01 introduction to_microprocessor

The Microprocessor-based PC
System
Prima Dewi Purnamasari
Microprocessor
Electrical Engineering Department
University of Indonesia

What is Computer?
• Basically, there are 3 components to build a
computer, and those three are interconnected
with wires. Could you name it?
Microprocessor (c) Prima Dewi Purnamasari 2011 2
? ??

General Block Diagram of
the PC
Fig. 1.2 shows the general block diagram of the PC
3Microprocessor (c) Prima Dewi Purnamasari 2011

Memory Microprocessor I/O
BUS

MICROPROCESSOR

The Microprocessor
• The microprocessor is the controlling element
in a computer system and is sometimes
referred to as the CPU (Central Processing Unit)
• Memory and I/O are controlled through
instructions that are stored in the memory and
executed by the microprocessor

• The microprocessor performs three main
tasks for the computer system:
1. Data transfer between itself and the memory or
I/O systems
2. simple arithmetic & logic operations (Table 1.3)
3. program flow via simple decisions (Table 1.4)
The Microprocessor

The Microprocessor
• Why the microprocessor is powerful?
– Able to execute millions of instructions per
second from a program or software (group of
instructions) stored in the memory system
– able to make simple decision, based upon
numerical facts (Table 1.4)

MEMORY

Memory
• The memory system is divided into three main
parts:
– TPA (Transient Program Area)
– system area,
– XMS (Extended Memory System) (optional)

Memory System
• The first 1M byte of memory  the
real/conventional memory system. Intel mP is
designed to function this area in real mode of
operation
• 80286  Pentium 4 contain not only real
memory, but also extended memory
• The Pentium Pro-based computer system, for
example, can have up to 1M less than 4G or 1 M
less than 64G of extended memory (Fig. 1.3)

Memory Address
• In Hexadecimal format
• 1MByte Real Memory:
= 220 x 1 Byte
= 1 0000 0000 0000 0000 0000 B x 1 Byte
• Each block of memory holds 1 Byte (8 bits) data
• 1MByte memory address:
– Starting address (#1) : 00000H
– Ending address (#220) : FFFFFH

Trivia
• How if 2MByte Memory? What is the starting and
ending address?
• 2MB = 221
= 1 1111 1111 1111 1111 1111 (21 x 1)
= 1FFFFF H
Starting address = 000000H
Ending address = 1FFFFFH

Memory Illustration
FFFFFH …
………… …
………… …
………… …
00002H …
00001H 0111 0001 B
00000H 0AH
Memory
Address
Each block of memory contains 1 Byte or 8 bits data

Memory System

Transient Program Area (TPA)
• Holds the OS and other program that control
the computer system
• Stores any currently active or inactive
application programs
• The length of TPA is 640 KB

Memory map of TPA
The memory map (fig.
1.4, in hexadecimal
addr.) shows how many
areas of the TPA are used
for system programs,
data, and drivers
Microprocessor (c) Prima Dewi Purnamasari 2011
19

TPA
• The interrupt vectors access various features of
the DOS, BIOS (Basic I/O System), and
application
• The BIOS and DOS communications areas
contain transient data used by program to
access I/O devices and internal features of the
computer system

TPA
• The IO.SYS is a program that loads into the TPA from
the disk whenever an MSDOS or PC DOS system is
started
• The MSDOS (PCDOS) program occupies two areas of
memory
• The size of the driver area and # of drivers change
from one computer to another

TPA
• The COMMAND.COM program controls the operation
of the computer from the keyboard when operated in
DOS mode
• The free TPA area holds application programs as they
are executed

System Area
The system area
(Fig. 1.5) contains
program on either
a read-only
memory or flash
memory and also
areas of
read/write (RAM)
memory for data
storage

EMS
The area at
locations C8000H-
DFFFFH is often
open or free. It is
usually used for the
Expanded Memory
System (EMS) 
Fig.1.6
The EMS allows a
64 KB page frame
of memory to be
used by application
programs

I/O

Input Output (I/O)
The input/output space
extends from I/O port 0000H
to port FFFFH.
An I/O port is similar to a
memory address but
addresses an I/O device
The I/O area contains two
major sections (Fig 1.7):
• the area below I/O location
0500H is reserved for
system devices
• the remaining area is
available I/O space for
expansion

BUS

Buses
• A bus is a set of common connections (wires )
that interconnect components in a computer
system and carry the same type of information
• Function:
1. select an I/O or memory device
2. transfer data between an I/O device or memory
and the microprocessor
3. control the I/O and memory system

BUSSES
Three buses exist for the transfer of information:
1)address,
2)data,
3)control

Buses (cont’d)
• The control bus contains lines that select the
memory or I/O and cause them to perform a
read or write operation.
• Four control bus connections: MRDC, MWTC,
IORC, IOWC
• The address bus requests a memory location
from the memory or an I/O location from the
I/O devices

Buses (cont’d)
• Example the micro-instructions for
READ:
1. the p reads the contain of memory
location by sending the memory an
address through address bus
2. the p sends the memory read control
signal (MRDC) to cause memory to read
data via control bus
3. the data read from the memory are
passed to the microprocessor through
the data bus

Buses (cont’d)
• The (maximum) memory sizes and organizations
differ between various member of the Intel p
family
• Data bus size defines the amount of data can be
transferred at a time (8, 16, 32, 64 bit)
• Address bus size corresponds to (maximum)
memory size can be attached to the
microprocessor
• Table 1.5 depicts a complete listing of bus and
memory sizes on the Intel family of p

NUMBER SYSTEMS
Self reading…

01 introduction to_microprocessor

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