Category : Tutorials + Patches
Archive   : CLASS.ZIP
Filename : CHAPTER.01
Data Communications
Prepared By Phil Marcello
Data Comm Network BBS
Rochester. N.Y.14611
716-328-3844
Chapter 1.0 Intro
.1 Basic Circuit
.2 Bits & Bytes
.3 ASCII
Chapter 2.0 The Interface
.1 Parallel Interface
.2 Serial Interface
.3 Parity & More
.4 Bit Length
.5 Data Blocks
.6 Protocols
.7 The UART
Chapter 3.0 More on the Interface
.1 Control Signal
.2 DCE & DTE
.3 Sync & Async
Chapter 4.0 Electrical characteristics
Chapter 5.0 Modulation
.1 Phase Modulation Layman's Terms
.2 Phase Modulation The Tech side
.3 Introduction of Clocking
Chapter 6.0 Introduction to Telephone Lines
Chapter 7.0 The switched Communications Network
Welcome to the world of Data Communications. A world of fast moving
technical innovation. Even as this course is being presented, the
technology is leaping forward.
The material in this course is presented in such a way as to hopefully
be of value to people of differing backgrounds and levels of technical
expertise.
Just who is Phil Marcello ?? Nobody of great consequence. Just a hard
working Senior Field Engineer for General Data Comm (6 years) with
5 years prior service with Racal Milgo, both relative giants in
the communications industry.
My experience is mostly in the commercial area, high speed synchronous
communication. To list my weaknesses would fill your hard drive.
My reference material at the moment but subject to expansion include
Bell System Technical References
"Data Comm Using The Switched Telecommunications Network"
"Data Comm Using VoiceBand Private Line Channels"
Technical Aspects of Data Communications by John E. McNamara
The Modem Reference by Michael A. Banks
Technical Package For the Tellabs Registered Network Interface System
A General Data Comm publication
Warwick Networking Products Catalog
Chapter One - Some Basics
1.1 Basic Circuit
For those of you out there, who know how to type on a keyboard
and run a program but nothing else, the following basics are for
you.
The flashlight represents the most basic electrical circuit.
A battery - A switch - and a lightbulb.
When the switch is closed, electrons are allowed to flow and the
lightbulb lights. This is an "ON" condition.
When the switch is opened, the circuit path is broken. Electrons
can not flow, the lightbulb is "OFF"
With just this example, we have created a 2 state circuit; On and OFF.
Let the numeral 1 represent the on condition and 0 represent the off
condition and we now have a simple way of expressing what the circuit
is trying to tell us.
This circuit can be used to provide information to tell us something.
When the light is on "Do Not Enter The Room" is an example.
This is Information. Information is Data. Conveying information
is Data Communications.
Instead of a light bulb, we feed the "on" (1) or "off" (0) into
a logic circuit. This is the bassis for all computer operation.
Data becomes more valuable as more people have access to it. Data stored
at one location and available only to people at that location, limits
the potential value of that Data.
Providing access to that data by people all over the country is called
Data Communications.
The transfer of information inside a computer is usually handled via
a Parallel Bus. If one lightbulb circuit can provide us with 2 states
of information then 8 light bulbs operating side by side can give us
8 channels of Data simultaneously. Eight lights Bulbs flashing
1's and 0's conveying Coded information to any onlooker.
1.2 Bits & Bytes
One channel, One on/off circuit, provides us with one BIT of Data.
A "0" (zero) bit or a "1" (one) bit.
When we put bits of data together, we get a BYTE.
The term byte is interpreted differently by different people.
A BYTE is a predetermined number of BITS.
We can say that our BYTE will be equal to 8 BITS. Thus our 8
circuits provide us with one BYTE.
00101010 is 8 bits and equals one byte
Or we could say that our BYTE is equal to 4 Bits. Then we would
have to separate our 8 circiuts. We would then say circuits 1,2,3
and four make up one BYTE (of 4 bits) and circuits 5,6,7 and 8 make
up another BYTE of four bits. To get the same effect as one 8 bit
BYTE we would eventually have to put them together anyways. We do
this ; putting smaller BYTES together ; by creating a WORD.
0101 1011 are two, four bit bytes making a WORD
So we can either say we have a BYTE of 8 bits
OR we can say we have a WORD consisting of 2 BYTES at 4 bits per BYTE.
Since the terms are used differently by different authorities, I have
selected these terms for our purpose.
