lect 3 4/19/2025
Introduction to Microcontroller
Why do we need to learn Micro-
processors/controllers?
• The microprocessor is the core of computer
systems.
• Nowadays many communication, digital
entertainment, portable devices, are controlled
by them.
• A designer should know what types of
components he needs, ways to reduce
production costs and product reliable.
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Different aspects of
a micro-processor/controller
• Hardware :Interface to the real world
• Software :order how to deal with inputs
Evolution of Microprocessor-based
Systems
• First came transistors
• Integrated circuits
• SSI (Small-Scale Integration) to ULSI
• Very Large Scale Integration circuits (VLSI)
• 1- Microprocessors (MPU)
• Microcomputers (with CPU being a microprocessor)
• Components: Memory, CPU, Peripherals (I/O)
• Example: Personal computers
• 2- Microcontroller (MCU)
• Microcomputers (with CPU being a microprocessor)
• Many special function peripheral are integrated on a single circuit
• Types: General Purpose or Embedded System (with special functionalities)
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The Computer
• What is a computer?
• A programmable electronic device that can store, retrieve,
and process data.
• A machine that manipulates data according to a list of
instructions.
• Classification of Computers (power and price)
• Personal computers
• Mainframes
• Supercomputers
• Dedicated controllers – Embedded controllers
Personal Computers
• Any general-purpose computer
• intended to be operated directly by an end user
• Range from small microcomputers that work with 4-bit words
to PCs working with 32-bit words or more
• They contain a processor – known by different names:
• Microprocessor – built using Very-Large-Scale Integration
technology; the entire circuit is on a single chip
• Central Processing Unit (CPU)
• Microprocessor Unit (MPU) – similar to CPU
http://en.wikipedia.org/wiki/Personal_computer
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Mainframes
• Massive amounts of memory
• Use large data words…64 bits or more
• Mostly used for military defense and large business
data processing
• Examples: IBM 4381, Honeywell DPS8
Supercomputers
• Fastest and most powerful mainframes
• Contain multiple processors (CPUs)
• Used for scientific applications, and number crunching
• Now have teraflops performance
• FLoating Point Operations Per Second (FLOPS)
• Examples of special-purpose supercomputers:
• Belle, Deep Blue, and Hydra, for playing chess
• Reconfigurable computing machines or parts of machines
• GRAPE, for astrophysics and molecular dynamics
• Deep Crack, for breaking the DES cipher
• MDGRAPE-3, for protein structure computation
http://en.wikipedia.org/wiki/Supercomputer
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Microprocessor-Based Systems
• Central Processing Unit (CPU)
• Memory
• Input/Output (I/O) circuitry
• Buses
– Address bus
– Data bus
– Control bus
Microprocessor based system
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Microprocessor based system
MPU
GP-
CLK Reg
CPU
CPU
Arithmetic
Register
Logic
Arrays
Unit
Control Unit
Microprocessor-Based System with Buses:
Address, Data, and Control Signals
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Microprocessor-based Systems
Microprocessor
• The microprocessor (MPU) is a computing and logic
device that executes binary instructions in a sequence
stored in memory.
• Characteristics:
• General purpose central processor unit (CPU)
• Binary
• Register-based
• Clock-driven
• Programmable
Microprocessor-based Systems
Microprocessor
• Microprocessor is the “brains” of the computer
• its job is to fetch instructions, decode them, and then execute them
• 8/16/32/etc –bit (how it moves the data)
• contains:
ALU performs computing tasks – manipulates the data/ performs numerical and logical
computations
Registers are used for temp. storage
Control unit is used for timing and other controlling functions – contains a program
counter (next instruction’s address and status register)
System software: A group of programs that monitors the functions of the entire system
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Microprocessor-based Systems
Memory
Memory is a group of registers
16 register – address: 0-15 – in binary:
0-1111; Address lines: A0-A3
Serves two major purposes
storing the binary codes for the sequence of
instructions specified by programs (program)
storing binary data that the computer needs
to execute instructions (data)
Microprocessor-based Systems
Memory
Memory Types
• R/W: Read/Write Memory; also called RAM
• It is volatile (losses information as power is removed)
• Write means the processor can store information
• Read means the processor can receive information from the
memory
• Acts like a Blackboard!
• ROM: Read-Only memory;
• It is typically non-volatile (permanent) – can be erasable
• It is similar to a Page from your textbook
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Microprocessor-based Systems
Input/Output (I/O) Ports
The way the computer communicates with the
outside world devices
Peripherals are connected to I/O ports
Peripherals are I/O devices
Input devices
Output devices
Examples
Printers and modems,
keyboard and mouse
scanner
Universal Serial Bus (USB)
Microprocessor-based Systems
Input/Output (I/O) Ports
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Microprocessor-based Systems
System- Buses
• The three components – MPU, memory, and I/O – are connected by a group of
wires called the BUS
• Address bus
consists of 16, 20, 24, or 32 parallel signal lines (wires) - unidirectional
these lines contain the address of the memory location to read or written
• Control bus
• consists of 4 to 10 (or more) parallel signal lines
• CPU sends signals along these lines to memory and to I/O ports
• examples: Memory Read, Memory Write, I/O Read, I/O Write
• Data bus
• consists of 8,16, or 32 parallel signal lines
• bi-directional
• only one device at a time can have its outputs enabled,
• this requires the devices to have three-state output
Address bus
• CPU reads/writes data from the memory by addressing a specific
location; outputs the location of the data on the address buss; memory
uses the address to access the proper data
• Each I/O device (such as monitor, keypad, etc) has a unique address as
well (or a range of addresses); when accessing a I/O device, CPU places
its address on the address bus. Each device will detect if it is its own
address and act accordingly
• Devices always receive data from the CPU; CPU never reads the address
buss (it is never addressed)
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Data bus
• When the CPU reads data from memory, it first outputs the address on the
address bus, then the memory outputs the data onto the data bus; the CPU
reads the data from data bus
• When writing data onto the memory, the CPU outputs first the address on the
address bus, then outputs the data onto the output bus; memory then reads
and stores the data at the proper location
• The process to read/write to a I/O device is similar
Control bus
• Address and data buses consist of n lines, which combine to transmit
one n bit value; control bus is a collection of individual control
signals
• These signals indicate whether the data is to be read into or written
out the CPU, whether the CPU is accessing memory or an IO device,
and whether the I/O device or memory is ready for the data transfer
• This bus is mostly a collection of unidirectional signals
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Expanded Microprocessor-Based System
• Note the directions
of:
• address bus
• Data bus
• Control signals
• What is the width of
the:
• address bus?
• Data bus?
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