Transcript Digital - TCAPS Moodle

Digital
• Analog – Electrical information that has an
infinite number of positions or states
between a minimum and maximum value
• Digital – Electrical information that has
only two possible positions or states, that of
the minimum and maximum value
• Examples -
Digital
• Bit – the fundamental units of digital information.
Can either be logic low (0) or logic high (1)
• Byte – 8 bits – the most common way digital
information is measured, stored and exchanged.
Ex- 1001 1110
• Nibble – 4 bits – upper nibble or lower nibble
• Word – 2 Bytes (16 bits)
TTL Family of Digital Components
•
•
•
•
TTL –Transistor – Transistor Logic
+ 5 Volts (2.4 - 5) = logic high = 1
0 V (0.4 - GND) = logic low = 0
0.4 – 2.4 V = Error
Other Digital Terms
• Clock – An electronic signal the changes
from 10 1 0 continually and
measured in MHz “heartbeat”
• Used for timing and coordination of digital
circuits
Other Digital Terms
• ADC – Analog to digital Conversion
• DAC – Digital to analog Conversion
• Address – A physical location normally
express in binary where a byte(s) of
information are stored
• ROM – Read Only Memory
• RAM – Random Access Memory
Digital Number Systems
• Three basic number systems used in the
digital world
• 1) Binary (base2)
• 2) Decimal (base10)
• 3) Hexcode (base16)
• Octal (base8) – obsolete
• Examples -
ASCII Code
• ASCII – American Standard Code for
Information Interchange
• The most common method for translating
digital information into alpha numeric
• Each letter, number character, or special
command is represented by one byte of
information
• Example – Z = 0101 1010
Methods of Digital Transfer
• Serial – the transfer of digital information one bit
at a time (minimum of 2 conductors) sometimes
called a “bit spit”
• Serial Port – approximately 100 Kbps
• MODEM – Modulator / Demodulator – a device
that modulates digital information into an analog
signal then back to digital
• Serial communication (modem speed) is normally
measure in bps (bits/sec)
• Baud –an older measurement that was described in
symbols / sec and was dependent on the
modulation technique (obsolete)
Universal Serial Bus - USB
• Universal Serial Bus (USB) – high speed
serial transfer (four conductors usually used
however only two needed)
• USB 1.1 – 12 Mbps
• USB 2.x – 480 Mbps
• Fire Wire – 400 Mbps
bps Example
• At a rate of 14,400 bps how long would it
take to send a 5.2 MByte Picture?
• Ans 2888 sec (48 min)
• At a rate of 12 Mbps, how long would it
take to transfer a 5.2 MByte picture?
• Ans – 3.47 sec
Parallel
• Normally used for short distance transfer of
digital information (i.e. printer)
• Can send 8 bits at once
• Requires a minimum of 12 conductors (8
data + 4 control)
• 2.5 Mbps
• Becoming obsolete
Transition State Diagrams
• Draw a transition state diagram for the
serial transmission of the ASCII code
character Z – 0101 1010
7 Basic Logic Gates
• Integrated Circuits (IC’s) – a “computer
chip” – a very small package of resistors,
transistors and other electrical components
that will provide some function.
• 7 basic logic gates -