Msi Logic Circuit

MSI Logic Circuits
Wen-Hung Liao, Ph.D.

5/23/2001
Objectives
l Analyze and use decoders and encoders in various
types of circuit applications.
l Compare the advantages and disadvantages of LEDs
and LCDs.
l Utilize the observation/analysis technique for
troubleshooting digital circuits.
l Understand the operation of multiplexers and
demultiplexers by analyzing several circuit applications.
l Compare two binary numbers by using the magnitude
comparator circuit.
Objectives (contd)
l Understand the function and operation of code

converters.
l Cite the precautions that must be considered
when connecting digital circuits using the data
bus concept.
l Use CUPL's truth table entry format to
implement the equivalent of MSI logic circuits.
Common Operations
l Decoding/encoding
l Multiplexing
l De-multiplexing
l Comparison
l Code conversion
l Data busing
Decoder
l A decoder is a logic circuit that accepts a set of

inputs that represents a binary number and
activates only the output that corresponds to
that input number. Only
A0 O0 one
output
A1 O1 is high
Decoder for
each
input
AN-1 OM-1code.
Decoders(contd)
l Some decoders do not utilize all of the 2^N possible

input codes, e.g., BCD-to-decimal decoder has a 4-bit
input code and 10 output lines.
l Figure 9-2: 3-line-to-8-line decoder, or binary-to-octal
converter.
l ENABLE inputs (Figure 9-3), 74LS138.
l Combine four 74LS138s to function as a 1-of-32
decoder (Figure 9-4).
l 7442 BCD-to-decimal decoder (Figure 9-5).
BCD-to-7-Segment Decoder
l Take a 4-bit BCD input and provide the outputs

that will pass current thru the appropriate
segments to display the decimal digit.
l Figure 9-7 and 9-8 (TTL 7446, 7447).
LED vs. LCD Displays
l A Light-Emitting-Diode (LED) display

generates light energy as current is passed
thru the individual segments.
l A liquid-crystal display (LCD) controls the
reflection of available light (such as ambient
light or backlit.)
l LED is generally much brighter, LCD uses very
low power.
Encoders
l The opposite of the decoding process.

l An encoder has a number of input lines, only one of
which is activated at a given time.
l Octal-to-binary encoder (Figure 9-13).
l Priority encoder: ensures that when two or more inputs
are activated, the output code will correspond to the
highest numbered input. (Figure 9-14, 74147 decimal
to BCD priority encoder.)
Switch Encoder
l Figure 9-15, 74LS147.

l Switches corresponds to keyboards on a calculator
representing digits 0 through 9.
l Switches are normally open, so the encoder inputs are
normally HIGH and BCD output is 0000.
l When a digit key is pressed, the circuit will produce the
BCD code for that digit.
l Figure 9-16: circuit for keyboard entry of three-digit
number into storage registers.
Multiplexers (Data Selectors)
l A multiplexer (MUX) selects one of several

input signals and passes it on to the output.
l Routing of desired data input to the output is
controlled by SELECT inputs.
MUX
SELECT
Basic Multiplexers
l Two-input multiplexer: Z =I0S+I1S

l Four-input multiplexer
l Eight-input multiplexer: 74151 (Figure 9-23).
l 16-input multiplexer: Figure 9-24.
Multiplexer Applications
l Data routing
l Parallel-to-serial conversion (Figure 9-27).
l Operation sequencing (Figure 9-28).
l Logic function generation (Figure 9-29).
Demultiplexer (Data Distributors)
l A demultiplexer (DEMUX) takes a single input

and distributes it over several outputs.
l 1-line-to-8-line demultiplexer (Figure 9-31).
l Clock demultiplexer
l Security monitoring system (Figure 9-34).
l Synchronous data transmission system
l The receiver.
Magnitude Comparator
l Figure 9-40: 74HC85.

l Cascading inputs (Figure 9-41).
l Applications: digital thermostat.
Code Converter
l A code converter is a logic circuit that changes

data represented in one type of binary code to
another type of binary code.
l BCD-to-7-segment code converter.
l BCD-to-binary converter.
Data Bus Operation
l Register-to-register data transfer (Figure 9-49).

l Bus signals
l Simplified bus timing diagram
l Expanding the bus
l Bidirectional Busing

Msi Logic Circuit

Uploaded by

Copyright:

Available Formats

Msi Logic Circuit

Uploaded by

Document Information

Original Description:

Copyright

Available Formats

Share this document

Share or Embed Document

Sharing Options

Did you find this document useful?

Is this content inappropriate?

Copyright:

Available Formats

Msi Logic Circuit

Uploaded by

Copyright:

Available Formats

MSI Logic Circuits

Wen-Hung Liao, Ph.D.

l Understand the function and operation of code

l A decoder is a logic circuit that accepts a set of

l Some decoders do not utilize all of the 2^N possible

l Take a 4-bit BCD input and provide the outputs

l A Light-Emitting-Diode (LED) display

l The opposite of the decoding process.

l Figure 9-15, 74LS147.

l A multiplexer (MUX) selects one of several

l Two-input multiplexer: Z =I0S+I1S

l A demultiplexer (DEMUX) takes a single input

l Figure 9-40: 74HC85.

l A code converter is a logic circuit that changes

l Register-to-register data transfer (Figure 9-49).

You might also like