Micro-Computer Applications:Number system & 8086 Organization

Dr. Eng. Amr T. Abdel-Hamid

ELECT 707

Fall 2011

Dr. A

mr T

alaat

ELECT 707

Micro

-Co

mp

uter A

pp

lication

s

The Microprocessor Age World’s first microprocessor the Intel 4004. A 4-bit microprocessor-programmable controller

on a chip. Addressed 4096, 4-bit-wide memory locations.

a bit is a binary digit with a value of one or zero4-bit-wide memory location often called a

nibble The 4004 instruction set contained 45 instructions.

Dr. A

mr T

alaat

ELECT 707

Micro

-Co

mp

uter A

pp

lication

s

Main problems with early microprocessor were speed, word width, and memory size.

Evolution of 4-bit microprocessor ended when Intel released the 4040, an updated 4004. operated at a higher speed; lacked

improvements in word width and memory size Texas Instruments and others also produced 4-bit

microprocessors. still survives in low-end applications such as

microwave ovens and small control systemsCalculators still based on 4-bit BCD (binary-

coded decimal) codes

Dr. A

mr T

alaat

ELECT 707

Micro

-Co

mp

uter A

pp

lication

s

Intel released 8008 in 1971.extended 8-bit version of 4004 microprocessor

Addressed expanded memory of 16K bytes.A byte is generally an 8-bit-wide binary number

and a K is 1024. memory size often specified in K bytes

Contained additional instructions, 48 total. Provided opportunity for application in more

advanced systems.engineers developed demanding uses for 8008

Dr. A

mr T

alaat

ELECT 707

Micro

-Co

mp

uter A

pp

lication

s

Intel introduced 8080 microprocessor in 1973.first of the modern 8-bit microprocessors

Motorola Corporation introduced MC6800 microprocessor about six months later.

8080—and, to a lesser degree, the MC6800—ushered in the age of the microprocessor.other companies soon introduced their own

versions of the 8-bit microprocessor

Dr. A

mr T

alaat

ELECT 707

Micro

-Co

mp

uter A

pp

lication

s

Only Intel and Motorola continue to create new, improved microprocessors.

IBM also produces Motorola-style microprocessors

Motorola sold its microprocessor division.now called Freescale Semiconductors, Inc.

Zilog still manufactures microprocessors. microcontrollers and embedded controllers

instead of general-purpose microprocessors

Dr. A

mr T

alaat

ELECT 707

Micro

-Co

mp

uter A

pp

lication

s

The Modern Microprocessor In 1978 Intel released the 8086; a year or so later,

it released the 8088. Both devices are 16-bit microprocessors.

executed instructions in as little as 400 ns (2.5 millions of instructions per second)

major improvement over execution speed of 8085

8086 & 8088 addressed 1M byte of memory.16 times more memory than the 80851M-byte memory contains 1024K byte-sized

memory locations or 1,048,576 bytes

Dr. A

mr T

alaat

ELECT 707

Micro

-Co

mp

uter A

pp

lication

s

Increased memory size and additional instructions in 8086/8088 led to many sophisticated applications.

Improvements to the instruction set included multiply and divide instructions.missing on earlier microprocessors

Number of instructions increased. from 45 on the 4004, to 246 on the 8085over 20,000 variations on the 8086 & 8088

Dr. A

mr T

alaat

ELECT 707

Micro

-Co

mp

uter A

pp

lication

s

These microprocessors are called CISC (complex instruction set computers).additional instructions eased task of developing

efficient and sophisticated applications 16-bit microprocessor also provided more internal

register storage space. Popularity of Intel ensured in 1981 when IBM

chose the 8088 in its personal computer.

Dr. A

mr T

alaat

ELECT 707

Micro

-Co

mp

uter A

pp

lication

s

THE MICROPROCESSOR-BASED PERSONAL COMPUTER SYSTEM

Computers have undergone many changes recently. Machines that once filled large areas reduced to

small desktop computer systems becauseof the microprocessor. although compact, they possess computing

power only dreamed of a few years ago

Dr. A

mr T

alaat

ELECT 707

Micro

-Co

mp

uter A

pp

lication

s

  The block diagram of a microprocessor-based computer system.

a bus is the set of common connections that carry the same type of information

Dr. A

mr T

alaat

ELECT 707

Micro

-Co

mp

uter A

pp

lication

s

The Microprocessor Called the CPU (central processing unit). The controlling element in a computer system. Controls memory and I/O through connections

called buses.buses select an I/O or memory device, transfer

data between I/O devices or memory and the microprocessor, control I/O and memory systems

Memory and I/O controlled via instructions stored in memory, executed by the microprocessor.

