Class1: Introduction to Embedded Systems

Embedded System(ES): Any device that includes a computer(computing device in genral) but is not itself a general purpose computer
-> Hardware & Software part of some larger system are expected to function without human intervention.
->Respond , Monitor & Control external environment using sensors and actuators .
Eg: PDA,printer,Cell phones etc

Characteristic of an ES:
1)Sophisticated features (functionality) 
2)Real time Operation (Not always)
3)Low Manufacturing Cost
4)Application dependent processor (Not General purpose)
5)Restricted memory
6)Low power 
      Power consumption is critical in battery powered devices. Excessive power consumption increases system cost even in wall powered devices.

Manufacturing Cost:
1)Manufacturing cost has different components
       ->Non rec-curing engineering cost for design & development
       ->Cost of production and marketing each unit
2)Best technology choice will depend on number of units we plan to produce

Real time operation:
->Must finish operations by deadlines
       * Hard Real time: Missing deadline cause failure
       * Soft Real time :  Missing deadline results in degraded performance
Many system are multi-rate: must handle operations at widely varying rates

Application dependent requirements:
1)Fault tolerance:Continue operation despite hardware or software faults
2)Safe:System to avoid physical or economic damage to person or property
3)Dedicated system:
   *Predefined functionality:accordingly hardware and software designed
   * Re programing rarely  done during lifetime of the system
   * real time,fault tolerance ,safe

Types of ES:
 1.Similar to general computing
     Eg: PDA,video games,set top boxes,Automatic Teller Machine(ATM)
 2.Control System
     Eg:Feedback control of real time system,vehicle engines,nuclear reactor
 3.Signal processing
    Eg:radar,Sonar,DVD player
 4.Communication & Networking
    Eg:Cellular phones,Internet application

Nature of system functions:
1.Control law
2.Sequencing logic
3.Signal processing
4.Application specific interfacing
5.Fault response (what happens when fault happen,graceful degradation)

Architecture

Memory: software is inbuilt to control system
ADC & DAC: i) provides interface to sensor & actuator respectively
                        ii) receives input from sensor & activate actuator
FPGA:

Data segment in C

Data segment in C is broadly classified in 4 sections: ".txt" , ".rodata" , ".bss" , ".data"

.rodata:The .rodata is also used for storing string constants and read only data's.

.data:The compiler places initialized and uninitialized global variables in the .data section.
.bss: A separate section called .bss is used for uninitialized variables or temporary variable in stack
.txt: Opcode i.e executable code is stored in this section.

Note:Flash content cannot be modified, it can only be erased and re-written hence code and constants are stored in flash while variables are stored in RAM.