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Embedded Systems (Subject) / Lektion 1 (Lesson)

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  • What is an embedded system? What are its characteristics? Computer systems, which have a dedicated function within a larger mechanical or electrical system. - embedded within a system - based on microcontrollers - dedicated to specific tasks (designed to perform predefined functions) - tighty constrained (tuned for low cost, few components, minimum power, fast enough) - reactive amd real-time (must monitor the environment and react to changes) Embedded systems can be found at avionics, medical imaging, traffic light controllers, white goods...
  • Which major factors have to be considered, when developing embedded systems? Time to market (has to be ready, when the product enters the market -> before market fall) Technology (which technology to use?) Performance Cost  Power consumption (minimum, but enough to not run out) Reliability (no crashes, performance constraints, timing, functional, lifetime) Testability (easy to test, test performance requirments) Availability of tools (extensions, libraries available, CAD Tools)
  • Which factors have to be considered considering reliability in particular? Timing consider deadlines import for real time systems (hard, firm, soft) , has to be fast enough Metrics : Worst-case execution time (WCET), completetion probability Functional consider correctness important for financial and security systems Metrics: mean time between errors  , error probability Lifetime consider longevity important for consumer products and mission critical systems Metrics: mean time between failure (mittlere Betriebsdauer zwischen Ausfällen für reparierbare Einheiten) and crash
  • What is firmware? Software, which is embedded in electronic systems, to for example display embedded systems onto a LCD. It's carried on ROMs or also recently on flash memory (USB). 
  • Which OS are used in embedded systems? Depending on the scale of the systems either none or specialized OS, like QNX, Nucleus or ECOS. Also embedded versions of standard systems (Linux, Windows) are used.
  • How are embedded systems designed? 1) functional modeling of algorithms 2) partioning of problems 3) design software, hardware and SW/HW interface (paralell with models) 4) determine hardware and software architecture 5) low level implemantation (app source code and gate level design) 6) Map software to processor and logic to hardware
  • Which types of developers are necessary for the dev. of embedded systems? architect takes design decisions software devs  frontend (UI), backend (database, network, OS, drivers), QA/QC (testers) hardware devs frontend (micro/macroarchitecture), backend (timing analysis, placement), hardware designers, verification
  • What is an integrated circuit IC? Set of electronic circuits on one small flat piece (chip), mostly out of silicon, instead of discrete components -> multiple transistors on one component (up to a billion) -> mostly used for everyday use today (smartphones)
  • What is EDA? Electronic design automation is the CAD for electronic systems and is used to design ICs for example.EDA are computer programs that automate parts of the design process.
  • What are the steps of EDA/CAD? System specification (specifies behavior of the system) Architectural design (converts into HW Architecutre) Functional design and logic design (convert into logical circuits) Circuit design (convert into translevel description) Physical design (generate actual layout of system (geometry, materials, placement)) Physical verification and signoff (checks specs like weight, check layout) fabrication packaging and testing  chip
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  • What is CMOS? CMOS is a type of semi-conductor fabrication process, basically a type of logic BiCMOS is a combination of CMOS and bipolar technology (technology for producing devices  where electrical conduction depends on the flow of both majority and minority carriers.) BCD is BiCMOS combined with DMOS
  • How can the circuit design (Chips) be implemented? Full Costum  no prefabricated cells or parts but individually adapted ones to fulfill its purpose All or most of the desin processes are handcrafted Tremendous efforts and time  only benefit with extremly high volume but: very high quality circuits Semi-costum  use of prefabricated elements called standard cells (can be a Gatter, RAM, Processor, Flipflop) relies on EDA tools to assemble them cell-based (standard cells/macro cells) or array-based (masked/field-programmable)
  • What is FPGA? Field Programmable Gate Arrays are a type of IC designed to be configured by a customer or a designer after manufacturing – hence the term "field-programmable".
  • What are circuit models? Circuit models are abstract models of ICs, with details of interest only.
  • What is synthesis? A process of generating a more detailed model from a less detailed one. For example the transformation from behavioral view to structural view or physical view to structural view.
  • Which levels of abstracion exist? 1) Architectural level (Highest level, involves top-level part)     Processor level     Register-transfer level 2) Logic level (Gate level abstracion) 3) Geometric level (material, physical stuff)
  • Which of views/perspectives of models exist? 1) Behavioral view 2) Structural view 3) Physical view
  • Levels of behavioral view ? Processor level (description of the algorithms) Register transfer level (functionality of the blocks) Logic level (boolean equations) Transistor level (analog relations)
  • Levels of physical view? What are the physical locations of the components? Processor level Register-transfer level (how are the macro cells placed?) Logic level (cell layout) Transistor level
  • Levels of structural view? Processor level (IP, RAM, OS) Register-transfer level (how are the IPs implemented? How the inputs routed? ) Logic level (Flip Flops) Transistor level (Detailed implementation of the gates)
  • Which levels of synthesis exists? Architectural synthesis Logical synthesis (from boolean implentation of function to gate level) Physical synthesis (from logic level implentation to transistor/physical layout)
  • How does architectural synthesis work? From behavioral view into structural view. 1) What hardware resources cam implement the operations? 2) Schedule the execution of the operations 3) Bind operations of resources Input:     High Level Language Code

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