Encoders and Code converters
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Questions and Answers

In a priority encoder, what happens when multiple inputs are active simultaneously?

  • The encoder outputs the code corresponding to the highest priority input. (correct)
  • The encoder averages the input values to produce a combined output.
  • The encoder outputs the code corresponding to the lowest priority input.
  • The encoder outputs a special error code to indicate the conflict.

Which of the following is the primary function of a decoder?

  • To amplify a weak signal from an input source.
  • To convert a binary code into a single active output line. (correct)
  • To encode multiple inputs into a smaller set of outputs.
  • To compress data for efficient storage.

What is the primary difference between a decoder and an encoder?

  • A decoder increases the voltage of a signal, while an encoder decreases it.
  • A decoder is used for analog signals, while an encoder is used for digital signals.
  • A decoder is a sequential circuit, while an encoder is a combinational circuit.
  • A decoder converts from a coded format to a single output, while an encoder does the opposite. (correct)

How many output lines would a 3:8 decoder have?

<p>8 (A)</p> Signup and view all the answers

Which of the following logic gates is essential when constructing Boolean expressions using decoders?

<p>OR gate (C)</p> Signup and view all the answers

What would be the output if the inputs to a 3:8 decoder are A=1, B=0, and C=1?

<p>Output 5 is active. (A)</p> Signup and view all the answers

Which of the following is a practical application of decoders?

<p>Memory address decoding. (A)</p> Signup and view all the answers

For a 2:4 decoder, if the inputs are A=0 and B=1, which output will be active?

<p>Output 1 (B)</p> Signup and view all the answers

Consider a scenario where you need to activate one of eight different devices based on a 3-bit control signal. Which digital component is best suited for this task?

<p>3:8 Decoder (C)</p> Signup and view all the answers

What type of logic gate would you use to combine the outputs of a 3:8 decoder to generate the Boolean expression $F = A'BC + AB'C + ABC'$?

<p>OR gate (C)</p> Signup and view all the answers

What is the primary function of a code converter in digital systems?

<p>To translate data from one binary code to another. (C)</p> Signup and view all the answers

In a calculator, what is the role of the encoder situated between the keyboard and the CPU?

<p>To convert the decimal input from the keyboard into a binary code. (A)</p> Signup and view all the answers

Why are encoders used in keyboard applications?

<p>To represent each key press with a unique binary code. (B)</p> Signup and view all the answers

If a decimal input '7' is activated in a 10:4 encoder, what would be the BCD output?

<p>0111 (C)</p> Signup and view all the answers

What distinguishes a simple encoder from a priority encoder?

<p>A priority encoder provides an output based on the highest priority input when multiple inputs are active, while a simple encoder does not. (D)</p> Signup and view all the answers

What is the key difference between an encoder and a decoder?

<p>An encoder converts a single active input into a binary code, while a decoder converts a binary code into a single active output. (D)</p> Signup and view all the answers

A 4:2 encoder has four inputs and two outputs. If input 2 is active, which of the following binary codes would most likely be the output, assuming the inputs are numbered 0 to 3?

<p>10 (B)</p> Signup and view all the answers

Consider a system where a decoder's outputs are connected to an OR gate. What is the primary purpose of this configuration?

<p>To implement specific Boolean functions based on the decoder's outputs. (A)</p> Signup and view all the answers

In the context of code converters, what does '10:4 encoder' typically signify?

<p>The encoder has 10 input lines and 4 output lines. (B)</p> Signup and view all the answers

If a digital system requires converting data from one coding scheme to another without altering the information's actual value, which type of circuit is most suitable?

<p>Code Converter (B)</p> Signup and view all the answers

In a simple 8:3 encoder, what would be the output (A, B, C) if input 6 is active and all other inputs are inactive?

<p>1, 1, 0 (C)</p> Signup and view all the answers

Which Boolean expression accurately represents the output 'B' of an 8:3 encoder, based on the provided content?

<p>B = 2 + 3 + 6 + 7 (A)</p> Signup and view all the answers

What is the primary difference between a simple encoder and a priority encoder?

<p>A priority encoder includes additional logic to handle multiple active inputs, while a simple encoder may produce incorrect output. (B)</p> Signup and view all the answers

In a 10:4 priority encoder, if inputs 2 and 5 are active simultaneously, which input's code will the output represent?

<p>Input 5 (B)</p> Signup and view all the answers

According to the truth table for the 10:4 priority encoder, what is the output (ABCD) when input 2 is active and all inputs higher than 2 are inactive, regardless of the state of inputs 0 and 1?

<p>0010 (C)</p> Signup and view all the answers

Referring to the 4:2 priority encoder, if input 3 is active, what does this imply about the other inputs based on the priority encoding logic?

<p>The states of inputs 0, 1, and 2 are irrelevant. (C)</p> Signup and view all the answers

In the context of designing a 4:2 priority encoder, what method is suggested for simplifying the expressions derived from the truth table?

<p>Karnaugh Map (D)</p> Signup and view all the answers

A 4:2 priority encoder has inputs 0, 1, 2, and 3, with 3 having the highest priority and 0 the lowest. If inputs 1 and 3 are simultaneously active, which input will determine the encoder's output?

<p>Input 3, because it has the highest priority (C)</p> Signup and view all the answers

What is the primary advantage of using a priority encoder over a standard encoder in applications where multiple inputs may be active simultaneously?

<p>Guaranteed valid output corresponding to the highest priority input (D)</p> Signup and view all the answers

Consider a scenario where a system requires encoding multiple interrupt requests, and it's crucial to process the most important request first. Which type of encoder would be most suitable for this application?

