Digital Components Notes | BTech Cs 2024

Last updated on July 14th, 2024 at 05:47 am

Digital Components Notes

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The following Digital Components Notes on the subject of Computer Organisation and Architecture will surely help you to achieve grace marks.

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Integrated Circuit

• An integrated circuit is a small silicon semiconductor crystal, called a chip, containing the electronic components for the digital gates.
  
• The various gates are interconnected inside the chip to form the required circuit.
  
• Digital circuits are constructed with integrated circuits.
  
• The chip is mounted in a ceramic or plastic container, and connections are welded by thin gold wines to external pins to form the integrated circuit.
  
• The number of pins may range from 14 in a small IC package to 100 or more in a larger package.

SSI Devices

• Small-Scale Integration (SSI) devices contain several independent gates in a single package.
• The inputs and outputs of the gates are connected directly to the pins in the package.
• The number of gates is usually less than 10 and is limited by the number of pins available in the IC.

MSI Devices

• Medium-Scale Integration (MSI) devices have a complexity of approximately 10 to 200 gates in a single package.
• They usually perform specific elementary digital functions such as decoders, adders, and registers.

LSI Devices

• Large-Scale Integration (LSI) devices contain between 200 and a few thousand gates in a single package.
• They include digital systems, such as processors, memory chips, and programmable modules.

VLSI Devices

• Very-Large-Scale Integration (VLSI) devices contain thousands of gates within a single package.
• Examples are large memory arrays and complex microcomputer chips.
• They have small size and low cost.
• They revolutionized computer system design technology.

Digital integrated circuits are classified also by specific circuit technology called the digital logic family to which they belong. Some of them are:-

• Transistor-transistor logic (TTL)
• Emitter-coupled logic (ECL)
• Metal-oxide semiconductor (MOS)
• Complementary metal-oxide-semiconductor (CMOS)

TTL Family

• It was an evolution of a previous technology that used diodes and transistors for the basic NAND gate.
• It was called DTL – “diode-transistor logic.”
• The diodes were replaced by transistors to improve the circuit operation.
• That’s why ‘transistor’ is mentioned twice.
• Variations include – standard TTL, high-speed TTL, low-power TTL, Schottky TTL, low-power Schottky TTL, and advanced Schottky TTL.
• The power supply voltage is 5 volts, and the two logic levels are approximately 0 and 3.5 volts.

ECL Family

• It provides the highest-speed digital circuits in an integrated form.
• Used in systems such as supercomputers and signal processors where high speed is essential.
• The transistors in ECL gates operate in a nonsaturated state, a condition that allows the achievement of propagation delays of 1 to 2 nanoseconds.

MOS Family

• It’s a unipolar transistor depending on the flow of only one type of carrier, which may be electrons (n-channel) or holes (p-channel).
• Different from the bipolar transistor used in TTL and ECL gates, where both carriers exist during normal operation.
• A p-channel MOS is referred to as PMOS and an n-channel as NMOS.
• NMOS is used in circuits with only one type of MOS transistor.

CMOS Family

• It uses PMOS and NMOS transistors connected in a complementary fashion in all circuits.
• It has a high packing density of circuits.
• It has a simpler processing technique during fabrication.
• It has economical operation because of low power consumption.

Decoders

• A decoder is a combinational circuit that converts binary information from the n-coded inputs to a maximum of 2ⁿ unique outputs.
  
• A decoder has n inputs and m outputs and is also referred to as an n x m decoder.
  
• The three data inputs, A_o, A₁, and A₂ are decoded into eight outputs, each output representing one of the combinations of the three binary input variables.
  
• The three NOT gates provide the complement of the inputs.
  
• Each of the eight AND gates generates one of the binary combinations.
  
• It has one Enable input, E. The decoder is enabled when E is equal to 1 and disabled when E is equal to 0.

Multiplexers

• A multiplexer is a combinational circuit that receives binary information from one of 2ⁿ input data lines and directs it to a single output line.
  
• A 2ⁿ-to-1 multiplexer has 2ⁿ input data lines and n input selection lines whose bit combinations determine which input data are selected for the output.
  
• Example :- A 4×1 Multiplexer will have
  • 4 data inputs I₀ to I
  • 2 selection inputs S₀ and S₁

Register

• A register is a group of flip-flops with each flip-flop capable of storing one bit of information.
  
• A register may have combinational gates that perform certain data-processing tasks.
  
• A register with n flip-flops can store binary information of n-bits.
  
• It is a fast memory used to accept, store, and transfer data and instructions that are being used immediately by the CPU.
  
• The transfer of new information into a register is referred to as loading the register.
  
• Types of registers: –
  • MAR – Memory Address Register
  • AC – Accumulator
  • PC – Program Counter
  • IR – Instruction Register
  • MDR – Memory Data Register
  • R₁, R₂, … , R_n – General Purpose Register

Final Words

From the above article, you must have gained knowledge about Digital Components. We hope that with the help of these notes you will be successful.

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