The Microprocessor-based PC System

The Microprocessor-based PC System

Prima Dewi PurnamasariMicroprocessor

Electrical Engineering DepartmentUniversity 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

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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 1M less than 64G of extended memory


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?


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 = 000000HEnding address = 1FFFFFH


Memory Illustration

FFFFFH …………… …………… …………… …00002H …00001H 0111 0001

B00000H 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 TPAThe memory map (fig. 1.4, in hexadecimal addr.) shows how many areas of the TPA are used for system programs, data, and drivers


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 AreaThe 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


EMSThe area at locations C8000H-DFFFFH is often open or free. It is usually used for the Expanded Memory System (EMS) Fig.1.6The 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 deviceThe 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 device2. transfer data between an I/O device or

memory and the microprocessor3. control the I/O and memory system


BUSSESThree 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



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The Microprocessor-based PC System

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