Decoders

Duration: 5 min

This video lesson is available to enrolled students.

Return to /learn/HPSC-PGT-COMPUTER-SCIENCE/digital-logic-circuits/combinational-circuit/demux-decoder-encoder/asset-decoders after enrolling

Inside: a video lesson and guided study material.

Module outline

  1. HPSC Interview Preparation: Interview Preparation
  2. Python Language: Introduction to Python, Tokens, Variables, Data Types, I/O, Operators & Expressions, Control Flow & Looping, Collections & Strings, Functions & Modules, File Handling & Data Analysis, DSA using Python
  3. Data Structure & Algorithms: Introduction to DS, Array, Stack, Queue, Linked List, Tree, Graphs, Hashing, Algorithm Analysis, Sorting Algorithms, Minimum Spanning Trees, Time Complexity Analysis, Graph Theory, Shortest Path Algos
  4. Computer Networks: Introduction to CN, Data Communication, DLL: Access Control, DLL: Flow Control, Data Link Layer - Ethernet, Net Layer: IPv4 & Proto, Net Layer: IP Addressing, Transport Layer Services, TL: Congestion & UDP, Application Layer, Hardware basics, Network Security
  5. Computer System & Organisation: Basics of COA, Cache Memory Organization, Input Output Organisation, Pipelining, Instr Formats & Modes, Control Unit Design, Programming the Basic Computer
  6. Database Management System: Basics of DBMS, ER Diagram, Relational Model & Functional Dependencies, Keys & Integrity Constraints, Normalization (1NF - BCNF), Decomposition Properties & 4NF, SQL, File Organization & Indexing, Transaction Management, Concurrency Control
  7. Operating Systems: Introduction to OS, Process Management, CPU Scheduling, Process Synchronization, Deadlock, Threads & Process Creation, Memory Management, Virtual Memory, Disc Scheduling
  8. Digital Logic & Circuits: Digital Systems & Boolean Basics, Logic Gates & Hardware, Boolean Expression, Boolean Minimization, Combinational Circuit, Sequential Circuits, Number System, Number Representation
  9. Theory Of Computation: Introduction to TOC, Deterministic FA (DFA), Non-Deterministic FA, Regular Expressions, Grammar, Regular Language Properties, Pushdown Automata & CFG, Turing Machines, Moore & Mealy Machines
  10. Compiler Design: Intro to Compilers, Lexical Analysis, Grammar & CFG, Syntax Analysis: Top-Down, Syntax Analysis: Bottom-Up, Semantic Analysis & SDT, Intermediate Code Gen, Code Optimization, Run Time Environment
  11. Software Engineering: Fundamentals of Software Engineering, Software Requirements and Quality Assurance, Software Design, Estimation and Metrics, Software Testing, Software Maintenance and Configuration Management, Data Warehousing & Mining
  12. Introduction to Emerging Trends: Emerging Tech Trends
  13. Digital Society & Cyber Law: Society, Law & Ethics
  14. HPSC PGT Previous Year Paper:
  15. HPSC Assistant Professor Previous Year Paper:
  16. Live Sessions: HPSC Live Sessions, EMRS TGT/PGT Live Class
  17. Full Mock Test:
  18. HPSC PGT - MOCK Test Series:
AI summary & chapters

AI Summary

An AI-generated summary of this video lecture.

This lecture demonstrates how to construct a 4-to-16-line decoder using two 3-to-8-line decoders with enable inputs. The instructor begins by drawing a block diagram for the target 4x16 decoder, labeling its four inputs as I0 (LSB) through I3 (MSB) and its sixteen outputs as D0 to D15. The solution involves using the three lower-order bits (I0, I1, I2) as common data inputs to both 3x8 decoder blocks. The most significant bit (I3) is used to control the enable inputs of each decoder: when I3=0, the upper decoder is enabled to produce outputs D0-D7; when I3=1, an inverter allows the lower decoder to be enabled to produce outputs D8-D15. This method effectively doubles the output capacity of a 3x8 decoder to create a 4x16 decoder.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The instructor introduces the problem of connecting two 3-to-8-line decoders to form a 4-to-16-line decoder. A block diagram for the target '4x16 Decoder' is drawn on the whiteboard, with inputs labeled I0 (LSB) to I3 (MSB) and outputs D0 to D15. The instructor then begins drawing the first 3x8 decoder block, labeling its inputs I0, I1, I2 and an enable input E.

  2. 2:00 – 5:00 02:00-05:00

    The instructor draws a second 3x8 decoder block in green ink, stacking it below the first. The inputs I0, I1, and I2 are connected to both decoders. The MSB (I3) is circled in red and wired to the enable inputs of both decoders. An inverter is added between I3 and the upper decoder's enable pin, while a direct connection is made to the lower decoder. The outputs are labeled D0-D7 for the upper block and D8-D15 for the lower block.

  3. 5:00 – 5:19 05:00-05:19

    The final diagram is completed, showing the logic conditions for each decoder. The instructor writes 'I3=0' and 'I3=1' to indicate the enable states. The outputs of both 3x8 decoders are connected to the final 4x16 decoder block, demonstrating how the MSB selects which half of the output range is active based on the enable logic.

The core concept taught is decoder expansion using enable inputs. By sharing the lower-order address lines (I0-I2) across multiple smaller decoders and using the higher-order bit (I3) to control their enable pins, a larger decoder can be synthesized. The use of an inverter on one enable line ensures that only one 3x8 decoder is active at any given time, preventing output conflicts and correctly mapping the 4-bit input to one of sixteen unique outputs.

Loading lesson…