contain the new baud rate setup

(RS)

command. Every module in the chain must be setup

all

the modules for

baud

to

change the

(RR)

at

rate to the

bmd

command, a line break,

least

new

rate setup

10

seconds. Restore

value

and

on

each

check

A

or

5.

Be sure to compensate

of

the new baud rate.

for

a

different communications

delay

as

a result

~~

Using A Daisy-Chain

A dumb terminal can be used to communicate to a daisy-chained system. The
terminal is connected in the same manner
Any commands typed into the dumb terminal will be echoed by the daisy chain.

To

avoid double characters when typing commands,
duplex mode or turn
command echo.

RS-485

RS-485
multidropped systems that can communicate
distances. RS-485
of wires switching from

handle common mode voltages from
them ideal for transmission over great distances. RS-485 differs from RS-422
using one balanced pair of wires

RS-485 system cannot transmit and receive at the same time it is inherently a

half-duplex system.

is

a

recently developed communications standard to satisfy the need for

With

off

is

similar to RS-422 in that

A

Dumb

the

local

0

to

5 volts to communicate

Terminal

echo. The daisy chain will provide the input

-7V

for

both transmitting and receiving. Since an

as

when using a computer as a host.

set

the terminal

at

high data rates over long

it

uses a balanced differential pair

to

+12V

data.

without

RS-485 receivers can

loss

of

data, making

to

full

by

RS-485 offers many advantages over

1)

balanced line gives excellent noise immunity

2)

can

be

used

to

to

communicate with

3)

communications distances up

4) true multidrop; modules are connected in parallel

5)

modules can be disconnected without breaking communications

6)

up to

32

modules

7)

no

communications delay due to multiple modules

8) simplified wiring using standard telephone

Of course, RS-485 does have its disadvantages. Very few computers or
terminals have built-in support for
available
become available
system usually requires the extra expense

Metra8yte

RS-485.For systems that require more than
distances,

for

the

IBM

as

Cop.

or

offers interface converters to convert RS-232C and

high speed, RS-485

on

one

PC

and compatibles and other RS-485 equipment will

the standard gains popularity. This means that an

RS-232C:

M1

000 modules at 38400 baud

to

10,000

line; 124 with repeaters

feet.

cable

this

new standard. Interface boards are

of

an interface.

a

few modules, long wiring

is

recommended

RS-485

RS-422

to

3-6

Host

RS-485

..

-

DO(G)

GNDlB>

T

B=

Black

R=

Red

G=

Green

v=

Yellow

up

ra

10,000

Feet

+

Figure

3.2.

RS-485

MuItidrop Network.

I

RS-485

Figure
Notice that every module has a direct connection
number
remaining modules. Each module must be setup with a unique address and the
addresses can be

to

module are labelled with notations
designate the

This color convention

installation.
match the labeled pins with the wire cotor

Multidrop

3.2

illustrates the wiring required for multiple-module

of

modules may be unplugged without affecting the operation of the

avoid bus conflicts (see Setup). Also note that

colors

Label Color

(6)

GND

(R)

v+

(G)

DATA* Green

(Y)

DATA Yellow

If

System

in

any order.

used on standard 4-wire telephone cable:

Black

Red

is

used on all MetraByte

standard 4-wire telephone cable

All

RS-485

(B),

(R),

to

guarantee correct installation.

modules

(G),

RS-485

is

to

must

the

and

used,

RS-485

the host system. Any

be setup for no echo

connector

(Y).

equipment to simplify

it

is only necessary

pins

These notaticns

system.

on each

to

The notation

of DATA (negative true).

To minimize unwanted reflections

arranged
structures

500

feet total, the end

connected between DATA and DATA*.

as

of

'

'

on the label DATA* is simply used to indicate the complement

on

a

line going from one module

the

transmission line should be avoided. For wire

of

the

line

should

the transmission line, the

to

the next. 'Tree'

runs

be terminated with

a

100

bus

should be

or

random

greater than

ohm resistor

3-7

Special care must be taken with very long busses (greater than

ensure error-free operation. Long busses must be terminated as described

above. The use of twisted cable for the DATA and DATA* lines will greatly

enhance signal fidelity. Use parity and checksums along with the

commands to detect transmission errors. In situations where many modules are

used on a long line, voltage drops in the power leads becomes an important

consideration. The

common reference for the transmission line receivers in the modules. Voltage

drops in the
The receivers are rated

reliable operation, the common mode voltage should be kept below -5V. The

resistance of

ohms per

Using Ohm's Law, the maximum allowable resistance in the
within the -5V. common-mode condition is

results
calculations can be reduced to a general rule-of-thumb by taking the number

modules on the bus and multiplying it by the
number must be less than the number given in the following Table

in

Wire Gauge Maximum modules X feet

GND

20

1000

a maximum bus length

GND

leads appear

gauge wire commonly used

feet. The maximum current

wire is used both as a power connection and the

as

a

common-mode voltage to the receivers.

for a maximum

of

of

6670 feet for a single module. These

-7V.

draw

66.7

bus

of common-mode voltage. For

in

telephone cable is about

from a single module is 75 ma.

ohms. For

length in feet.

