Digital Logic · Unit 5
Decoders and Encoders
Exam-focused notes for Decoders and Encoders (Digital Logic, BIT103): what the TU syllabus asks and how it has actually been tested, with 8 solved past questions from this unit.
What this unit covers
- Decoder design and operation
- BCD to decimal decoder
- BCD to seven-segment decoder
- BCD to excess-3 code converter
- Encoder circuits
BCD to excess-3 code converter
Define BCD code. Design BCD to Excess-3 Code converter with truth table and logic diagram.[10]
BCD (Binary Coded Decimal) is a binary encoding of decimal digits where each decimal digit (0-9) is represented by its 4-bit binary equivalent. Only 10 out of 16 possible 4-bit combinations (0000 to 1001) are valid; the remaining six (1010 to 1111) are inva...
Full solved answer →Design a combinational circuit that generates 9’s complement of a BCD number.[10]
- Input: a single BCD digit, 4 bits $B3 B2 B1 B0$, valid range decimal 0 to 9. - Output: 4 bits $X3 X2 X1 X0$ representing $9 - N$. - Inputs 10 to 15 are invalid BCD → treated as don't cares (X). Dec $B3B2B1B0$ $9-N$ $X3X2X1X0$ -----------------------------...
Full solved answer →BCD to seven-segment decoder
Design a BCD-to Seven-segment decoder to display decimal numbers 1, 2 and 4.[10]
A BCD (Binary Coded Decimal) to Seven-Segment Decoder takes a 4-bit BCD input and drives the seven segments (a, b, c, d, e, f, g) of a display to show the corresponding decimal digit. --- Segment Position ------------------- a Top horizontal b Top-right ver...
Full solved answer →Decoder design and operation
Implement the following function: F = Σ\SigmaΣ(0,1,3,4,5,8,9,10,15) using i) Decoder ii) Multiplexer iii) PLA[5]
- Function: $F(A,B,C,D) = \Sigma m(0,1,3,4,5,8,9,10,15)$ - 4 variables: A (MSB), B, C, D (LSB) - Minterms where F = 1: {0, 1, 3, 4, 5, 8, 9, 10, 15} - Minterms where F = 0: {2, 6, 7, 11, 12, 13, 14} m A B C D F ------------------ 0 0 0 0 0 1 1 0 0 0 1 1 2 0...
Full solved answer →Explain the concept of decoder with an example. [5]
A decoder is a combinational logic circuit that converts binary coded input into a set of outputs, where exactly one output is active (HIGH) for each unique combination of inputs. - It has n input lines and 2^n output lines - It "decodes" a binary code by a...
Full solved answer →Design of Full Adder Circuit Using 3-to-8 Decoder
A Full Adder is a combinational circuit that adds three input bits (A, B, Cin) and produces two outputs: Sum (S) and Carry (Cout). It can be implemented using a 3-to-8 decoder and OR gates.
A Full Adder is a combinational circuit that accepts three input bits (A, B, Cin) and produces two outputs: Sum (S) and Carry (Cout). Any combinational logic function can be implemented using a decoder and OR gates, because a decoder generates all minterms ...
Full solved answer →Design a decoder with three input lines but with only six output lines. If the value of the input corresponds to 6 or 7, then all output line should be asserted to signal an error. [5]
Design a decoder with: - 3 input lines: A₂, A₁, A₀ - 6 output lines: D₀ through D₅ - Error condition: If input = 6 (110) or input = 7 (111), ALL output lines are asserted (set to 1) --- A₂ A₁ A₀ D₀ D₁ D₂ D₃ D₄ D₅ Condition ----------------------------------...
Full solved answer →BCD to decimal decoder
What is Decoder? Design BCD to Decimal Decoder with Truth Table and Logic Diagram [10]
A decoder is a combinational logic circuit that converts an n-bit binary input code into a maximum of 2ⁿ unique output lines, where only one output is active (HIGH) at a time for each valid input combination. - It is essentially a minterm generator - For n ...
Full solved answer →Make Unit 5 stick
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