232BOB15299 Manual
Cover Page
B&B Electronics Mfg Co Inc 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax 815-433-5104
B&B Electronics Ltd Westlink Commercial Park Oranmore, Galway, Ireland Ph +353-91-792444 Fax +353-91-792445
RS-232 BreakOut Box
CE
CE
CE
CE
Model 232BOB1
Document No. 232BOB15299
This product Designed and Manufactured
of domestic and imported parts by
International Headquarters
B&B Electronics Mfg. Co. Inc.
707 Dayton Road -- P.O. Box 1040 -- Ottawa, IL 61350 USA
Phone (815) 433-5100 -- General Fax (815) 433-5105
Home Page: www.bb-elec.com
Sales e-mail:
sales@bb-elec.com
-- Fax (815) 433-5109
Technical Support e-mail:
support@bb.elec.com
-- Fax (815) 433-5104
European Headquarters
B&B Electronics Ltd.
Westlink Commercial Park, Oranmore, Co. Galway, Ireland
Phone +353 91 792444 -- Fax +353 91 792445
Home Page: www.bb-europe.com
Sales e-mail:
sales@bb-europe.com
Technical Support e-mail:
support@bb-europe.com
1993 B&B Electronics -- Revised January 2000
November 5299 B&B Electronics RESERVED. No part of this publication may be reproduced or transmitted
in any form or by any means, electronic or mechanical, including photography, recording, or any information
storage and retrieval system without written consent. Information in this manual is subject to change without
notice, and does not represent a commitment on the part of B&B Electronics.
B&B Electronics shall not be liable for incidental or consequential damages resulting from the furnishing,
performance, or use of this manual.
All brand names used in this manual are the registered trademarks of their respective owners. The use of
trademarks or other designations in this publication is for reference purposes only and does not constitute an
endorsement by the trademark holder.
232BOB15299 Manual
Table of Contents
i
B&B Electronics Mfg Co Inc 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax 815-433-5104
B&B Electronics Ltd Westlink Commercial Park Oranmore, Galway, Ireland Ph +353-91-792444 Fax +353-91-792445
Table of Contents
INTRODUCTION .......................................................................................1
BITS, BYTES, AND VOLTAGES..............................................................3
TALKING TO THE OUTSIDE WORLD ...................................................4
PLUG AND RECEPTACLES: The First Incompatability..........................6
PIN ASSIGNMENTS: The Second Incompatability ..................................7
THE DIFFERENCE BETWEEN CONTROL SIGNALS AND DATA
SIGNALS............................................................................................9
RS-232D PINS AND PIN ASSIGNMENTS .............................................10
THE IMPORTANCE OF SOFTWARE ....................................................13
HOW TO SUCCESSFULLY CONNECT TWO RS-232 DEVICES ........15
GENERAL CONSIDERATIONS..............................................................16
THE B&B BREAK-OUT BOX .................................................................18
AT THE INTERFACE...............................................................................20
DECLARATION OF CONFORMITY ....................................................A-1
232BOB15299 Manual
1
B&B Electronics Mfg Co Inc 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax 815-433-5104
B&B Electronics Ltd Westlink Commercial Park Oranmore, Galway, Ireland Ph +353-91-792444 Fax +353-91-792445
INTRODUCTION
The RS-232D Standard is the set of guidelines specifying how
two pieces of computer equipment should be cabled together so that
they can communicate in a certain way. The problem with this
standard is that it is not a "standard" at all. It isn't a standard in the
same sense that American television signals, LP records, and the
alternating current that flows from the typical wall socket are.
"Recommended Standard Number 232, Revision D", as defined and
promulgated by the Electronics Industry Association (EIA), is
something that simply is not scrupulously followed by manufacturers
of printers, computer terminals, graphic plotters, data acquisition
equipment, or any of the other gear that is sold as "RS-232D
compatible."
Most standards, like those cited above, are as crisp, clear, and
uncompromising as a snapshot. A unit is either compatible with the
standard or it is not, and if it's not, it doesn't work. Period. Record
and appliance manufacturers aren't fools. As a result, any LP
record can be played on any turntable, and everything from a radial
saw to a food processor will spring to life when plugged into an
electrical outlet anywhere in the country.
Why can't every dot matrix and letter-quality printer behave the
same way when plugged into any personnel computer? It is fair to
say that more hours have been wasted over the apparently simple
task of getting Computer A to talk to Printer B than over any other
problem in personal computing.
What all of this means is that whether you are a dealer, an end
user, a corporate information center, or anyone else, if you set out to
connect two "RS-232 compatible" devices you are, in fact,
embarking upon a veritable magical mystery tour of conflicting
interfaces and creative wiring. You must first figure out what each
device is doing with the 25 pins or sockets that compose the RS-232
interface. Then you must figure out how to build or specify a cable
that fiddles with those pins in a way that successfully mates the two
machines.
2
232BOB15299 Manual
B&B Electronics Mfg Co Inc 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax 815-433-5104
B&B Electronics Ltd Westlink Commercial Park Oranmore, Galway, Ireland Ph +353-91-792444 Fax +353-91-792445
The B&B Break-Out Box can be a big help in both phases of the
operation. If you're experienced at this sort of thing, you might want
to skip ahead to the step-by-step instructions presented later in this
manual. But if serial communications is new to you, stick around
and we'll see if we can't bring some order to the chaos of the RS-
232 "Standard" and give you the background information you need
to solve almost any machine mating puzzle.
232BOB15299 Manual
3
B&B Electronics Mfg Co Inc 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax 815-433-5104
B&B Electronics Ltd Westlink Commercial Park Oranmore, Galway, Ireland Ph +353-91-792444 Fax +353-91-792445
BITS, BYTES, AND VOLTAGES
The first thing you need to know is that computers communicate
in "bits", a term that is short for "binary digits." Just as a bicycle has
two wheels, a binary digit has two forms. Both of them are electrical,
of course, and can be variously described as ON or OFF, 1 or 0, HI
or LOW, SPACE or MARK, and so on. For our purposes, we'll think
of bits at the physical level, that is, as two different electrical
voltages, each of which exists on a wire or other conductor for a
certain number of microseconds.
If electricity is the lifeblood of a personal computer, bits are its
red and white corpuscles. They are constantly whizzing around
inside a system, even when it isn't doing anything in particular. But
unlike corpuscles, bits don't whiz at random. They are, for the
computer, a means of communication with its separate parts. When
the computer wants one of its disk drives to come on, for example, a
pattern of bits is dispatched to carry the message to the circuit board
that controls the disk drive, and instantly the drive is turned on.
Other bit patterns, fired off to other sections of the system, control
other operations.
The next thing that you need to know is that in virtually all micro
or personnel computers, eight bits are required to send any
message. All of the bits are required to send any message. All of
the bits in a given message depart and arrive at the same time. In
other words, bits travel in groupings of eight and they travel abreast.
To make it possible for bits to travel in this fashion, the internal
components of most computers are typically connected by electrical
highways. Think of the highways as wires and imagine them
running between any Point A and any Point B within the machine
and you'll begin to get the picture. Naturally, all of the highways or
"wires" are parallel. And that, if you haven't guessed it already, is
why this arrangement is called "parallel communications".
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