Basics of micro controllers for biginners

ETU 07421:
MICROPROCESSOR
APPLICATIONS
CLASS NOTES

MICROPROCESSOR
Microprocessor
• Is a programmable digital component that in cooperates
the function of CPU on a single semiconducting
integrated circuit.
• Is the integration of number of useful function into a
single IC package that has;
-Ability to execute a stored set of instruction to carry out
user defined task.
- Ability to access the external memory chips to both read
and write data to and from the memory

Functional Block of
Microprocessor

Basic architecture
• Von neumann Architecture.
• Harvard architecture

Von Neumann Architecture.
• The design has a single memory bank for
storing both program and data.
• It has single bus which is multiplexed to be used
as both address bus and data bus.
• The content of RAM can be used for both
variable storage as well as program storage.

Harvard Architecture
• Separate memory banks for program and data
storage.
• It has RAM for data storage and separate ROM
for storing program
• It has two separate address bus for
-Program memory
- Data memory

Comparison
Von Neumann Versus Harvard
Von Neumann Harvard
• Single memory for both
program and data
• Separate memory for
program and data
• Single bus used to access
both data and memory
• Separate buses available to
access program and data
• Instruction parallelism is not
possible
• Instruction parallelism can
be done
• It takes more than one
machine cycle (Fetching and
execution are done)
• It takes only one machine
cycle. Fetching and
execution are done
simultaneous

Advantages of Von Neumann
Architecture
• It simplifies the microcontroller chip design
because only one memory is accessed.
• The content of RAM can be used for both
variable (data) as well as program
(instruction) storage

Advantages of Harvard
Architecture
• The Harvard architecture tends to execute
instruction in fewer instruction cycle than
Von Neumann architecture. This is
because greater amount of parallelism is
possible.

Instruction Set
• CISC- Complex Instruction Set Computer
• RISC- Reduced Instruction Set Computer

Complex Instruction Set
Computer
• Is Microprocessor that understand large number
of complex instruction but it process them
relatively slowly
• Internal instruction involves many individual
execution steps and thus many clock cycles.
• The design is complex, costly and also
instruction set consist of more than 100
instruction

Reduced Instruction Set
Computer
• Is Microprocessor that uses relatively
simple architecture with fewer built in
command.
• Increase in speed.
• Design is relatively simpler, economical
and usually has less than 100 instructions

Comparison
RISC versus RISC
RISC CISC
• Less number of Instruction • More number of Instruction
• All are single cycle instruction • Each instruction take at least 2 or 3
machine cycle.
• Design of architecture is easier and
cheap
• Design of architecture is complex
and costly
• Program length get increased due
to shortage of instructions
• Program length is less because
variety of instructions is available
• Execution speed is faster since most
instruction are single cycled
• Execution speed is low since the
instruction takes many machine
cycles
• Example; PIC series, ARM
processors
• Examples; 8051 families, Pentium

MICROCONTROLLERS
 Is a small (micro) single chip computer designed to
perform a specific function, and the specific function is to
control objects, process or events.
 It is dedicated to one task or set of closely related task. It
is similar to PC(it has similar components but onto a
single chip)
-CPU, memory (ROM and RAM).
-I/O ports, serial ports.
- Timers e.t.c

Functional block of
Microcontroller

Comparison
Microprocessor Versus Microcontroller
Microprocessor Microcontroller
• Memoryhastobeinterfacedexternally • Hasinbuiltprogramanddatamemory
• I/Oportshastobeinterfaced • HasInbuiltdigital/analogueI/Oports
• HasnointernalTimers,serialportsetc • HasTimer,serialportsandotherfeatures
• Highclockrates >3GHz • Slowclockrates(4–20MHz)
• Buswidthverywide • Buswidthverynarrow
• Expensive • Lessexpensive

In Summary
Microprocessor
Is a general purpose chip and is used in multifunction
computer or device with the help of multiple chips to
handle various tasks
Microcontroller
Is a self contained, CPU, RAM, ROM, I/O ports and Timers
on the same chip function independently as a single chip
computer dedicated to specific task to control single
system

Why Microcontroller?
• Task specific.
• Add computer power to the device to enable it to perform
more better at low cost.
• Low cost, small packaging, low power requirements.
• Ideal for application in which low cost, power and space
is crucial.
• Easy integration with other circuits
• Programmable and re-programmable.

