State any eight design metrics of embedded system.
1 Answer
  1. Processing Power: Selection of processor is based on the amount of processing power to get the job done and also on the basis of register width required.

  2. Throughput or Performance : the execution time or throughput of the system. Instruction execution time in the system measures performance. Smaller execution time means higher performance. For eg. in mobile phone, voice signals are processed between antenna and speaker in 0.1s shows phone performance. The system may need to handle a lot of data in a short time.

  3. Response: The system has to react to the changing events quickly.

  4. Memory: Hardware design must make the best estimate of the memory requirement and must make the provision for expansion.

  5. Power consumption: Systems generally work on battery and design of both software and hardware must take care of power saving techniques.

  6. Number of units: The number of units expected to be produced and sold will dictate the trade-off between production cost and development cost.

  7. Expected life-time: Design decisions like selection of components to system development cost will depend upon on how long the system is expected to run.

  8. Program Installation: Installation of software on to the embedded system needs special development tools.

  9. Testability and Debug ability: Setting up test conditions and equipment will be difficult and determining what is wrong with the software will become a difficult task without a keyboard and usual display.

  10. Reliability: It is always required that the system designed must give the output for which it is designed.

  11. Power Dissipation: For battery operated system this is important feature. Examples are mobile phone or digital camera where if power dissipation is small battery needs to be recharge less frequently.

  12. Unit cost: the monetary cost of manufacturing each copy of the system, excluding NRE cost.

  13. NRE cost (Non-Recurring Engineering cost): The monetary cost of designing the system. Once the system is designed, any number of units can be manufactured without incurring any additional design cost (hence the term “nonrecurring”).

  14. Size: the physical space required by the system, often measured in bytes for software, and gates or transistors for hardware.

  15. Flexibility: the ability to change the functionality of the system without incurring heavy NRE cost. Software is typically considered very flexible. Flexibility in design enables, without significant engineering cost, development of different versions or product or to develop advanced version later on. For example software enhancement by adding extra functions.

  16. Maintainability: Deals with support and maintenance to the end user or client in case of technical issues and product failure. A more reliable system means with less maintainability. As reliability of the system increases chances of failure and non-functioning also reduces.

  17. Time-to-market: The amount of time required to design and manufacture the system to the point the system can be sold to customers. The main contributors are design time, manufacturing time and testing time. There may be multiple players in the embedded industry who develop products of the same category (like mobile phones, portable media players etc.). If you come with new product and time to market is high competitor may take advantage of it with their product.

  18. Time-to-prototype: The amount of time to build a working version of the system, which may be bigger or more expensive than the final system implementation, but can be used to verify the system’s usefulness and correctness and to refine the system's functionality. If the prototype is developed faster, the actual estimated development time can be bought down.

  19. Correctness: our confidence that we have implemented the system’s functionality correctly. We can check the functionality throughout the process of designing the system, and we can insert test circuitry to check that manufacturing was correct.

  20. Safety: the probability that the system will not cause harm. It deals with possible damages that can happen to the operators, public and the environment due to breakdown of embedded system, or due to the emission of radioactive or hazardous materials from embedded products. Safety analysis is a must in product engineering to evaluate the anticipated damages and determine best course of action.

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