Tektronix M1700 Series of Digital I/O to Computer Interfaces Users Guide

M1700

Series of Digital I/O To Computer Interfaces 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: 440-248-6168

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

Sales Ofﬁces:BELGIUM: Bergensesteenweg 709 • B-1600 Sint-Pieters-Leeuw • 02-363 00 40 • Fax: 02/363 00 64

CHINA: Yuan Chen Xin Building, Room 705 • 12 Yumin Road, Dewai, Madian • Beijing 100029 • 8610-6202-2886 • Fax: 8610-6202-2892 FINLAND: Tietäjäntie 2 • 02130 Espoo • Phone: 09-54 75 08 10 • Fax: 09-25 10 51 00 FRANCE: 3, allée des Garays • 91127 Palaiseau Cédex • 01-64 53 20 20 • Fax: 01-60 11 77 26 GERMANY: Landsberger Strasse 65 • 82110 Germering • 089/84 93 07-40 • Fax: 089/84 93 07-34 GREAT BRITAIN: Unit 2 Commerce Park, Brunel Road • Theale • Berkshire RG7 4AB • 0118 929 7500 • Fax: 0118 929 7519 INDIA: Flat 2B, Willocrissa • 14, Rest House Crescent • Bangalore 560 001 • 91-80-509-1320/21 • Fax: 91-80-509-1322 ITALY: Viale San Gimignano, 38 • 20146 Milano • 02-48 39 16 01 • Fax: 02-48 30 22 74 JAPAN: New Pier Takeshiba North Tower 13F • 11-1, Kaigan 1-chome • Minato-ku, Tokyo 105-0022 • 81-3-5733-7555 • Fax: 81-3-5733-7556 KOREA: 2FL., URI Building • 2-14 Yangjae-Dong • Seocho-Gu, Seoul 137-888 • 82-2-574-7778 • Fax: 82-2-574-7838 NETHERLANDS: Postbus 559 • 4200 AN Gorinchem • 0183-635333 • Fax: 0183-630821 SWEDEN: c/o Regus Business Centre • Frosundaviks Allé 15, 4tr • 169 70 Solna • 08-509 04 679 • Fax: 08-655 26 10 SWITZERLAND: Kriesbachstrasse 4 • 8600 Dübendorf • 01-821 94 44 • Fax: 01-820 30 81 TAIWAN: 1FL., 85 Po Ai Street • Hsinchu, Taiwan, R.O.C. • 886-3-572-9077• Fax: 886-3-572-9031

4/02

User Guide

for

the

M

1700

Digital

Series

I/O

To

Computer Interfaces

R

vision

Copyright Keithley MetraByte

Pan

A

Number:

-

June

Of

1991

24403

Corp.

1991

All

products manufactured

materials

the

warranty

This

original

period

warranty

and

worksmanship for

purchaser.

will,

does not apply

by

Any product

at

the

option

Warranty Information

Keithley MetraByte

a

period

of

that

is

of

Keithlq

to

products

damaged

are

one

year

found

to

MetraByte,

warranted

horn

be

by

improper

Warning

the

date

defective

be

repaired

against

of

delivery to

within

or

use.

defective

the

replaced.

gdthlep

use

of

level

of

Information

reliable.

for

of

or otherwise under

However,

the

use

third

parties that may result

Note:

MetraByte"

Basic"

Is

MetraEyte

this

product.

rcliabiiity

furnished

of

such information nor

is

a

trademark

p8sumes

This

suitabIe

by

the

KeiMey

any

patent

trademark of

of

Dartrnouth

no

liability

product

for

is

not designed with components

use

in

life

Disclaimer

Keithley MetraByte

MetraByte

from

rights

Keithley

Corporation assumes

for

any

its

use.

of

Keithley

MehaByte Corporation.

College.

for

support

is

believed

damages

consequent

or

critical

to

be

accurate

no

infringements of patents

No

license

is

granted

MetraByte

Corporation.

to

the

of

applications.

and

responsibility

or

other

by

implication

a

rights

IBMQ

is

a

registered

PC.

XT,

AT,

PS/2,

tional Business Machines

Microsoft@

Turbo

is

t3

is

a

bademark

and

a

registered trademark

registered trademark of Borland

oflnternational Business Machines Corporation.

