Introduction to embedded system and overview of PIC18F452 microcontroller. part2
Introduction to embedded system and overview of
PIC18F452 microcontroller.
Embedded System:
A
computer based system designed to perform one or more dedicated functions.
OR
A device
that include computer (hardware and software) but it is not itself a general
purpose computer, which may expected to perform function without human
interaction.
ü
Responds
monitor and control external environment
using sensors and actuators
ü
May
also contain user interface(create interaction between user and system)
Examples of Embedded System:
Cell
phone, Mp3 player, digital watch and household applications
Automobile E.S:
ü
High
end automobiles may have 100 of microcontrollers
ü
Tension
in seatbelts
ü
Display
services in dashboards
ü
EFI
etc
Characteristics
of
E.S:
ü
Must
be efficient in energy and low manufacturing cost
ü
Must
meet real time constraints
ü
Frequently
connected to environment through sensors and actuators
ü
Must
be hybrid system i.e digital and analogue
ü
Must
be reactive
ü
Sophisticated
functionality
ü
Safe
in operation
Comparison:
Embedded system:
ü
Few
application that are known before design
ü
Mostly
not programmable by end user
ü
Additional
computing power is not useful
General purpose computing:
ü Broad Class of application.
ü Programmable by users
ü Faster is better.
PIC microcontroller:
ü
Stands
for peripheral interface controller
ü
High
performance RISC machine.
ü
Linear
program memory 32K byte
ü
Linear
data memory 1.5 k byte
ü
Speed
upto 10 MIPs
ü
16
bit wide instruction, 8 bit wide data path
ü
Priority
levels for interrupts
Peripheral features:
ü
High
current sink/source 25 mA
ü
Three
external interrupt pins
ü
Timer
0 module: 8 bit/16 bit timer/counter
ü
Timer
1 module: 8 bit timer/counter
ü
Timer
2 module: 16 bit timer/counter
MSSP(Master synchronous series ports) module:
Two
modes of operation
ü
3
wire SPI
ü
I2C
Master and Slave
ü
USART
Module supports RS 485 RS 232
Analogue Features:
ü
Compatible
10 bit analog to digital converter module with
ü
Fast
sampling rate
ü
Conversion
available during sleep
ü
Programmable
low voltage detection
ü
Support
interrupts on low voltage detection
ü
Programmable
Brown out reset
Special Features:
ü
100,000
erase/write cycle enhanced flash program memory
ü
1000,000
erase/write cycle data EEPROM
ü
Flash/Data
EEPROM retention > 40 years
ü
Self
programmable under software control
ü
Power
on reset, power up timer Oscillator Start up timer
ü
Watch
dog timer with its on chip oscillator
ü
Power
saving sleep mode
ü
Single
supply 5 v in circuit serial programming Via Two Pins
ü
In
circuit debug
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