Microprocessors Ch1. the Architecture of a Microcomputer - HC 2016 v2

8/15/2019 Microprocessors Ch1. the Architecture of a Microcomputer - HC 2016 v2

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Horia Cucu

Speech & Dialogue Research Laboratory Faculty of Electronics, Telecommunications and Information Technology

University POLITEHNICA of Bucharest





1.1 Definitions



Block Diagram of a Microcomputer

03.03.2016 4Microprocessor Architectures

A microcomputer is a general purpose device that can be programmedto carry out a set of arithmetic and/or logical operations.



Functional Components

CPU: the hardware block which processes data andcontrols the system

Memory: the hardware block which stores data in asequence of memory locations

I/O devices: hardware blocks that form the interface

between the microcomputer and the external world

Busses: the connections between the above blocks




The von Neumann Principles

Both data and instructions are stored in the memory

The contents of the memory is accessed by location

The microprocessor is the CPU of the microcomputer; its role isto process data and control the system

The instructions are fetched from the memory and executedsequentially by the CPU

I/O ports are used to communicate with other devices

The three hardware blocks are interconnected by the system bus




The Memory – Basic Principles

Memory – sequence of memory locations used to store info Each memory location:

stores an 8-bit number, a byte of data

is identified by a unique number, called address

The memory is accessed and organized by the CPU only

The CPU can choose to create logical subdivisions within thememory (called pages or segments)

The memory map – all memory locations that can beaddressed by the CPU (not necessarily implemented)

The size of the memory map – performance criterion




The Memory – A Closer Look




The Memory – A Closer Look

The size of the memory is directly linked with the addresssize through the following equation:

Example 1: using an address of 2 bits, one can form 4 different addresses:

00, 01, 10, and 11, for up to 4 different memory locations consequently, a memory with an address of 2 bits will

comprise 4 memory locations (4 bytes).

Example 2: using a 20-bit address, one can form 220 different addresses,

corresponding to 220 different memory locations

consequently, a memory with a 20-bit address will comprise220 memory locations (1 MB).


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bitseaddressSiz memorySize



The Memory – Contents Significance


This could be a 16-bit result

This could be an instruction

These could be the first two elements inan array of 8-bit numbers

• The significance of the information is given by the programmer.

• The memory “doesn’t know” the significance of the information it stores!



Input/Output Devices

I/O Devices – hardware blocks that form the interfacebetween the microcomputer and the external world

I/O Devices – can be regarded as a set of I/O Ports

Each I/O port can be used to: send an 8-bit/16-bit/32-bit number to an external device

receive an 8-bit/16-bit/32-bit number from an external device

is identified by a unique number, called port address

The ports map – all ports that can be addressed by the CPU(not necessarily implemented)

The size of the ports map – performance criterion






The Software Component

The microcomputer is executing instructions organized incomputer programs, namely the software

Two main categories: The Operating System: set of programs which facilitate the

user’s access to the system’s resources

User Software: set of programs specifically created by the user

to achieve a certain task




Summary


The CPU: executes instructions (processes data) and controls the system

The Memory: stores both the data and the instructions

The I/O Devices: interconnect the microcomputer with the outside world



1.2 Information Representation in Computer Systems



Information Representation in

Computer Systems


Information is stored using electronic circuits, called flip-flops (or bistables), that have two stable states: on/off

The state of a bistable can be used to represent a bit (i.e.binary digit: 0, 1) or a boolean value (true, false)

Data types with more than two possible values are stored

using sequences of bits: Byte (B) – a sequence of 8 bits: can store max 28 (256) values

Word (w) – a sequence of 16 bits: can store max 216 values

Double word (dw) – 32 bits: can store max 232 values



The binary, decimal

and hexadecimal bases


Any sequence of bits can also be represented as: a decimal number (number in base 10)

can be written as a sequence of decimal digits (0, 1, …, 9)

a hexadecimal number (number in base 16) can be written as a sequence of hexadecimal digits (0, 1, …, 9, A,

B, C, D, E and F)

Hexadecimal numbers representation conventions:

the “h” suffix: 1A44h the “0x” prefix: 0x1A44

Conversion algorithms

binary decimal

hex



Numbers representation


Unsigned (positive) integer numbers

“Natural binary” representation

Signed integer numbers “Sign & magnitude” representation

“1’s complement” representation

“2’s complement” representation

Signed real numbers

“Fixed point” representation

“Floating point” representation



Integer numbers representation


Decimal

value Sign and magnitude 1’s complement 2’s complement

5 natural binary: 00000101 natural binary: 00000101 natural binary: 00000101

-5natural binary: 00000101

flip the sign bit: 10000101

natural binary: 00000101

flip all bits: 11111010



add 1: 11111011

12 natural binary: 00001100 natural binary: 00001100 natural binary: 00001100

-12natural binary: 00001100

flip the sign bit: 10001100





add 1: 11110100



Real numbers representation


“Fixed point” representation

A fixed sequence of bits is used to represent decimal part

Two’s complement representation

A fixed sequence of bits is used to represent the fractional part

Natural binary representation

“Floating point” representation

A fixed sequence of bits is used to represent the mantissa

Two’s complement representation A fixed sequence of bits is used to represent the exponent

Natural binary representation

Example: real number = mantissa × 2exponent



Characters representation


Codingconventions:

ASCII

UTF-8 UTF-16

Unicode



Instructions are represented using sequences of bytes; Some processors have fixed-size instructions

8086 has variable-size instructions (1-6 bytes)

The instruction codes are formed of several fields:

one field representing the instruction type

none, one or several fields representing data

none, one or several fields representing addresses are associated with mnemonics (to be used in programming)

Example: add AX, 8017h <=> 051780h

Programs representation


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Microprocessors Ch1. the Architecture of a Microcomputer - HC 2016 v2