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Provides a comprehensive overview of different types of registers, their construction, and their applications in digital circuits. ​

Objectives

  • Introduction to registers and their types
  • Explanation of simple 4-bit registers and 4-bit registers with load control
  • Overview of various shift registers
  • Discussion on bidirectional and special shift registers, including ring counters and Johnson counters

Introduction

  • A flip-flop stores one bit of information, while a register stores multiple bits using multiple flip-flops.
  • Registers are used for data storage, movement, and processing operations.
  • Common types of registers include simple registers, shift registers, and parallel access shift registers.

Simple 4-Bit Register

  • Constructed using D flip-flops.
  • Stores 4 bits of data with parallel input and output.

4-Bit Register with Load Control

  • Similar to a simple 4-bit register but includes a load control feature to manage data loading.

Shift Registers

  • Used for storage and transfer of digital data.
  • Consist of flip-flops connected in a chain, with the output of one flip-flop becoming the input of the next.
  • Types of shift registers:
    • Serial In – Serial Out (SISO): Data is entered and shifted out serially.
    • Serial In – Parallel Out (SIPO): Data is entered serially and outputted in parallel.
    • Parallel In – Serial Out (PISO): Data is entered in parallel and shifted out serially.
    • Parallel In – Parallel Out (PIPO): Data is entered and outputted in parallel.
    • Bidirectional Shift Registers: Data can be shifted left or right.

Serial In – Serial Out (SISO) Shift Registers

  • Data is entered sequentially and shifted through the register.
  • Can be read destructively (data is lost) or non-destructively (data is preserved).

Serial In – Parallel Out (SIPO) Shift Registers

  • Data is entered serially, but all bits are available simultaneously at the output.

Parallel In – Serial Out (PISO) Shift Registers

  • Data is entered in parallel and shifted out serially.
  • Uses D flip-flops and NAND gates for data entry.

Parallel In – Parallel Out (PIPO) Shift Registers

  • Data is entered and outputted in parallel.
  • All data bits appear at the outputs simultaneously after being clocked in.

Bidirectional Shift Registers

  • Can shift data left or right.
  • Right shift divides the binary number by two, while left shift multiplies it by two.
  • Uses NAND gates configured as OR gates for selecting data inputs.

Special Shift Registers

  • Ring Counter: A circulating shift register where the output of the most significant stage is fed back to the input of the least significant stage. It is self-decoding and operates in a mode-4 sequence.
  • Johnson Counter: A variation of the ring counter with the inverted output of the last stage fed back to the input of the first stage. It operates in a mod-2n sequence.

Registers – Lesson 8

Engineering Institute of Technology