Micro

Channel Architecture@

Corporation.

of

-

are trademarks

Microsoft Corporation.

International

iv

-

of

Intema-

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: (440) 248-6168

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.

Digital Input Digital Output Events Read & Clear (EC) Identification (ID) Initial Value Read Assignment (RA) Read Assignment Bit (RAB) Read Assignment Position (RAP) Read Bit Read Position (RP) Read Continuous Mode Read Continuous Timer (RCT) Read Input Address (RIA) Read Data (RD) Read Identification Read Initial Value (RIV) Read Input Sit Read Input Position (RIP) Read Setup Remote Reset

Read Watchdog Timer Setup Command Watchdog Timer Write Enabte

Error Messages

Address Error

Badchecksum., Command Output

Parity Error Syntax Error Value Error Write Protected

(DI)

.................................

(DO)

................................

.................................

(IV)

.................................

..............................

(RB)

...................................

................................

(RCM)

.................................

(RID)

.............................

(RIB)

...............................

(RSU)

Error

....................................

................................

(RR)

...............................

(RWT)

(SU)

..............................

(wr)

..............................

(WE)

................................

...................................

................................

.................................

...................................

..................................

..........................

.........................

............................

...........................

........................

.........................

............................

..........................

4-10 4-10

4-11 4-11 4-11 4-12 4-12 4-12 4-13 4-13 4-13 4-13 4-13 4-14 4-14 4-14

4-15

4-15 4-15 4-15 4-16 4-16 4-16 4-17 4-17 4-18 4-18 4-18 4-18 4-19 4-19 4-19 4-19 4-19 4-19

CHAPTER

5:

SETUP INFORMATION

Command Syntax B~el Byle2

Bytes

Setup Hints

SlOOO

..........................................

Linefeeds

Panty

Baud Rate

B~e3

B~e4

........................................

3

&

4

.......................................

........................................

Echo

.......................................

Delay

........................................

Event Counter Filter

Word Length

.......................................

Software

I

SETUP

COMMAND

...................................

......................................

.....................................

......................................

..............................

..................................

....................................

.

vi-

5-1

5-2

5-3

5-3 5-4

5-5

5-6

5-8

5-9

Contents

CHAPTER

APPENDICES

Appendix Appendix Appendix C

6:

A B

CONTINUOUS lNPUT/OUTPUT

Continuous Output Continuous Input Continuous Inputloutput Commands Continuous Output Trigger Signal Applications

A) Timer Mode

B)

Timer Mode With Outputs

C) Edge-Trigger Mode With

D) E)

Change Mode

F)

Change Mode With Multiple Modules

G)

H)

I)

8idirectionaI Continuous InpuVOutput

J)

Multiple Outputs

Continuous

ASCII

Mi770 64 Mi750

.......................................

Continuous Output Daisy-Chain With Host

Continuous Input Multiple Continuous Input/Output

Input Protocol Notes

Table

Channel

24-Channel

...................................

....................................

..........................

....................................

...........................

Host

..................................

Mode

................................

............................

...........................

I/O

Board

Digital

110

Board

6-1

6.1

.........................

..........................

..................

.....................

.......................

.....................

6.1

-6-2

6.2

-6-3

6.4

-6-6

6.7

-6-9 6-10 6-12 6-13

6-13

6-14

.

vii

.

Chapter

1

Introduction

The Keithley MetraByte 1700 Series computer monitoring and control of devices through solid state relays or TTL signals. The status of inputs and outputs is communicated format using

With the Keithley MetraByte 1700 series the user can control digital inputs and outputs individually or all at once. Any channel may be designated as an input or output by the user. Many industrial applications require a safe start-up condition to prevent accidents at critical points in the process.The onboard nonvolatile

EEPROM memory stores the user-specified initial condition (input or output) each channel; thereby eliminating the need when power is applied

1700 series may be setup in special modes which allow them

The communicate without being polled by a host computer. Collectively these modes are called Continuous InpuVOutput Modes. In many applications the burden on the host may be greatly simplified and in some cases the host may be eliminated

altogether.

The Keithley MetraByte 1700 series include:

M1711/1712

M1750

M1770

Getting

The instructions

use

the MI711 & Mi712 in the figures.

appropriate appendix for instructions on getting started.

