The document provides an overview of embedded systems basics. It defines an embedded system as a computer system with built-in hardware and software that performs a dedicated function within a larger mechanical or electrical system. Embedded systems are designed to respond to particular inputs, perform pre-programmed functions, and control physical devices. They are found in devices such as appliances, vehicles, industrial equipment, medical devices, and more. The document outlines the characteristics, components, and applications of embedded systems.

1. Embedded Systems Basics
Dr. N. Mathivanan
Visiting Professor
Department of Instrumentation and Control Engineering
National Institute of Technology
TRICHY, TAMILNADU
INDIA

2. • Embedded System (Embedding a computer)
o That has built-in small computer (not general-purpose)
o Software embedded with it, preprogrammed.
o Not programmable by users and not visible to users
o It is a part of a larger system
o System performing single function, repeatedly.
o Starts by itself and runs independently without human
intervention.
o Responds, monitors, controls external environment
o Uses sensors, actuators and has analog interfacing
o Generally built around microcontroller
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3. • Examples
Household appliance: Oven, DVD Player, Washing machine, Digi Camera
Automobile: Engine, brake, door, climate, stability controls
Computer peripheral controllers: Keyboard, disk drive, LAN
Computer peripheral: Printer, scanner,
Communication and networking device: Router
Building automation: safety, security, utility management systems
Bio-Medical: ECG recorder, Patient monitoring system
Industrial systems: Robotics, CNC machine controller
Environmental parameters monitoring: Temp., wind speed, RH
Scientific equipments: Spectrum analyzer, Storage oscilloscopes,
Entertainment: TV, Audio/Video equipments
Surveillance systems: Video camera, bio-metric, smart card reader
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4. • Applications
Simple Control: Front panel control of oven, Remote controller, etc.
Image Processing: Decompression, Descrambling in TV set top box
Signal Processing: DVD players
Data Acquisition: data loggers, remote data loggers, transmitters
Network Control: GPIB controller, CAN bus, Ethernet, surveillance
• Camera
Typically 3 microcontrollers are used,
A 32-bit mC provides auto-focus fn.
• Automobile
More than 100 microcontrollers provide ABS, ESC, etc. functions
4-bit mC checks seat belt, 8-bit mC manages dashboard function,
Networked,
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5. Embedded System Classification
• Based on functionality
Stand-alone, Networked, Real-time, Wireless
• Based on performance of microcontroller
Small scale:
Single 8/16-bit, mC/mP, little HW, SW complexity, battery operated
Medium scale:
Single/few 16/32-bit mC/DSP, RISC based, HW, SW complex,
Uses SW development tools – IDE, Simulators, debuggers
Large scale:
Large HW, SW complexity, Networking,
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6. • Embedded System Characteristics:
Low power Consumption*,
High Code Density,
Limited resources (less memory, no hard-disk)
Run time efficiency,
Real-time operation? (not required in all systems),
Sophisticated functionality, Weight, Cost
May have to withstand extreme environmental conditions
(high temperature and humidity)
Choosing right hardware and software platforms a complex task
(based on user application)
• Designer objective:
To find cheapest solution that meets requirements
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7. Typical Embedded System
• Differential drive mobile robot
UART
PWM
ZigBee
Slot Sensor
Transiever
(LPC2129)
GPIO
INT
Slot Sensor
EXT
MICROCONTROLLER
DRIVER
M
M
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8. • Embedded System Hardware
CPU: Processor/Microcontroller/Embedded Processor
Memory: EEPROM, SRAM,
Controllers: Memory, Bus, interrupt & DMA controllers
Peripherals: ADC, DAC, Timer/Counter, PWM, RTC
Communication interfaces: UART, I2C, SPI, USB
Network interfaces: CAN, Ethernet,
Power Control
I/O Mapping: Memory mapped I/O, I/O mapped I/O
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9. Sensors with associated signal conditioners
Actuators with associated drivers
Storage devices:
User interfaces -
Inputs: switches, touch pad, etc.
Outputs: Display devices, indicators
Reset (WDT),
Power supply,
Clock (crystal oscillator),
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10. • Embedded System Software
Operating system:
Provides interface between user and hardware
Manages system resources
Memory, CPU, Device, File management
Controls execution of all kinds of programs
Provides security
Real-Time Operating System
Ensures to finish operations by deadline
Hard Real-Time
missing deadline results in system failure (safety critical)
Soft real-time:
missing deadline results in degraded performance
(playing video)
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11. • Embedded System Software Continued…..
Software Development Tools
IDE, Cross Compilers, Emulators, Simulators
Debug tools
Debugger
Application software
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12. Flash Memory Reprogramming
• In-System Programming (ISP)
Requires running program to be stopped
System set to programming mode
Restarted after reprogramming is completed
• In-Application Programming (IAP)
Target board can be reprogrammed while application is running
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13. System Development Process
Hardware Software
Analyze requirements Develop program codes using tools
Define specifications Download to target system
Design block level architecture Test and Debug
Design component level hardware Repeat the above cycle till test O.K.
Assemble the target system
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14. Microprocessor based system
• Microprocessor, ROM, RAM, I/O ports, shared bus
• Data transfer – between CPU and ROM / RAM / IO ports
• No memory to memory or between memory and I/O transfers
• The above transfer only with DMA controller
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15. Microcontroller Internal Architecture
• Wide range of microcontrollers each targeted for particular appln.
• Computers are designed to have RISC / CISC architecture and Von
Neumann / Harvard architecture.
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16. Reduced Instruction Set Computer - RISC
Type of processor architecture that utilizes highly optimized small set
of instructions.
Characteristics:
• Executes every instruction in one cycle (one cycle/instruction).
• All instructions have fixed length.
• Allows pipelining technology in which instruction fetch, decode
and execute stages to take place simultaneously.
• Generally incorporates large number of registers to reduce
number of memory accesses.
• Uses Load/Store instructions to access memory
• Uses less silicon, pin count, and runs at high clock speed
• Programs are lengthier (occupies more memory)
• Real-time applications N. Mathivanan

