Introduction to Microcontroller

Introduction
to
Microcontroller

www.pantechsolutions.net
1

What is Microcontroller?
• In simple term – Microcontroller is a small computer that is capable of
performing specific task(s)
– e.g car alarm, washing machine, handphone, PDA…

• There are many similar names
– Microprocessor-based system, controller, MCU, MPU, CPU…

• They can be grouped into two classification
 MCU - Micro Controller Unit
 MPU - Micro Processor Unit

• In general, these microcontroller are the brain of the embedded system

2

MCU and MPU
Classification MCU MPU
Chip Embedded A CPU core, memory, Contain only the main processor (CPU
peripherals, IO … into a single chip. core)

Block Diagram of a MCU
system
Memory Memory IO

CPU Core Peripheral MPU Peripheral

IO

General Application - Self contained to complete a task. -Need external memory, peripheral to
Area - Targeted for small, compact, and accomplish a task
low cost system - Targeted for complex, high
performance and expandable system
Processor (CPU) Core 4, 8, 16 bit 32 bit or above
Examples 8051,pic16f887a,M16, H8, SH1/2 SH3/4,8085
Application Washing machine, car side mirror, Handphone, PDA
air con

3

Components within MCU
Clock -sub Processor Core

i. Processor core Clock -main RAM

ii. Clock ROM PWM

iii. Low power mode
iv. Memory(ROM/RAM) Timer PWM

v. Input/Output Port Timer Timer

vi. Timer / Counter/ WDT Serial

vii. PWM
Timer

Port
Interface

viii. ADC/DAC Timer WDT

ix. Serial Interface ADC LCD

x. On chip Debug
xi. Bus Controller Example of H8/38024

xii. Other
4

i. Processor core
• Function
– Fetch and execute machine code from memory
– Efficiency & Effectiveness are determine by its architecture
• Architecture Type
– Word Size: 4, 8, 16, 32 Bit
– Contains ALU (Arithmetic Logic Unit) for decision process
– Contains General Registers for temporary storage and data manipulation
– Contains Special Registers (PC, Condition, Stack) to assist in program control
– Instruction Sets
– RISC /CISC
– Running Frequency / Voltage
• Possible Measurement
– MIPS (Million Instruction Per Instruction)
• Number of machine instructions that a computer can execute in one second
• Provide only a rough indication for comparison

5

ii. Clock OSC1 OSC2

• MCU needs a clock input to operate
• It can have two clock sources
– A. Main processor clock input
• This clock may be divided or multiply to allow the processor to
run at a slower speed (lower power consumption) or higher
speed
– B. Sub clock input
• 32.768KHz is the usual clock used as this allow accurate
generation of a second via a 16 bit counter.
• These clocks are normally fed via a crystal and two
capacitors to the MCU.

6

iii. Low power mode
• Low Power is achieved via various mean
– Running at slower speed, such as sub
clock(32.768KHz)
• Sleep mode, sub-active, standby…
– Shutting off unused peripherals
• Module stop mode…

Standby mode consume only 1uA

7

iv. Memory (ROM/RAM)
• ROM (Read Only Memory)
– For program and fixed data storage
– Size: as low as 1 KByte to as high as 512 KByte
– Example
1. Masked ROM
2. Flash
3. PROM - Programmable Read-Only Memory
1. OTP - One-Time Programmable

• RAM (Random Access Memory)
– For data storage
– Size: as low as 256 Byte to as high as 4 KByte
– Example
1. SRAM

8

v. Input / Output Port
• Basic interface to control (output) and
monitor (Input) external events.
– High current port
• (20mA), so as to drive LED directly.
– Open-collector/drain port
• Interface to higher supply circuitry
• Wired-Nor condition

9

vi. Timer / Counter / WDT
• Timer (8 or 16 bit) are used to generate or measure
timing for events.
– External event trigger the count
– Compare match to perform a task
– …
• WDT (WatchDog Timer)
– Every time before the counter reach the predefined value, the working
MCU will clear the counter.
– Thus, if the counter is not clear within the specified timing, the WDT
will reset the whole MCU as this signify that the MCU has run wild.

10

vii. PWM
• PWM (Pulse Width Modulation)
– Generate continue pulse of preset duty cycle
• This can be used to drive motor.

11

viii. ADC/DAC
• ADC (Analog-to-Digital Conversion)
– The basic peripheral to interface to the real analog world.
– Characteristic
• Accuracy is determine by number of bits (10,12,14…)
• Sampling frequency
• Conversion technology ( Resistive ladder, Sigma delta…)
Analog Digital
– AVCC, Data -> and eachTransducer input pins
AVSS
Real World
analog ADC CPU
Temperature
Pressure
Sound…

• DAC (Digital-to-Analog Conversion)
– This operate in another way. It output the signal in analog form to the
outside world
12

ix. Serial Interface
• There are different serial interfaces
– Asynchronous mode (2400 BaudRate…)
– Synchronous mode (at higher transfer rate)
– USB, I2C, SPI, CAN…(different communication standard)
• Use for:
– Communication with other devices, such as external RF
module, PC…
• Generally used only 3 pins
– Serial In, Serial Out, and Clock

13

x. On Chip Debug
• Circuitry Incorporated for development and
debugging purposes

• Usually few pins are required for the PC to control
the MCU, via a “JTAG-like” emulator
– Mode pin
– Data In/Out
– Clock pin PC
USB I/F

Target Board

14

xi. Bus Controller
• In the higher performance MCU, a bus controller is
incorporated to manage internal and external
memory bus.

• The external bus may be split into different areas, so
that each area can be assigned with different setting
– Refresh controller for DRAM
– Longer wait cycles for slower devices

15

xii. Other
• There are many possible peripherals that can be
integrated into each MCU, to perform specific tasks,
such as:
– LCD controller
– PLC
– Ethernet MAC
• Other components are:
– Interrupts
– LVD (Low Voltage Detection)
– POR (Power On Reset)

16

MCU Connection
Flashing
Supply via battery or wall plug
/Debugging
(Optional)

VCC

Clock Output Control Motor, LED,
Mode MCU
Reset Input Monitor Temperature, Switches…

GND

17

Choosing MCU
1. Reliability - good
2. Performance – speed, number of bits, architectures
3. Power consumption - low
4. Peripherals – require
5. Number of I/O pins - enough
6. ROM/RAM size – enough
7. Package and Size – manufacturing ease
8. Development Tool – available and ease of Use
9. Roadmap – for next expansion
10. Cost - low
11. Availability – short lead time
12. Support – technical team, application notes…

18

For more Tutorials
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5/24/2011 9:38:29
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Introduction to Microcontroller

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