RS-232C

<!5

24

64

Started

in

or

RS-485

or

restored.

channel channel channel

this chapter cover all

110

I/O

of

Digital

serial communications.

modules. board. board.

110

to Computer Interfaces provide

for

software initialization routines

1700

models; however, for simplicity we

If

you have an M1700 board

to

the host in ASCII

see

of

to

the

Default

All models contain an EEPROM (Electrically Erasable Programmable Read Only Memory) to store setup information. The switches necessary nonvolatile which means that the information removed. case.

The EEPROM provides tremendous system flexibility since all of the module's setup parameters may be configured remotely through the communications port without having to physically change switch settings. There is one minor drawback in using €EPROM instead of switches; there information in the module. It is impossible the baud rate, address, parity and other settings are. It is difficult to establish communications with a module whose address and baud rate are unknown. overcome this, each module has an input pin labeled DEFAULT. By connecting this pin to Ground, the module

Default Mode. The Default Mode setup is: Grounding the DEFAULT' pin does not change any of the setups stored in

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

A

module in Defautt Mode will respond illegal values (NULL, CR, command for proper responses. The ASCII vahe of the module address may be

Mode

to

specify baud rate, address, parity, etc. The memory is

No

batteries are used

300

EEPROM

so

it

is never necessary

is

to

tell

is

put in a known communications setup called

baud,

no

panty, any address is recognized.

replaces the

is

retained even if power

no visual indication of the setup

just

by looking at the module what

usual

to

open the module

(RS)

in

the module. In Default Mode, all commands

to

any address except the four identified

$,

#).

A dummy address must be included in every

array

of

is

To

command to

1-2

1700

USERS

MANUAL

read back with the

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 will with the Setup (SU)

command. Baud rate and parity setups may

Default values of the module automatically performs a program reset and configures itself to the baud rate and parity stored in the setup information.

The Default Mode terminal

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

modules.

RS-232

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

using a connections shown in the quick hook-up drawings, Figures

module in the Default Mode by grounding the Default' terminal. Initialize the terminal communications package on

mode. Since this step vanes

manual

Begin by typing

respond with an you have a response from the module you can turn to the Chapter familiar with the command

or

computer for the purpose of identifying and modifying setup values. In

8

not

dumb

for

instructions.

RS

command. An easy way

'?

prompt.

300

baud and no parity. When the DEFAULT* pin is released,

is

intended to be used with a single module connected

RS-485

required to begin using your

terminal

Quick

or

$1DI

and pressing the Enter

*

followed by the data reading at the input, typically

Hook-Up

a

computer that acts like a dumb terminal. Make the

your

from

computer to computer, refer

set.

to

determine the address character

be

changed without affecting the

M1700

computer

module. We recommend that

to

or

Return key. The module will

1.1

or

put

it

into the "trminal"

to

your computer

Start

1.2.

8000.

4

and get

to

a

by

Put the

Once

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

address delay. Refer

of

1,

300

baud fate, no linefeeds, no parity, no echo and two-character

to

the Chapter 5 to configure the module to

+

10

to

+30

Ydc

Power

Supply

-0

+Q

1

b

A

-

@

&,

8 8

Q

@

8

3

your

BB2

301

800'EY

DEFAULT*

TRRNSMIT

RECEIYE

I+vs

I

application.

M1711

DiGITRL

L'O

R.--pZC

9005

607

608

609

BBR

B0B

Figure

1.1

RS-232

Quick Hook-Up.

Introduction

*

B04

BE

B03

1802

BBC

BBD

1-3

Figure

RS-485

An evaluation purposes. This connection should never be used for a permanent installation. Figure up.

limited to

All

requirement. With this connection, characters generated echoed back. be turned off.

If

to

1.2

RS-485

Quick

RS-485

This

connection

less

terminals that

the current limiting capability

lkC2

resistor in series with the

Quick Hook-Up.

Hook-up

module may be easily interfaced

will

than

50mA

use

To

avoid double characters,

to

work provided the

and the

1488 and 1489 style interface

a

RS-232

RS-232C

of

the

RS-232

port

to

an

RS-232C

is

only suitable for benchtop operation and

RS-232C

receive threshold is greater than

the

RS-232C

output.

local echo

output is uncertain, insert a

transmit output

terminal for

1.3

shows

IC’s

by

the terminal will be

on

the terminal should

will

satisfy this

the hook-

is

current

OV.