17. • Emphasis on software
• Examples: Atmel AVR, PIC, ARM microcontrollers
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18. Primary objective of CISC architecture is to allow the use of less
amount of memory space for a program
Characteristics:
• Emphasis on hardware
• Programs are shorter (high code density) and hence execution
faster
• Very large instruction set, instructions variable length
• Instruction pipelining cannot be implemented easily, (complicated)
• More specialized addressing modes are implemented
• Normally used in PCs, Workstations, Servers
• Examples: Intel x86 variants
Complex Instruction Set Computer - CISC
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19. Von Neumann Architecture
Computer architecture that shares single common bus system
for program and data. (single storage place for storing program,
data)
Characteristics
• Have shared signals and memory for program and data
• Fetches first instruction from program memory and then data from
data memory – slows down the program execution
• Bus width same for code and data
• Design of control unit is simple
• Used in PCs, Workstations, high performance computers
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20. Harvard Architecture
Computer architecture that uses separate signals and
storage for program and data memory
Characteristics
• Allows simultaneous access of program and data
• Usually program memory is read-only and data memory is read-
write
• Width of program and data memory may be different
• Allows pipelining
• Used in embedded computers, digital signal processors
• Design of control unit is complex
• Free data memory cannot be used for instruction and vice-versa
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21. Von Neumann vs. Harvard
CPU
Program
Program
CPU
Decoder
Control
Decoder
VonNeuman Architecture
Data
Addr
Control
Registers
Data
Registers
Addr Addr
Data
Control
Instruction Instruction
Memory Memory
Data Data
Memory
Memory
Harvard Architecture
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22. Microprocessor vs. Microcontroller
Microprocessor
Basic components
ALU, Accumulator, Registers, Control
Unit, Instruction Decoder, Bus
Microcontroller
Basic Components
CPU, ROM, RAM, Peripherals, I/O ports,
Serial interfaces, Controllers, Bus
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23. Microcontrollers
PIC16F84A ARM7-TDMI Based LPC2148
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24. 8051
AT
89S52
68HC11
Atmega
328
PIC
16F84A
PIC
18F452
ARM7-
TDMI-S
LPC2148
ARM
Cortex-M3
LPC1768
CPU 8-bit 8-bit 8-bit 8-bit 8-bit 8-bit
16-bit/
32-bit
16-bit/
32-bit
Data Bus /
Instr bus
8-bit 8-bit 8-bit 8-bit
8-bit /
14-bit
8-bit /
16-bit
32-bit /
32-bit
32-bit /
32-bit
Address bus 16-bit 16-bit 16-bit 16-bit 14-bit 16-bit 32-bit 32-bit
Clock Speed 12 MHz 0–33 MHz 0–4 MHz 20 MHz 20 MHz 0–40 MHz 10–25 MHz 0-100 MHz
Memory
Program
Memory
Int - 4 KB
Extl - 64 KB
8 KB
(flash)
8 KB 32 KB
14-bits
1 KB
32 KB 512 kB 512 kB
Data
Memory
128 B
(64 KB ext)
256 B 256 B 2 KB
RAM - 68B
EEPROM-64B
RAM-1536 B
EEPROM-256B
32 KB +
8 KB
Up to
64 KB
Interrupts 5 8 18 2 4 18 22
DMA
Channels
No No No No No No
One
(for USB)
8 Channel
Gen purpose
I/O ports
4 x 8-bit
32 I/O lines
4 x 8-bit
32 I/O
40 I/O
lines
23/28/32 13
4 x 8-bit
1 x 3-bit
45 pins 70 / 52
Comparing Microcontrollers
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25. Peripherals
8051
AT
89S52
68HC11
Atmega
328
PIC
16F84A
PIC
18F452
ARM7-
TDMI-S
LPC2148
ARM
Cortex-M3
LPC1768
ADC No No
One
8 channel
8-bit
One
8/6 Ch
10-bit
No
One
8 Channel
10-bit
Two
6+8 Chs,
10-bit
One
8 Chs,
12-bit
DAC No No No No No No
One
10-bit
One
10-bit
Timers 2 x 16-bit 3x16-bit
16-bit
3 Cap
5 Comp
2x8-bit,
1x16-bit,
comp, cap
One
8-bit
4
8-bit / 16-
bit
2 x 32-bit each
with 4 Cap/Mat
Chs
4
PWM
Channels
No No
8-bit–4 Ch,
16-bit–2Ch
6 No
Cap/comp
PWM – 2
6 1 + 6
RTC No No No Yes No No Yes Yes
WDT No Yes Yes Yes Yes Yes Yes Yes
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26. Serial Interfaces
8051
AT
89S52
68HC11
Atmega
328
PIC
16F84A
PIC
18F452
ARM7-
TDMI-S
LPC2148
ARM
Cortex-M3
LPC1768
I2C No No No One No
Yes
(MSSP)
Two Three
I2S No No No No No No No One
SPI No No One Yes No
Yes
(MSSP)
One One
SSP No No No No No Master SSP One 2
UART
One
(Full Duplex)
Yes
One
Yes
(SCI)
No No No
2 (one with
modem cont)
4 (one with
modem cont)
USART No No No Yes No Yes No No
USB No No No No No No
One, (Device
compliant)
One (device/
host/ OTG)
Ethernet
Port
No No No No No No No
Ethernet
MAC
CAN No No No No No No 2 Chs 2 ChsN. Mathivanan