Dr. A

mr T

alaat

ELECT 707

Micro

-Co

mp

uter A

pp

lication

s

Microprocessor performs three main tasks:data transfer between itself and the memory or

I/O systemssimple arithmetic and logic operationsprogram flow via simple decisions

Power of the microprocessor is capability to execute billions of millions of instructions per second from a program or software (group of instructions) stored in the memory system.stored programs make the microprocessor and

computer system very powerful devices

Dr. A

mr T

alaat

ELECT 707

Micro

-Co

mp

uter A

pp

lication

s

Another powerful feature is the ability to make simple decisions based upon numerical facts.a microprocessor can decide if a number is

zero, positive, and so forth These decisions allow the microprocessor to

modify the program flow, so programs appear to think through these simple decisions.

Dr. A

mr T

alaat

ELECT 707

Micro

-Co

mp

uter A

pp

lication

s

Buses A common group of wires that interconnect

components in a computer system. Transfer address, data, & control information

between microprocessor, memory and I/O. Three buses exist for this transfer of information:

address, data, and control. Figure 1–12 shows how these buses interconnect

various system components.

Dr. A

mr T

alaat

ELECT 707

Micro

-Co

mp

uter A

pp

lication

s

Figure 1–12  The block diagram of a computer system showing the address, data, and control bus structure.

Dr. A

mr T

alaat

ELECT 707

Micro

-Co

mp

uter A

pp

lication

s

The address bus requests a memory location from the memory or an I/O location from the I/O devices. if I/O is addressed, the address bus contains a

16-bit I/O address from 0000H through FFFFH. if memory is addressed, the bus contains a

memory address, varying in width by type ofmicroprocessor.

64-bit extensions to Pentium provide 40 address pins, allowing up to 1T byte of memory to be accessed.

Dr. A

mr T

alaat

ELECT 707

Micro

-Co

mp

uter A

pp

lication

s

The data bus transfers information between the microprocessor and its memory and I/O address space.

Data transfers vary in size, from 8 bits wide to 64 bits wide in various Intel microprocessors. 8088 has an 8-bit data bus that transfers 8 bits

of data at a time8086, 80286, 80386SL, 80386SX, and 80386EX

transfer 16 bits of data80386DX, 80486SX, and 80486DX, 32 bits Pentium through Core2 microprocessors transfer

64 bits of data

Dr. A

mr T

alaat

ELECT 707

Micro

-Co

mp

uter A

pp

lication

s

Organization of 8088

AH AL

BH BL

CH CL

DH DL

SP

BP

SI

DI

ALU

Flag register

Execution Unit (EU)

EU control

CS

DS

SS

ESALU Data bus (16 bits)

Address bus (20 bits)

Instruction Queue

Bus control

External bus

IP

Data bus(16 bits)

Bus Interface Unit (BIU)

General purpose register

Segment register

Dr. A

mr T

alaat

ELECT 707

Micro

-Co

mp

uter A

pp

lication

s

General Purpose Registers

15 8 7 0

AX

BX

CX

DX

AH AL

BH BL

CH CL

DH DL

Accumulator

Base

Counter

Data

SP

BP

SI

DI

Data Group

Pointer and Index Group

Stack Pointer

Base Pointer

Source Index

Destination Index

Dr. A

mr T

alaat

ELECT 707

Micro

-Co

mp

uter A

pp

lication

s

Microprocessors 3-21

Arithmetic Logic Unit (ALU)

n bits n bits

A B

Y

F

Carry

Y= 0 ?

A > B ?

F Y

0 0 0 A + B0 0 1 A - B0 1 0 A - 1

0 1 1 A and B

1 0 0 A or B

1 0 1 not A

Signal F control which function will be conducted by ALU.

Signal F is generated according to the current instruction.

Basic arithmetic operations: addition, subtraction, Basic logic operations: and, or, xor, shifting,

Dr. A

mr T

alaat

ELECT 707

Micro

-Co

mp

uter A

pp

lication

s

Flag Register

OFDF IF TF ZFSF AF PF CF 015

Control Flags Status Flags

IF: Interrupt enable flagDF: Direction flagTF: Trap flag

CF: Carry flagPF: Parity flagAF: Auxiliary carry flagZF: Zero flagSF: Sign flagOF: Overflow flag

Flag register contains information reflecting the current status of a microprocessor. It also contains information which controls the operation of the microprocessor.

Dr. A

mr T

alaat

ELECT 707

Micro

-Co

mp

uter A

pp

lication

s

Instruction Machine Codes Instruction machine codes are binary numbers

For Example:

1 0 0 0 1 0 0 0 1 1 0 0 0 0 1 1 MOV AL, BL

MOV Machine code structure

Opcode Operand1

Opcode tells what operation is to be performed.EU control logic generates ALU control signals according to Opcode)

Some instructions do not have operands, or have only one operand

Operands tell what data should be used in the operation. Operands can

be addresses telling where to get data (or where to store results)

Registermode

Mode Operand2

Mode indicates the type of a instruction: Register type, or Memory type

Dr. A

mr T

alaat

ELECT 707

Micro

-Co

mp

uter A

pp

lication

s

EU Operation1. Fetch an instruction from instruction queue

2. According to the instruction, EU control logic generates control signals.

(This process is also referred to as instruction decoding)

3. Depending on the control signal, EU performs one of the following operations:

An arithmetic operation A logic operation

Storing a datum into a register Moving a datum from a register

Changing flag register

Dr. A

mr T

alaat

ELECT 707

Micro

-Co

mp

uter A

pp

lication

s

Registers

A register is a storage element inside a microprocessor.