1

OOR

1-4

1700

USERS

MANUAL

Figure

1.3

SlOOO

Software

S1000

software

RS-485

Software

is

available

tuns

Quick

Hook-Up

to

assist the user

on

the

IBM

compatible

with

an

RS-232

in

setting

Pc's

up

and

Port.

the

1700

is

available free

modules. The

of

charge.

Chapter

2

Functional Description

The Keithley MetraByte monitoring of on-off signals in response to simple commands from computer. Digital commands are transmitted to the

RS-232

form of simple English ASCII character strings for ease of use. The ASCH protocol allows the units intelligent controllers and computers.

or

RS-485

to

MI700

communications links. Commands and responses are in the

be interfaced with dumb terminals and modems as well as

Digital

I/O

modules provide remote control and

Mi700

units using standard

a

host

-

DATA

DATA*

RS-485

INTERFACE

EEPROM

TRANSMIT

\

RECE~YE

\

-

MICRO-

PROCESSOR

OUTPUT

-

DRIVERS

H

t

EVENT

COUNTER

F

(10

TO

30V)

Figure Figure

microprocessor is used the bi-directional the host computer through a serial communications communications components are used

485

thoroughly checked for syntax and data errors. Valid commands are then processed available to configure and control the digital commands are then produced

host over the An Electrically Erasable Programmable Read-Only Memory (EEPROM) is used to

retain important data even contains setup information such

I/O configuration data.

2.1

Digital

I/O

Functional Block Diagram.

2.1

shows a functional block diagram

to

provide

I/O

lines. The microprocessor receives commands and data from

communications standard. Commands received

to

complete the desired function. A wide variety

by

RS-485

serial

link.

if

Y+

>-I

GND

I

an

intelligent interface between the host and

to

interface the microprocessor

I/O

the microprocessor and transmitted back to the

the module is powered down. The EEPROM

as

the address, baud rate, and parity as well as

POWER

of

a

M1712.

by

the microprocessor are

lines. Responses

An &bit

port.

of

commands are

I

CMOS

Specialized

to

the

RS-

to

the host

2-2

1700

Each digital line on the

by

the user to be an input or an output. The direction assignments of all the lines

are stored in

the

M1712

USERS

EEPROM

is powered up.

MANUAL

M1712

so

is bidirectional and may be individually configured

that the lines are automatically configured each time

+5Y

1

DDK

crp

INPUT

w

OUTPUT

Figure Figure

darlington circuit capable

30V.

package is resistors are not provided in the modules.

When the input state is read by the microprocessor through an input protection circuit consisting of a from 0 to driver off, the than

2.2

The maximum total current that may be handled by

+5V.

<

\

I

Digital

2.2

is

a detail diagram

IA.

110

pin is configured

1

30V

without damaging the microprocessor.

lOOK

v

I/O

Circuit.

of

sinking

a single

110

200mA

line circuit. The output driver

with a maximum output voltage

the

The output saturation voltage at

as

an input,

OOK

resistor and diodes. This allows the input values

200mA

the

output driver

is

Note

resistor produces a leakage current

if

the

I/O

BIT

GND

is

a

of

MI711

1.2V

is

that with the output

I/O

or

M1712

max. Pullup

turned

off.

The

to

range

line is greater

When a read function is read back even verify the state of the output.

is

performed on an

if

the pin is configured as

I10

pin, the actual logical state

an

output. this provides a means to

of

the pin

Functional Description

2-3

AC

-

BOO

B01

figure Figure

relays. When electromechanical relays are used, always include a flyback diode to avoid damage

2.3

Digital Outputs Used With Relays.

2.3

shows typical connections

to

the output driver.

8

1

N400

8

-

to

solid-state relays and electromechanical

-

+Ys

1

-

+5Ydc

PP

EVENT

COUNTER

1

OOpF

lOOK

+5VdC

PP

INPUT

Figure Figure

pins but it has the event counter circuitry added on. The event counter circuitry

consists filtering. The event data

event signal

2.4

Events Counter Circuit.

2.4

is a detail schematic

of

input protection components and a capacitor to provide some noise

is

to

the rnicroprosser.