27. Other Features
8051
AT
89S52
68HC11
Atmega
328
PIC
16F84A
PIC
18F452
ARM7-
TDMI-S
LPC2148
ARM
Cortex-M3
LPC1768
Power
Saving
Modes
No 2 modes
2 modes,
Wait & stop
6 modes Yes Yes
Yes
Two
Yes
Two
No. of
Pins,
Package
40/44/44
DIP/PLCC/
QFP
40/44/44
DIP/PLCC/
TQFP
48/52
DIP/PLCC
28/32/32p
DIP/MLF/
TQFP
18/18/20
PDIP/SOIC/
SSOP
40/44/44
PDIP/TQFP/
PLCC
64 LQFP
100 LQFP
100 TFBGA
100WLCSP
No. of
Instr.
255 ? 109 131 35 75 ? ?
CISC /
RISC
CISC CISC CISC RISC RISC RISC RISC RISC
Architecture
Von
Neumann
Von
Neumann
Von
Neumann
----
Harvard
(modified)
Harvard
(modified)
Von
Neumann
Harvard
Pipelining ----- ---- ---- ---- 2 stage 2 stage 3 stage 3 stage
Special
Features
----- ---- ----
Multiplier,
Analog
Compar
---- Multiplier
Hardware
Multiplier
Ethernet,
Memory
Management,
QEIN. Mathivanan

28. Review Questions
1. What is an embedded system?
2. Distinguish computer in embedded system from general purpose
computer.
3. List the characteristics of embedded system.
4. Brief any four major fields where embedded systems are used.
5. Compare the characteristics of SRAM and DRAM.
6. What is the function of cache memory?
7. What is interrupt?
8. What is the function of interrupt controller?
9. What is DMA? Explain basic DMA operation.
10. Draw the functional block diagram of a mP based system. Explain
11. Name any four sensors used in embedded applications.
12. What are the basic elements providing analog I/O functions?
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29. 13. List various hardware components used in implementing embedded
system
14. Brief the different types of Software used in embedded
applications / embedded system development
15. Outline the hardware design of any typical embedded system (may
be a mobile robot).
16. What are referred as uni-tasking and muti-tasking?
17. List a few synchronous and asynchronous serial communication
interfaces.
18. Discuss: RISC vs. CISC
19. Discuss: Von Neumann vs. Harvard architectures
20. Distinguish PLC and embedded system
21. Name any one microcontroller for low end, mid range and high end
embedded applications. N. Mathivanan

30. Embedded System Implementation
• Hardware
Processing element:
Microcontroller – Processor, Memory (Flash, RAM, Cache)
Peripherals:
Input & Output devices
Interfacing sensors and actuators
Communication interfaces:
Interfacing protocols
Bus system
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31. • Software
System software:
Operating system, RTOS,
Development tools: Cross compilers, emulators, simulators
Debug tools:
Application software
• Multi-tasking and concurrency
Embedded systems need to deal with several inputs and outputs and
multiple events occurring independently. Separate tasks handle the
situation
Multitasking – OS to allow switching back and forth between tasks.
Concurrency – Appearance of simultaneous execution of tasks.
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