TAK - L05

• Microprocessor system structure

  
• Typical microprocessor system consists of the following
• Typical microprocessor system consists of the following elements

  • microprocessor,
  • RAM,
  • ROM,
  • I/O systems,
  • devices for the transmission of information,
  • external devices
• Microprocessor


  Processes data by performing arithmetic and logical operation based on commands read from memory. It's the CPU
• The main functional assemblies of the microprocessor:

  • registers
  • ALU
  • controls
• RAM

  1. Used to store currently processed data and the program
  2. volatile
  3. the memory chip was placed directly on the board in the initial period, currently it is mounted on memory modules
• ROM contains:

  • POST
  • BIOS
  • Bootstrap loader
• Rom chips are slow - access time of 150 ns
• POST


  Power-On Self test

  Tests of individual computer components
• Bootstrap Loader

  A program that searches for and loads the operating system into the operating memory
• Computer buses


  A bus is a collection of paths conducting electrical signals. The data takes two values: 0 or 1.

  The more signal lines part of the bus, the more bits can be transmitted in one unit of time
• Buses types

  • Data
  • Control
  • Address
• Data bus 


  Is the CPU bus. They transfer data between the processor and memory or I/O chips
• Examples of data bus characteristics

  • 8088 - 8-bit bus
  • 8086-386SX - 16-bit bus
  • 396DX- 486 - 32-bit bus
  • Pentium and above - 64-bus
• Data bus width determines the systems overall performance
• Control bus

  it transmits signals controlling the operation of other components in they system and information signals for the processor
• Examples of control signals:

  • write to memory
  • reading from memory
  • write to I/O port
  • reading from I/O port
  • confirmation of transfer
  • bus request
  • transfer of control over the bus
  • interrupt request
  • interrupt ACK
• Adress bus 


  A set of lines that carry information about the address in memory or the I/O chip to which data is transmitted or retrieved. The number of lines is related to the procesor's address space
• n = number of lines. Number of addresses = $2^n$
• Address bus

  
• Reading data from memory or from the input device

  
• Write data to memory or input device

  
• Internal memories used in microcomputer systems should be characterised by:

  • high speed of operation
  • low power consumption
  • small dimensions
• Basic memory parameters:

  • capacity
  • access time
• Memory

  
• ROMs are also found on expansion cards(auxiliary programs and drivers required by the card)
• ROM 


  Memories are programmed in the technological process. it is impossible to change the program once saved
• PROM - programmable ROM


  User-programmable memory. it is impossible to change the program once saved
• EPROM - Erasable PROM

  It is programmed by the user. The memory can be erased by ultraviolet exposure, after which it is possible to reprogram it
• EEPROM - Electrically EPROM


  Erasing is done electronically. in this group, there are flash memories
• PROM

  single-write computer memory, built as an integrated circuit

  Programming PROM memory consists in giving between the bit line and the word line voltage from a dozen to several dozen volts, which burns the element connecting the bit line and the word line. The resistor burns out for a break, and the transistors for a short circuit. memories with a resistance matrix have entered 1, when we are programming we enter 0. Memories with a transistor matrix have 0. The programming process does not take place at the time of production
• EPROM

  Programmed by applying voltage higher than usually used to the transistor drain. it is capable of temporarily piercing a thing insulating layer around the remembering gate and letting a specific electric charge into it. its presence permanently clogs the transistor, regardless of the state of the second gate.
• Once stored, EPROM can be erased by exposing it to strong ultraviolet light(253.7nm) which ionises the insulator allowing the accumulated charge to flow away
• EEPROM 


  Can be repeatedly written an cleaned using electric current, yet the number of writes in limited, while the number of memory readings is arbitrary
• EEPROM is used to write the BIOS ro row computer's motherboard
• EEPROM - flash

  Allows you to save or delete multiple memory cells in a single programming operation. it is a non-volatile memory.

  Standard EEPROMS allow you to save or erase only one memory cell at the time, which means flash is much faster.

  Flash memory is produced in two versions: NOR and NAND
• DRAM

  type of RAM used in computers as an operating memory, that stores each bit od data in a separator capacitors

  since capacitors tent to discharge, they are periodically refreshed by a specialised refresh system that provides additional refresh pulses every few/several dozen ms. this is called memory refers
• DRAM chips are very complicated, but their advantage is low cost and small size
• SRAM


  used as fast memory for microcomputer systems and devices.

  SRAM stores data for as long as the power is on

  each bit is stores in a system consisting of four transistors (flip-flop) and two control transistors. this structure allows faster bit reading and does not require refreshing
• Dynamic memory access modes

  • Page mode - separate row addressing and column addressing for each cycle
  • FPM Fast Page Mode - capable of working with bus freq up to 66MHz. Simplification of the addressing mechanism
  • EDO Extended Data Output - based on FPM systems. equipped with a mechanism that allows you to issue another address on the address bus already during the reading of data. this results in shorter access times