,

\

of

the BOOlEV pin. This pin is identical to all other

buffered

by

a Schmitt-trigger gate which outputs

lOOK

the

BB0/EV

2-4

1700

The microprosser contains a user-programmable counter input. The filter is necessary when the event signal is derived from mechanicat contacts such selectable for setting

.

USERS

0,520

MANUAL

as

switches or relays. The filter constant is user-

or

50ms.

Figure

filter

to

2.5

shows the filter action

debounce the event

for

the 5ms

EYENT

SAMPLE

FILERED

Figure

The microprosser samples the event input

be high for at least five consecutive samples before it will be counted as a high transition. Similarly, the input must be low for five sample periods before it is counted as a low signal. consecutive samples, etc.

The last converts the

in the module.

EEPROM.

RS-232

COUNTER

CLOCK

SIGNAL

2.5

Event Counter Debounce Filter.

major

raw

On

communications standard.

H

block

10

to

It

produces

RS-232

If

the filter

in the diagram is the power supply. The power supply

30

volts supplied by the user into regulated voltages used

+5V

units, the power supply produces

at

is

set for

necessary

lrns

intervak. The input signal

20ms,

the input must be stable for

to

operate the microprocessor and

fl

OV

necessary for the

must

20

Chapter

3

Communications

Introduction

The M1700 modules have been carefully designed to be easy to interface to all popular computers and terminals. All communications are performed with printable ASCII characters. This allows the information to be processed with string functions common to most high-level languages such as BASIC. For computers that support RS-232C, no special machine language software drivers are necessary for operation. The modules can be connected to auto-answer modems for long-distance operation without the need for supervisory computer. The ASCII format makes system debugging easy with a dumb terminal.

The Keithley MetraByte system allows multiple modules to be connected to a

a

communications port with strung together on one cable; units is about ten, although a string of 124 units is possible. The modules communicate with the host on a polling system; that is, each module responds to its own unique address and must be interrogated by the host. never initiate a communications sequence. protocol must be strictly observed errors.

single 4-wire cable. Up to

124

with repeaters. A practical limit for RS-232C

to

avoid communications collisions and data

to

and from the modules

32

RS-485

A

simple command/response

modules may be

A

module can

a

Communication ASClf command codes such as all commands

would

look like this:

Command:

Response:

A commandlresponse sequence is not complete until a valid response is received. The host may not initiate a new command until the response from previous command is complete. Failure to observe communications collisions. A valid response can be in one of three

1) a normal response indicated by a ' prompt

2)

3)

When a module receives a valid command, it must interpret the command, perform the desired function, and then communicate the response back to the host. Each command has an associated delay time calculating the response. appropriate amount error has occurred. After the communications time-out response data

to

the M1700 modules is performed with two- or three- character

DO

for Digitai Output. A complete description of

is

given in the Chapter

$1

RD

*+99999.99

an error message indicated by a a communications time-out error

If

the host does not receive a response in an

of

time specified in Table

is

forthcoming. This error usually results when an improper

4.

A

typical commandlresponse sequence

this

' ? '

prompt

in

which the module is busy

3.1,

a communications time-out

it

a

rule will result in

forms:

is assumed that no

3-2

1700

USERS

MANUAL

command prompt specification for each command:

Mnemonic

ACK,

CB,

CE, CP, DI,

RD,RP,

EC,

AOP,

W, Table The timeout specification is the turn-around time from

to

RS-232

RS-232C

transfer between computing equipment.

will

Although the equipment to a computer, the Keithley MetraByte system allows modules to be connected in a daisy-chain network structure.The advantages offered by the

However,

RS,

RE,

RW,

CIA,

CMC, CMD,

CT,

SU,

3.1

Response Timeout Specifications.

when the module starts to transmit a response.

C

is the most widely used communications standard for information

interface

1)

widely used by all computing equipment

2)

no additional interface hardware in most cases

3)

separate transmit and receive lines ease debugging

4)

compatible with dumb terminals

RS-232C

1)

low noise immunity

2)

short usable distance

3)

maximum baud rate

4)

greater communications delay in multiple-module systems

5)

less reliable-loss

6)

wiring is slightly more complex than

7)

host software must handle echo characters

or

address is transmitted. The table below lists the timeout

Timeout

I

5.0

DO,

RA, RAB,

RSU,

SB,

SP,

RIA,

RID,

RIV,

RCT,

CME,

CMT

AIO,

ID,

IV

to

virtualIy all popular computers without any additional hardware.

