AVR Microcontroller and Assembly Languagesaqazi.com/EEE342/FA19_MP_Lecture02_20190905...2019/09/05...

AVR Microcontroller

and Assembly

LanguageLecture# 02

Microprocessor System and Interfacing

Dr. Sohaib Ayyaz QaziCOMSATS University Islamabad

1

Lecture Objectives

About AVR Microcontroller

Microcontroller Architecture

Assembly Language


2

Harvard and Von Neumann Architectures

A Von Neumann architecture has only one bus which is used

for both data transfers and instruction fetches

Harvard architecture has separate data and instruction

busses, allowing transfers to be performed simultaneously on

both busses.


3

Microprocessors

A microprocessor incorporates the functions of

a computer's central processing unit (CPU) on a

single integrated circuit (IC), or at most a few integrated

circuits.

It is a multipurpose, programmable device that

accepts digital data as input, processes it according to

instructions stored in its memory, and provides results as

output.

It is an example of sequential digital logic, as it has internal

memory. Microprocessors operate on numbers and symbols

represented in the binary numerical system.

Examples Intel x86(286,386,486), Pentium series, Motorola

Power PC, Advance RISC Machine (ARM) Processor .

Microprocessor might only include an arithmetic logic

unit (ALU) and a control logic section.


4

Microprocessors

The ALU performs Arithmetic operations addition, subtraction,

and logical operations AND or OR.

Each operation of the ALU sets one or more flags in a status

register, which indicate the results of the last operation (zero

value, negative number, overflow. or others).

Control Unit retrieves instruction operation codes from

memory, and initiates whatever sequence of operations of the

ALU required to carry out the instruction.

A single operation code might affect many individual data

paths, registers, and other elements of the processor.


5

Microprocessor

A multi-core processor is simply a single chip containing

more than one processing cores.

This effectively multiplies the processor's potential

performance by the number of cores.

Some components, such as bus interface and cache,

may be shared between cores.

The cores are physically very close to each other, they

can communicate with each other much faster than

separate processors in a multiprocessor system, which

improves overall system performance.


6


7 Microprocessor

Microprocessor Architecture

A Comparison


8

Microprocessor Microcontroller

Choosing a Microcontroller

Microcontrollers are generally 8-bit.

Each controller has a unique instruction set and

register set and are not compatible with one

another.

Criteria to choose microcontroller include:

Meeting needs efficiently and cost effectively

Speed, Packaging, Power Consumption, RAM and ROM,

IO pins and timer, Cost per unit.

Hardware and software development tools

Availability and reliability of microcontroller sources


9

AVR Microcontroller

8-bit single-chip microcontroller with Harvard

Architecture

On-chip program ROM

Data RAM

EEPROM

Timers

I/O ports


10

AVR Microcontroller

Program ROM


11

Used to store programs

Size can vary from 1K to 256K

AVR is the first microcontroller to use on-chip Flash

memory

AVR Microcontroller

Data RAM and EEPROM


12

Used for data storage

It has general purpose registers, I/O memory and

internal SRAM

32 general purpose registers

Size of SRAM and I/O memory size varies

EEPROM stores critical data which does not need to

be changed

AVR Microcontroller

I/O Pins


13

Normally 3 to 86 pins for I/O purpose

Depends on package

The package size varies from 8 to 100 pins

AVR Microcontroller

Peripherals


14

ADC

Timers

USART

I2C

SPI

AVR Architecture and Programming


15

General Purpose Registers

AVR Data Memory

Instruction with Data Memory

AVR Status Register

AVR Data Format and Directives

AVR Assembly Programming

Assembling an AVR Program

Program Counter and Program ROM space


General Purpose Registers (GPRs)


16

Many registers to store data

Store information temporarily which is byte of data or address

pointing to data

In AVR there are 32 GPRs

Located at lowest of memory locations (address from 0x0000

to 0x001F

R0D7 D6 D5 D4 D3 D2 D1 D0

R1D7 D6 D5 D4 D3 D2 D1 D0

R2D7 D6 D5 D4 D3 D2 D1 D0

R31D7 D6 D5 D4 D3 D2 D1 D0


GPRs – LDI Instruction


17

Copies 8-bit data into general purpose registers

LDI Rd, K

K is an 8-bit value, Rd is any of the R16 to R31 registers

LDI loads right operand in left operand

I stands for “immediate”, provide data immediately

Remember that

To present a number in hex either use $ or 0x before anynumber. Otherwise it will be treated as a decimal.