<p>A priority encoder (D)</p> Signup and view all the answers

Flashcards

Code Converter

A combinational circuit that translates data from one binary code to another without changing its value.

Code Conversion Circuits

Circuits that perform code conversion.

Encoder (in Calculator)

Transforms a decimal number (keyboard input) into a binary code (like BCD) for the CPU.

Decoder (in Calculator)

Translates the binary code from the CPU to a seven-segment display.

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Encoder

A combinational circuit that converts one active input signal into a unique binary code.

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Encoder - Single Input

Encoders convert only one input at a time into a binary code.

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Encoder Specification

Denotes the number of inputs to outputs in an encoder.

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Decimal-to-BCD Encoder

Translates a decimal input to its BCD equivalent.

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10:4 Encoder Example

In a 10:4 encoder, activating decimal input 4 results in a BCD output of 0100.

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4:2 Encoder

An encoder with four inputs and two outputs, where only one input is active at a time.

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Priority Encoder

A digital circuit that outputs a binary code representing the most significant active input.

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Encoder Truth Table

A table that maps each input combination to its corresponding output in an encoder.

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Encoder Boolean Expressions

A=4+5+6+7, B=2+3+6+7, C=1+3+5+7 (for an 8:3 encoder).

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Encoder Logic Circuit

A diagram showing the arrangement of logic gates that implement the encoder's function.

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Priority Encoder Logic

If multiple inputs are active, the output corresponds to the highest numbered input.

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10:4 Priority Encoder

An encoder that converts 10 inputs into a 4-bit BCD code, giving priority to higher inputs.

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Simplified Expressions

Output expressions often can be simplified via boolean algebra or Karnaugh maps

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Karnaugh Map

A visual tool for simplifying Boolean expressions.

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4:2 Priority Encoder

An encoder that converts 4 inputs into a 2-bit code, prioritizing higher inputs.

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4:2 Priority Encoder Truth Table

A table showing all possible input combinations and their corresponding outputs, reflecting the priority logic.

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2:4 Decoder

A decoder with 2 inputs and 4 outputs. Each input combination activates a unique output.

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3:8 Decoder

A decoder with 3 inputs and 8 outputs. Each unique input combination activates a single, unique output.

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Decoder Applications

Using a decoder along with OR gates to implement complex Boolean functions.

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Truth Table

A table listing all possible input combinations and their corresponding outputs for a digital circuit.

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Boolean Expression

A symbolic representation of a logic function using Boolean variables and operators.

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Logic Circuit

A graphical representation of a digital circuit using logic gates to implement Boolean expressions.

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Decoder Function

A decoder converts n inputs into 2^n unique outputs

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Boolean Expression Simplification

The process of reducing the complexity of a Boolean expression while preserving its logical equivalence.

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Study Notes

  • A code converter is a combinational circuit which translates data without changing its value.
  • These converters are useful for compatibility between coding schemes or devices.
  • Code conversion is performed with encoders, decoders, and code converter circuits.
  • Required to operate electronic displays for calculators and clocks.

Code Converter

  • The input device for a calculator is a keyboard.
  • An encoder translates the decimal number pressed on the keyboard into a binary such as BCD code.
  • The CPU performs the operations in binary code.
  • The binary code translates from the CPU to a seven-segment display, by a decoder.

Encoders

  • Used where activation of a single key must produce a unique binary code.
  • Encoders have several inputs, and convert only one input at a time into a binary code.
  • Encoders are specified by the number of inputs to outputs such as 4:2, 8:3 or 10:4 encoders.
  • In a calculator encoders translate a decimal input to a BCD number.
  • A block diagram for a decimal-to-BCD or 10:4 encoder has 10 inputs on the left and 4 outputs on the right.
  • An encoder has one active input and produces a unique output.
  • A 10:4 encoder truth table is shown.
  • If decimal input 4 is activated, the output in BCD is 0100.
  • The output expressions and the logic circuit includes logic gates to correspond to the specific outputs.
  • An example 4:2 encoder has a truth table and outputs A=2+3 and B=1+3

Priority Encoder

  • A simple 10:4 encoder can be problematic when more than one input is activated, producing an incorrect output.
  • Priority encoders include logic to ensure that when 2 or more inputs are activated, the output corresponds to the highest numbered input.
  • When inputs 3 and 5 are activated, the output code will be 0101 (5).
  • The output expressions are written in a truth table, with simplified expressions.
  • Example 2 is a 4:2 priority encoder design.

Decoders

  • The opposite of an encoder.
  • Translate from the BCD code to decimals.
  • BCD codes form the input on the left, and the output lines are on the right.
  • Only one output line will be activated at one time.
  • A BCD 0011 input would activate the 3 output.
  • A 4:10 decoder has outputs depending on the corresponding inputs in a truth table.
  • The circuits can be represented as the output expressions and logic circuit.
  • Logic gates may be needed to properly decode the signal.
  • A 2:4 decoder has 2 inputs and 4 outputs, and similarly requires logic gates.

Decoder Applications

  • A Boolean expression can be constructed using a decoder and logic gates, constructed using a 2:4 decoder and an OR gate.
  • A three variable Boolean expression can be constructed using a 3:8 decoder combined with an OR gate.

Display Decoder

  • A common output to display decimal numbers is the seven-segment display.
  • The seven-segments are labeled with standard letters from a to g.
  • If the segments a, b, c, d, and g are lit, a decimal 3 appears.
  • A truth table for a display decoder is shown.

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Related Documents

Code Converter Digital Logic Lesson - Textbook

Description

Explanation of code converters and encoders. Code converters are combinational circuits that translate data without changing its value, useful for compatibility between coding schemes. Encoders are used where activation of a single key must produce a unique binary code.

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