RS-232C

standard

RAP,

RB,

RCM,

RR,

WE

AtB, AIP, AOB,

RS-232C

is

designed

the

receipt

versions of the

to

connect a single piece

ms

115.0

I

100

of

a

1700

ms

command

for

RS-232C

standard are:

suffers from severaI disadvantages:

-

50

to

200

feet

-

19200

of

one module breaks chain

RS-485

Series

of

several

Single

Figure

the Default Mode to enter €he desired address, baud rate, and other setups (see

Setups). The use

communications line.

Multi-party

RS-232C

modules can be daisy-chained communications port. The wiring necessary to create the daisy-chain is shown in Figure Receive input of the next module in the daisy chain. This wiring sequence must be followed until the output input and must echo all received data (see Setups). Each module must be setup with its own unique address to avoid communications collisions (see Setups). In this network, any characters transmitted by the

the chain and passed on to the next station until

to the Receive input of the host. In this manner all the commands given by the

Module

1.3

shows the connections necessary to attach one module

Connectlon

of

echo is not necessary when using a single module on the

Connection

is not designed

3.1.

Notice that starting with the host, each Transmit output

of

the host.

All

to

be used in a multi-party system; however the MI

to

allow many modules

of

the last module in the chain is wired to the Receive

modules in the chain must be setup to the same baud rate

host

to

are received by each module in

the

information

to

a host. Use

700

be connected to a single

is

wired to the

is

echoed back

Communications

3-3

host are examined by every module. addressed and receives response any other modules in the chain until it reaches its final destination, the Receive input

on

of

the host.

the daisy chain network. The response data will be rippIe through

Figure

a

valid command, it will respond by transmitting the

3.1.

RS-232

If a module in the chain is correctly

Daisy

Chain

Network

The daisy chain network must be carefully implemented

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 to create a working chain:

1.

All

wiring connections must be secure; any break in the wiring,

power, ground or communications will break the chain.

2.

All

modules must be plugged into their connectors.

3.

All

modules must be setup for the same baud rate.

4.

All

modules must be setup for echo.

Software Considerations

If

the host device is a computer, it must be able

messages on its Receive input along with the responses from the module. This

can be handled by software string functions by observing that a module response

always begins with

A

properly addressed

characters in the command including the terminating carriage return. Upon

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 be stored in the module's internal receive

buffer. This character will be echoed after the response string is transmitted by the module. This situation will occur character on the command carriage return. In this case the linefeed character wilt

be

echoed after the response string has been transmitted.

a

' * '

or

'

'?

'

character and

M1700

to

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

module in a daisy chain will echo

if

the host computer appends a linefeed

to

handle the echoed command

ends

with a carnage return.

to

avoid the pitfalls

if

a character

all

of

is

received

the

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

in the chain receives a character it through the module's internal WART. This method is used to provide more

is

echoed

by

re-transmitting the character

3-4

1700

reliable communications since the UART eliminates any slewing errors caused by the transmission lines. However, this method creates a delay in propagating the character through the chain. The delay

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

USERS MANUAL

is

equal

to

the time necessary

to

Baud Rate

300

600

1200

240

0

4800

9600

19200

38400

One delay time is accumulated for each module in the chain. For example, if

modules are used in a chain operating at 1200 baud, the accumulated de[ay time

is

4

X

8.33

mS

=

33.3 mS This time must be added to the times listed in Table 3.1

to calculate the correct communications time-out error.

For

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

results in a delay of setup data, this sequence is repeated. Programmed communications delay is seldom necessary in an

adds one character of communications delay.

Changing

It is possible to change the baud rate process must be done carefully to avoid breaking the communications link.

in

the setup data (see Chapter

(00)

followed by an idle line condition for one character time. This

two

character periods. For longer deIay times specified in the

Baud Rate

Delay

33.30mS

16.70mS

8.33111s

4.17mS

2.08mS

1.04mS

RS-232C

520pS

260pS

four

5)

is implemented by sending a

daisy chain since each module in the chain

of

an RS-232C daisy chain on-line. This

NULL

1.