If values from 0 to F are moved then rest of the bits will betreated as zeros.

If a larger value greater than 255 is moved then it will causean error


GPRs – LDI Instruction – Example


18

LDI R20, 0x20 ; load R20 with 0x20



LDI R25, $23 ; What is the value of R25?

LDI R31, 86 ; What is the value of R31?


GPRs – ADD Instruction


19

Adds the value of one register to the other

ADD Rd, Rr

Adds Rr with Rd and stores value in Rd


GPRs – ADD Instruction - Example


20

Add two numbers 0x25 and 0x34

LDI R16, 0x25

LDI R17, 0x34

ADD R16, R17

What is the value of R16?

What is the value of R17?


The AVR Data Memory


21

Used to store data

Divided in three parts

GPRs

I/O Memory

SRAM


The AVR Data Memory - GPRs


22

32 bytes of memory

Address are from $00 - $1F


The AVR Data Memory – I/O Memory


23

Used to control microcontroller peripherals such as

Status registers

Timers

Serial Communication

I/O Ports

ADC

Memory depends on number of pins available

At-least 64 bytes of memory is available for all AVRs


The AVR Data Memory – SRAM


24

Store any 8-bit wide data

Accessed by address directly

Total memory size is sum of all memories

EEPROM memory is used to store data permanently. It is not erased when power is off

Data Memory

(Bytes)

SFRs

(Bytes)

SRAM

(Bytes)

GPRs

(Bytes)

ATtiny25 224 64 128 32

ATtiny85 608 64 512 32

ATmega8 1120 64 1024 32

ATmega16 1120 64 1024 32

ATmega32 2144 64 2048 32

ATmega128 4352 64+160 4096 32

ATmega2560 8704 64+416 8192 32


Instruction with Data Memory


25

Instructions can be used to access different locations of data

memory


Instruction with Data Memory – STS


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STore direct to data Space

STS K, Rr

K is address location between 0x0000 and 0xFFFF

Rr to take data from

To copy contents of GPRs into an address location in data

space

This location can be any part of data space available

Example

STS 0x230, R25

What will happen when this instruction is executed?


Instruction with Data Memory – STS – Class Exercise


27

LDI R20, 0x99

STS 0x200, R20

STS 0x201, R20

STS 0x202, R20

STS 0x203, R20

What will be the result of these instructions ? Anyone who can fill

this table ?

Address Data

0x200

0x201

0x202

0x203


Instruction with Data Memory - LDS


28

Load Direct from data Space

LDS Rd, K

Rd data location to be stored

K is address between 0x0000 and 0xFFFF

Instruction tells CPU to copy one byte of data from address

location

This location can be any part of data space available

Example

LDS R5, 0x200

What will be the result of this instruction ?


Instruction with Data Memory – LDS – Class Exercise


29

Load two numbers in two GPRs

Store these numbers at locations 0x300 and 0x302

Add two numbers located at 0x300 and 0x302

R0 R1 Addr $300 Addr $302

Before LDS R0, 0x300 ? ? 12 13

After LDS R0, 0x300 12 ? 12 13

After LDS R1, 0x302 12 13 12 13

ADD R1, R0 25 13 12 13


Instruction with Data Memory – STS – Class Exercise


30

Put 0x45 to Ports B, C. The addresses of port B, C and D is 0x38,

0x35, 0x32

Home Task # 1


31

Load R16 with value from address 55H and R20

with value 0x23. Add these values and send to

Port D with address 0x32.

Home Assignment Task

Complete all “Review Questions” in the book related

to the topics covered for AVR Architecture and

Assembly Language


32

Assignments

Write Lectures in your own words

Include any example and exercise performed during

lecture

Include couple of more exercises/questions related to

the topics in class. (Be creative – You will get bonus

Marks for it)

Send notes of both lectures by Saturday Night


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Lecture Summary

Hardvard vs von Neumann Architecture

Microcontroller vs Microprocessor

AVR Microcontroller Architecture

General Purpose Registers

The AVR Data Memory

Instructions with Data Memory


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