20

1000

'#'

GND

gauge wire this

The

:

feet) to

form of

lead to be

resultant

all

10

of

22

20

18
Communications
All

M1000

units of communications delay after a commacb has bee:: received (see
section). This delay is necessary when using host computers that transmit
carriage return as a carriage return-linefeed string. Without the delay, the

linefeed character may collide with the first transmitted character from the
module, resulting in garbled data.
return as a single character, the delay may be set to zero to improve

communications response time.

modules with RS-485 outputs are setup at the factory to provide two

Delay

4000

6000

i

0000

If

the

host

computer transmits a carriage

Setup

a

CHAPTER

4

COMMAND

The

M1000

control all module functions. A command must be transmitted to the module by
the host computer

A

module can never initiate a communications sequence.

mands exists to exploit the full functionality

commands and a sample format for each command is listed in Table

Command

Each command message from the host must begin with a command prompt
character to signal to the modules that a command message is to
are two valid prompt characters; a dollar sign character
short response message from the module.
amount of data necessary
character is the pound sign character

long

response format will be covered a little later).

The prompt character must be followed by
identifying the module to which the command is directed. Each module
attached to a common communications
address
addresses are assigned by the user with the Setup
resub, use printable

$41)

are the best choices for address characters.

modules operate with

or

terminal before the module will respond with useful data.

Structure

to

complete the command. The second prompt

so

that commands may be directed to the proper unit. Module

ASCII

characters such as

a

simple commandhesponse protocol to

A

variety of com-

of

the modutes.

($)

A

short response is the minimum

(#)

which generates long responses (the

a

single address character

port

must be setup with its own unique

(SU)

'1'

(ASCII

A

list of available

4.1.

follow.

is used to generate a

command. For best

$31)

or

'A'

SET

There

(ASCII

The address character is followed

the function to be performed by the module.

listed in Table
described in full later in this section. Commands must be transmitted as upper­case characters.

A

two-character checksum

user option. See 'Checksum' section below.

All

commands must be terminated
(In all command examples in this text the Carriage Return is either implied
denoted by the symbol

Data

Structure

Many commands require additional data values to complete the command

definition as shown in the example commands

necessary

descriptions.

4.1

along with a shcrt

may

'CR'.)

for

these commands is described

by

a

two-character command which identifies

All

of

the available commands are

function definition.

be appended to

by

a Carriage Return character

in

in

any

command message as a

Table

full

in

All

commands are

(ASCII

4.1.

The particular data

the cornpIete command

$OD).

OF

The most common type
data. Analog data is always represented in the same format for
the

MlOOO

consisting of a sign, five digits, decimal point, and two additional digits. The
string represents a decimal value in engineering units.

series. Analog data is represented as a nine-character string

Examples:

of

data used in commands and responses is analog

all

models in

-1-1

2345.68

+00100.00

-00072.1

0

-00000.00

When using commands that require analog data as an argument, the full nine­character string must be specified, even though some digits may not be
significant. Failure

Analog data responses from the module will always be transmitted in the nine­character format. This greatly simplifies software parsing routines since all

analog

data

is

to

do this

in the same format for

will

result in a SYNTAX

all

module types.

ERROR.

In many cases, some
instance,
resolution.

-1-00123.00

nificance in this particular model. However, the data format

to in order to maintain compatabitity with other module types.
The maximum computational resolution of the rnodute is

than the resolution that may be represented by an analog data variable. This

may lead to round-off errors in
be sto:ed in a

Command:

the

M1300

A

typical analog data value from this type of module could be

. The two digits to the right of the decimal point have no sig-

M1

OCO

$1

of

the digits in the analog data may not be significant. For

thermocouple input modules feature 1 degree output

is

always adhered

16

bits, which

some

module using the 'HI' arnmand:

HI+i2345.67M

cases. For example, an alarm value may

is

less

Response:

The alarm value may then

Command:

Response:

It appears that the data read back does not match the value that
saved. The error is caused by the fact that the value saved exceeds
computational resolution of the module.
appears when large data values saved in the module's

In

most practical applications, the problem is nonexistent.

$1

RH

*+12345.60M

be

read

back

with the Read High

This type of round-off error only

(RH)

command:

EEPROM

was

originally

the

are read back.

Overload values of analog data are represented by 49999.99 and -99999.99

4-2

-