Use the Setup module in the chain. Be careful not to generate a reset during this process. reset can be caused by the Remote Reset

2. Verify that all the modules in the chain contain the new baud rate setup

using the Read Setup

for

the same baud rate.

3.

Remove power from all the modules for at least

to

power

loads in the new baud rate.

the new baud rate.

Using

A

dumb terminal can be used to communicate to a daisy-chained system. The terminal is connected in the same manner as a computer used as commands typed into the dumb terminal will be echoed by the daisy chain. avoid double characters when typing commands, set the terminal to full duplex

mode or turn off the loca[ echo. The daisy chain will provide the input command

echo.

RS-485

RS-485 is a recently developed communications standard multidropped systems that can communicate at high data rafes over long distances.

wires switching from

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

4.

Change the host baud rate

5.

Be sure

A

to

Daisy-Chain With

RS-485

(SU)

command to change the baud rate setup on each

A

(RR)

command

(RS)

command. Every module in the chain must be setup

to

the new value and check communications.

compensate for a different communications delay as a result of

A

is similar

0

to

5V

Dumb

to

RS-422 in that it uses a balanced differential pair of

to

communicate data. RS-485 receivers can handle

Terminal

or

power interruptions.

10

seconds. Restore

a

host. Any

to

satisfy the need

To

for

Communications

3-5

common mode voltages from -7V for transmission over great distances. balanced pair of wires for both transmitting and receiving. Since an system cannot transmit and receive at the same time system.

RS-485

support for this new standard. Interface boards are available for the compatibles and other gains popularity. An

Keithley MetraByte offers interface converters to convert These converters also include power supplies to power up to MetraByte modules. are available from Keithley MetraByte to string up to communications port.

RS-485

1)

2)

3)

4)

5)

6)

7)

8)

does have disadvantages. Very few computers

offers many advantages over

balanced line gives excellent noise immunity

can communicate with Keithley MetraByte modules at

communications distances up to

true multidrop; modules are connected in parallel

individual modules may be disconnected without affecting

other modules

up to

32

modules on one line; no communications delay due to multiple modules simplified wiring using standard telephone cable

RS-485

To

expand an

to

+12V

without

RS-485

124

equipment will become available as the standard

system usually requires an interface.

RS-485

loss

of

data, making them ideal

differs from

RS-232C:

10,000

feet.

with repeaters

system even further, repeater boxes

RS-422

it

is

inherently a halfduplex

or

terminals have built-in

RS-232C

124

by using one

38400

IBM

to

32

modules

RS-485

baud

PC

RS-485.

Keithley

on

one

and

RS-485

Figure Notice that every module has

of

modules may be unplugged without affecting the remaining modules. Each module must be setup with a unique address and the addresses can be in any order. All Setup). Also note that the connector pins notations telephone cable:

This

cable guarantee correct installation.

DATA* on the label is the complement

To

arranged

of

the transmission line should be avoided. For wire total, each end of the line should be terminated with a between DATA and DATA*.

Multidrop System

3.2

illustrates the wiring required for multiple-module

a

direct connection to the host system. Any number

RS-485

(B),

!Ax!

(B)

GND

(R)

v+

(v)

DATA Yellow

color convention is used

is

used,

minimize unwanted reflections on the transmission line, the bus should be

as

modules must be setup for no echo

(R),

(G), and

(Y).

This designates the colors used on standard 4-wire

on

to

avoid bus conflicts (see

each module are labelled with

LUcx

Black

Red

Green (G) DATA*

to

simplify installation.

it

is only necessary

a line going from one module to the next. 'Tree' or random structures

to

match the labeled pins with the wire color to

of

DATA (negative true).

If

standard 4-wire telephone

runs

220Q

RS-485

greater than

resistor connected

system.

500

feet

When using time when all stations on the line are in receive mode. During this time, the communications lines are left floating and are very susceptible

a

bi-directional

RS-485

system, there are unavoidable periods of

to

noise. To

Tektronix M1700 Series of Digital I/O to Computer Interfaces Users Guide

Specifications and Main Features

Frequently Asked Questions

User Manual

Contents

Introduction

RS-232C

RS-485