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1. What are Embedded Systems? Where they are found useful?
Embedded systems, as the name suggests are smart device technologies built into larger devices. The embedded device is not a computer but can perform the assigned task of computing or data manipulation etc.
We find embedded systems in most of the daily appliances. If we look into TVs, Washing machines or even heating ovens, we find some piece of embedded systems at someplace. So this technology has become part of our life.
2. What are the difference between Embedded Systems (ES) and PC (computer)
Embedded systems differ from a normal PC in several ways. Even though the ES is capable of computation and other jobs done by PC, it is not a complete PC. It may not have a key board, a monitor or even for that matter a processor. We do have an ES with all these, but not a must. PCs are usually applicable to build general-purpose software and most of the applications we build are reusable. In case of ES, most of the development might start from scratch. The ES might be specific to some application and components used in them might be home made. But the latest ES technology enables one to use general-purpose hardware and components, which can re used. The OS of the Embedded systems might not be complete, but only the basic functionalities of OS are taken in a real time environment.
3. What are the parts of Embedded Systems?
An Embedded system is mainly comprised of:
- Real time Operating system (RTOS)
- Serial port, n/w port, i/o peripheral port
- Sensors and actuators
- Mechanical parts.
4. What are the characteristics of Embedded Systems?
- Applications using ES must be reliable, safe and secure
- High efficiency
- Mostly fixed set of application systems
- Frequently reading, processing and controlling physical quantities
- Must react after guaranteed time limit
- Most of the functionalities of the ES are implemented in software
5. What does the software in Embedded System do?
- Respond to external events
- Cope with unusual conditions without human interference
- Carry out multiple jobs at a time
- Replace some of the hardware components.
6. What are the languages used for building the software in ES?
Usually C/C++ are preferred.
Other languages such as Embedded C++ (EC++), Embedded java etc. are also being used.
7. Why C is preferred?
- Processor independence
- High degree of hardware control
- Compilers and cross compilers are available for many processors
8. What are the common micro processors used for ES?
- Zilog Z8 family
- Intel 8051
- X86 family
- Motorola 68k family
- Power PC family
9. What is RTOS?
RTOS stands for Real Time Operating System. It is a compact OS with all the essential features of PC operating system. It is the most suited Operating system for Embedded systems. It is the scale down version of the real time OS.
10. What are the debuggers used in testing Embedded systems?
Many tools are used for debugging and testing embedded systems. A few of them are:-
- Remote debugger: for monitoring and debugging the state of the embedded system software
- In Circuit Simulator: for monitoring and controlling the state of the processor in the embedded systems
- Simulators: used before the design of the Embedded systems and are used to simulate the functioning of the ES on the host machine.
- Logic analyzer: used to check the logical level of the various components of the ES
- Oscilloscopes: to checking the analog signal and also for hardware debugging.
11. What is the required skill sets to work on ES?
- Intel Processors & Controllers
- Micro controllers
- DSP Processors
- C++, C
- ADA (Aerospace)
- Hardware design & testing
12. What are hardwired systems?
They are special category of Embedded systems. They do not need a processor. In these systems, hardware and software are placed separately with an integrated circuitry. Here the circuit is isolated from the device. They are relatively difficult to implement.
13. What are the various layers of the architecture of an Embedded System?
An embedded system has the following layers:
- Hardware layer
- Ready-made packet of hardware such as switches, co-processors, encryption handlers, address matchers, network processors etc.
- Can be bought and used for a device.
- They are application specific standard products (ASSP)
- Real time Operating system
- Two types : Home grown and Standard solutions
- Common ground embedded software
- IP : commonly used for communicating
- Software to forward IP packets of data, accept IP packets of data, send receive data, switching/routing, DNS resolution etc.
- Front end based on consumer intensive agronomy
- Deals with external design of device
- Uses user-friendly interfaces.
14. What are the standard specifications of the various types of Embedded Systems?
Distributed Control system:-
- Moderately inexpensive, mid range design:
- 1-10 MIPS, 1-16 MB RAM ---- times several CPUs per system
- Mid range 16- and 32 bit CISC distributed processors
- A few real time I/O control loops for each CPU
- Low speed networking among CPUs and among systems
- Mission critical system
- Non redundant hardware, ordinary software development
- Electromechanical safeties provide failure protection
- Moderate development costs ($1 Million to $10 Million)
- Hundreds to thousands of systems sold
- 25-50 years life time
- Real life systems:
- High rise elevators
- Large building air handling
- Public transit system
Mission critical system:-
- High reliability, high end design:
- 10 to 100 MIPS, 16 to 32 MB RAM
- Mid to high range 32 bit CISC uni processor
- Analog I/O channels with real time control loops, 10 Mb/sec
- Mission critical system
- Dual redundant hardware
- Painstaking software development and certification
- High development costs( $ 10 Million to $ 50 Million)
- Hundreds of units sold
- 20 to 30 year life time
- Real time system:
- Jet engine control
- Manned spacecraft control
- Nuclear power plant control
- Inexpensive low-end design:
- 100 Kilo-IPS, 1 to 10 Kilo bits memory
- Single chip 8-bit micro controller is only digital IC
- One real time loop for CPU
- Not considered mission critical, but indirectly affects safety
- Bare minimum hardware, small hand coded assembly software
- No redundancy, is expected not to break within life time
- Low development cost ($ 100 K to $ 1 Million)
- Millions of units sold
- 10 to 15 year lifetime
- Real time system:
- Automotive auxiliary components
- Consumer electronics
- Kitchen appliances
- Home automation
- Smart I/O for distributed control system