Almost all operations would involve using registers.

Some registers are general purpose registers, while others have special purposes.General purpose registers can hold various

data sizes and used for almost any purpose as dictated by the program.

However, each general purpose register does have its own special purposes.

Dr. A

mr T

alaat

ELECT 707

Micro

-Co

mp

uter A

pp

lication

s

Registers

Dr. A

mr T

alaat

ELECT 707

Micro

-Co

mp

uter A

pp

lication

s

Registers

Since the x86 instruction set is designed to be compatible with previous microprocessors, the same register can be accessed using different names.Different names are given for 64-bit, 32-bit, 16-bit and 8-bit version of the same register.

Dr. A

mr T

alaat

ELECT 707

Micro

-Co

mp

uter A

pp

lication

s

General Purpose Registers

RAX, EAX, AX (AH & AL)A general purpose register Also an accumulator – stores intermediate

results after arithmetic and logic operationsCan also hold the offset address of a location

in memory (80386 and above)RBX, EBX, BX (BH & BL)

A general purpose registerAlso a base index register – holds the offset

address of a location in memoryCan also address memory data (80386 and

above)

Dr. A

mr T

alaat

ELECT 707

Micro

-Co

mp

uter A

pp

lication

s

General Purpose Registers

RCX, ECX, CX (CH & CL)A general purpose registerAlso a count register – holds the count for

various instructionsCan also hold the offset address of a location

in memory (80386 and above)RDX, EDX, DX (DH & DL)

A general purpose registerAlso a data register – stores data related to

accumulator’s calculation (multiply and divide)

Can also address memory data (80386 and above)

Dr. A

mr T

alaat

ELECT 707

Micro

-Co

mp

uter A

pp

lication

s

General Purpose Registers

RBP, EBP, BPA general purpose registerAlso a base pointer register – points to a

memory location for memory data transfer RDI, EDI, DI

A general purpose registerAlso a destination index register – holds the

memory address for the destination data of a string instruction

Dr. A

mr T

alaat

ELECT 707

Micro

-Co

mp

uter A

pp

lication

s

General Purpose Registers

RSI, ESI, SIA general purpose registerAlso a source index register - holds the

memory address for the source data of a string instruction

R8 through R15General purpose registersFound only in 64-bit microprocessorsData are addressed in 64-, 32-, 16-, or 8-bit

sizes

Dr. A

mr T

alaat

ELECT 707

Micro

-Co

mp

uter A

pp

lication

s

Special Purpose Registers

RIP, EIP, IP Instruction pointer – points to the next

instruction in the memory to be executed

RSP, ESP, SPStack pointer – points to an area in memory

called the stack

RFLAGS, EFLAGS, FLAGS Indicates the condition of the microprocessor

and control its operation

Dr. A

mr T

alaat

ELECT 707

Micro

-Co

mp

uter A

pp

lication

s

Flags

Dr. A

mr T

alaat

ELECT 707

Micro

-Co

mp

uter A

pp

lication

s

Flags

The C, P, A, Z, S and O flags are changed by most arithmetic and logic operations.

Flags never change for any data transfer or program control operations.

Some flags are also used to control features found in the microprocessor.

Dr. A

mr T

alaat

ELECT 707

Micro

-Co

mp

uter A

pp

lication

s

Flags

Descriptions for some of the flag bits:C (carry): holds the carry after addition or

borrow after subtraction.P (parity): the count of 1s in a number

expressed as even or odd.0 for odd, 1 for even.

A (auxiliary carry): holds the half-carry after addition or the borrow after subtraction between bit positions 3 and 4 of the result.

Dr. A

mr T

alaat

ELECT 707

Micro

-Co

mp

uter A

pp

lication

s

Flags

Z (zero): shows that the result of an arithmetic or logic operation is zero.0 result is not zero, 1 result is zero.

S (sign): holds the arithmetic sign of the result after an arithmetic or logic instruction executes.0 for positive, 1 for negative.

T (trap): enables trapping through an on-chip debugging feature.0 disable trapping, 1 enable trapping. If enabled, allows the microprocessor to interrupt

the flow of the program on conditions indicated by the debug registers and control registers.

Microsoft Visual Studio debugging tool uses this feature.

Dr. A

mr T

alaat

ELECT 707

Micro

-Co

mp

uter A

pp

lication

s

Flags

I (interrupt): control the operation of the INTR (interrupt request) input pin.0 disables INTR pin, 1 enables INTR pin.

D (direction): selects increment or decrement mode for SI/DI registers.0 increment, 1 decrement.

O (overflow): indicates that the result of an addition/subtraction of signed numbers exceeded the capacity of the machine.