Back to our 8 circuits. Since these circuits provide us with data,
it is time we called them by their correct name. Each circuit
is a DATA CHANNEL. They are designated Data Channel or Channel
1, 2, 3 ... etc.
The information on these Channels are kept in Sync by a common
clock that allows the 8 data bits to enter the channel and leave
the channel at the same time. Where these channels connect to
inside the computer is better left to a computer course.
I also chave no desire at this point to go into Boolean Algebra
or Binary Arithmetic. Suffice to say, that just as the Morse Code
uses a combination of Dih's and Dah's to represent letters of the
alphabet, we use combinations of 1's and 0's to represent Alpha
characters (letters), Numerical Codes (numbers), Punctuation and
control characters.
1.3 ASCII Code
By combining the 8 characters in our Bus together we have 8 channels
of 2 states each giving us 256 possible combinations. HOW !!! Just
count all the different possible combinations that 8 channels of
1's and 0's can provide for us.
00000000 00000100
00000001 00000101
00000010 00000110 etc etc etc all the way
00000011 00000111 up to 11111111
On the next page is provided the means for using these 1's and 0's
as information, however to make ourt life easier, we will be using
WORD format, 2 BYTES at 4 bits per byte.
What is needed now is to turn those 1's and 0's into characters that
we can understand. Well someone did it for us and they created a
standard list called
American Standard Code for Information Interchange
more affectionately known as ASCII (pronounced ASSKEY)
ASCII TABLE 8 Bit (Octal is provided for those who need it)
Binary Alpha Octal Binary Alpha Octal
Code Numerics Code Code Numerics Code
0000 0000 NULL 000 1000 0101 E 105
0001 SOH 001 0110 F 106
0010 STX 002 0111 G 107
0011 ETX 003 1001 0000 H 110
0100 EOT 004 0001 I 111
0101 ENQ 005 0010 J 112
0110 ACK 006 0011 K 113
0111 BEL 007 0100 L 114
0001 0000 BS 10 0101 M 115
0001 HT 11 0110 N 116
0010 LF 12 0111 O 117
0011 VT 13 1010 0000 P 120
0100 FF 14 0001 Q 121
0101 CR 15 0010 R 122
0110 SO 16 0011 S 123
0111 SI 17 0100 T 124
0010 0000 DLE 20 0101 U 125
0001 DC1 21 0110 V 126
0010 DC2 22 0111 W 127
0011 DC3 23 1011 0000 X 130
0100 DC4 24 0001 Y 131
0101 NAK 25 0010 Z 132
0110 SYN 26 0011 [ 133
0111 ETB 27 0100 \ 134
0011 0000 CAN 30 0101 ] 135
0001 EM 31 0110 ^ 136
0010 SUB 32 0111 _ 137
0011 ESC 33 1100 0000 ` 140
0100 FS 34 0001 a 141
0101 GS 35 0010 b 142
0110 RS 36 001Bankrot 143
0111 US 37 0100 d 144
0100 0000 SP 40 0101 e 145
0001 ! 41 0110 f 146
0010 " 42 0111 g 147
0011 # 43 1101 0000 h 150
0100 $ 44 0001 i 151
0101 % 45 0010 j 152
0110 & 46 0011 k 153
0111 ' 47 0100 l 154
0101 0000 ( 50 0101 m 155
0001 ) 51 0110 n 156
0010 * 52 0111 o 157
0011 + 53 1110 0000 p 160
0100 , 54 0001 q 161
0101 - 55 0010 r 162
0110 . 56 0011 s 163
0111 / 57 0100 t 164
0110 0000 0 60 0101 u 165
0001 1 61 0110 v 166
0010 2 62 0111 w 167
0011 3 63 0000 x 170
0100 4 64 0001 y 171
0101 5 65 0010 z 172
0110 6 66 0011 { 173
0111 7 67 0100 | 174
0111 0000 8 70 0101 } 175
0001 9 71 0110 ~ 176
0010 : 72 0111 DEL 177
0011 ; 73
0100 < 74
0101 = 75
0110 > 76
0111 @ 77
1000 0000 A 100
0001 B 101
0010 C 102
0011 D 103
0100 E 104
Very nice! Thank you for this wonderful archive. I wonder why I found it only now. Long live the BBS file archives!
This is so awesome! 😀 I’d be cool if you could download an entire archive of this at once, though.
But one thing that puzzles me is the “mtswslnkmcjklsdlsbdmMICROSOFT” string. There is an article about it here. It is definitely worth a read: http://www.os2museum.com/wp/mtswslnk/