Detail about 8085 microprocessor

what is a Microprocessor?

• A microprocessor is a clock-driven semiconductor device consisting of electronic logic circuits manufactured by using either a large-scale integration (LSI) or very-large-scale integration (VLSI) technique.
• The microprocessor is capable of performing various computing functions and making decisions to change the sequence of program execution.
• In large computers, a CPU performs these computing functions.The Microprocessor resembles a CPU exactly.
• The microprocessor is in many ways similar to the CPU, but includes all the logic circuitry including the control unit, on one chip.
• The microprocessor can be divided into three segments for the sake of clarity. – They are: arithmetic/logic unit (ALU), register array, and control unit.
• A comparison between a microprocessor, and a computer is shown below:
  
  
  • Arithmetic/Logic Unit: This is the area of the microprocessor where various computing functions are performed on data. The ALU unit performs such arithmetic operations as addition and subtraction, and such logic operations as AND, OR, and exclusive OR.
  • Register Array: This area of the microprocessor consists of various registers identified by letters such as B, C, D, E, H, and L. These registers are primarily used to store data temporarily during the execution of a program and are accessible to the user through instructions.
  • Control Unit: The control unit provides the necessary timing and control signals to all the operations in the microcomputer. It controls the flow of data between the microprocessor and memory and peripherals.
  • Memory: Memory stores such binary information as instructions and data, and provides that information to the microprocessor whenever necessary. To execute programs, the microprocessor reads instructions and data from memory and performs the computing operations in its ALU section. Results are either transferred to the output section for display or stored in memory for later use. Read-Only memory (ROM) and Read/Write memory (R/WM), popularly known as Random- Access memory (RAM).

  1. The ROM is used to store programs that do not need alterations. The monitor program of a single-board microcomputer is generally stored in the ROM. This program interprets the informat entered through a keyboard and provides equivalent binary digits to the microprocessor. Programs stored in the ROM can only be read; they cannot be altered.
  2. The Read/Write memory (RIWM) is also known as user memory It is used to store user programs and data. In single-board microcomputers, the monitor program monitors the Hex keys and stores those instructions and data in the R/W memory. The information stored in this memory can be easily read and altered.

  • I/O (Input/Output): It communicates with the outside world. I/O includes two types of devices: input and output; these I/O devices are also known as peripherals. 
    System Bus: The system bus is a communication path between the microprocessor and peripherals: it is nothing but a group of wires to carry bits.