Embedded System
• The system to control, monitor or assist the
operation of equipment, machinery or plant.
The term “Embedded” reflect the fact that they are
integral part of the system they control.

Common characteristics of
Embedded Systems
• Specific and single functioned
Execute a single instruction repeatedly
• Optimized for hardware
Compact, low cost, fast, low power.
• Reactive and operated in real time

MICROCONTROLLER BASED
PROJECTS
HOW TO SELECT A SUITABLE
MICROCONTROLLER FOR THE
PROJECT

Step 1: Make a list of required
hardware interfaces

Step 2: Examine the software
architecture
• How heavy or how light the processing requirements will
determine whether you go with an 80 MHz DSP or an 8
MHz 8051
• Are there any high frequency control loops or sensors?
• Estimate how long and how often each task will need to
run
• How much processing power will be needed.
• The amount of computing power required will be one of
the biggest requirements for the architecture and
frequency of the microcontroller.(how fast a machine can
perform an operation).

Step 3: Select the architecture
• Can the application get by with eight bit
architectures? How about 16 bits? Does it
require a 32 bit ARM core?
• Microcontroller selection can be an
iterative process. You may select a 16-bit
part in this step but then in a later step find
that a 32 bit ARM part works better.

Step 4: Identify Memory Needs
• Flash and RAM are two very critical
components of any microcontrollers.
Making sure that you don’t run out of
program space or variable space is
undoubtedly of highest priority.

Step 5: Start searching for
microcontrollers
• One place that can be a good place to
start is with a microcontroller supplier

Step 6: Examine Costs and
Power Constraints
• Examine the power requirements and cost
of the part.
 If the device will be powered from a battery and
mobile, then making sure the parts are low-power
 If it doesn’t meet power requirements then keep weeding
the list down until you have a select few.

Step 7: Check part availability
• Starts checking on how available the part
is.
• What are your requirements for
availability?

Step 8: Select a development kit
• One of the best parts of selecting a new
microcontroller is finding a development kit
to play with and learn the inner working of
the controller.

Step 9: Investigate compilers
and tools
• Examine the compiler and tools that are
available.
 It is important to make sure that all the necessary
tools are available for the part. Without the right tools the
development process could become tedious and
expensive.

Programming Language
The preferred programming language is C
language.

Why C language is preferable
language

Software Architecture
Software architecture that will be used is
Super loop Architecture.

Super loop
• A super loop is a program structure comprised of an
infinite loop, with all the tasks of the system
contained in that loop.
• General pseudo-code for a super-loop
implementation is given as:
Function Main_Function()
{
Initialization();
Do_Forever
{
Check_Status();
Do_Calculations();
Output_Response();
}
}

Why Super-loop is needed
• We have no operating system to return to,
so the application will keep looping until
the system power is removed.
• It help to perform all the tasks of the
system in a reasonable amount of time
• It help task to be performed in good order.

Compiler
• A compiler is a computer program (or set
of programs) that transforms source code
written in a programming language (the
source language) into another computer
language (the target language, often
having a binary form known as object
code).
• The preferred compiler is Mikro C compiler

Why Mikro C is the preferred compiler?
• lots of hardware and software libraries.
• Compiler comes with comprehensive Help
file and lots of ready-to-use examples
designed to get you started in no time.

Characteristics
• RISC CPUs
– 8-bit
– 16-bit
• Number of I/O pins: 4-70
• Memory types and sizes:
– Flash; OTP; ROM
– 0.5k – 256k

Speeds
• All PICs require oscillators to execute
instructions:
– Internal*
(low speeds, up to 8 MHz)
– External (high speeds, up to 40 MHz)
• Instructions are executed at least at ¼
oscillator speed (4 clocks/instruction)
(*
Note: not all PICs have internal oscillators)

A/D converters and C/C modules
• All PICs have between 0 and 16 A/D
converters with 8/10-bit resolution
• 8-16 bit Timers/Counters
• Comparator Modules (0-2)

Example: PIC16F877A
5/6 Programming pins
8 A/D channels
2 Oscillator Inputs
2 RS-232 inputs
33 I/O ports

Basics of micro controllers for biginners

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