Computer Organization and Architecture

Microcontrollers and Microprocessors

• A microcontroller is a multipurpose PLD that accepts binary data as input.
• The heart of a CPU is a microprocessor.
• A microcontroller consists of a CPU, on-chip RAM, on-chip ROM, I/O ports, and timers.
• Microcontrollers are used in computers, laptops, televisions, printers, refrigerators, and microwave ovens.

Memory and Addressing

• The basic element of memory is a flip-flop.
• A microprocessor with 'n' address lines can directly address 2^n memory locations.
• To store programs and data, memory is used.
• Registers can be classified into RAM and ROM, with RAM being volatile memory.
• WR' is the signal used to write data into a RAM location.

Number of Locations and Address Lines

• A 4*8-bit register has 4 locations.
• A microcontroller with 16 address lines has a ROM capacity of 65536.
• 10 address lines are required to access 1kB of ROM.
• A memory IC with 10 address lines pins will have 1024 memory locations.

Microcontrollers and Their Features

• The 8051 is an 8-bit microcontroller with 40 pins.
• The size of the data bus in 8051 is 8 bits, and the size of the address bus is 16 bits.
• The accumulator size in 8051 is 8 bits, and the program counter is 16-bit wide.
• The ALU size in 8051 is 8 bits.
• PSW stands for Program Status Word.

Input/Output Operations

• To select external memory in 8051, the EA pin is used.
• ALE stands for Address Latch Enable, and PSEN stands for Program Store Enable.
• There are four parallel I/O ports available in 8051 microcontrollers.
• Port 0 and Port 2 act as 16-bit address lines for transferring data through them.

Control Unit and Instruction Cycle

• The control unit generates control signals necessary for the execution of an instruction.
• The control unit is responsible for the flow of data and instructions within the computer.

Technology and Generations

• The 8085 is an 8-bit microprocessor.
• 2nd generation microprocessors are fabricated with NMOS technology.
• 3rd generation microprocessors are fabricated with HMOS technology and are 16-bit processors.
• 4th generation microprocessors are 32-bit processors, and 5th generation microprocessors are 64-bit processors.
• IC 80386 microprocessors are fabricated with HCMOS technology.

Applications

• Microcontrollers are used in temperature control systems.
• PIC stands for Peripheral Interface Controller, and PIC16F877A is a type of microcontroller.
• The PIC16F877A has 40 pins, 33 I/O pins, and uses flash memory technology.
• The PIC16F877A has 368 bytes of RAM, 256 bytes of EEPROM, and 8KB of program memory.