Ενσωµατωµένα Υπολογιστικά Συστήµατα (Embedded Computer Systems) Μάθηµα 1 ηµήτρης Λιούπης
Περιγραφή Μαθήµατος Το µάθηµα εξετάζει την από κοινού ολοκλήρωση υλικού και λογισµικού σε συµπαγή συστήµατα ελέγχου, συ-σχεδίαση υλικού/λογισµικού (h/w s/w codesign) πανταχού παρούσας υπολογιστικής ισχύος (ubiquitous computing). systems on chip internet enabled controllers
Ηύλη του µαθήµατος Ενσωµατωµένα Συστήµατα Υλικού Αρχιτεκτονική σύγχρονων µικροελεγκτών systems on chip Ανίχνευση παραµέτρων περιβάλλοντος και έλεγχος λειτουργιών (sense & control) Αυτοµατισµοί Ροµποτική ίκτυα Ελέγχου Βιοµηχανικά ίκτυα χρήση TCP/IP για εφαρµογές ελέγχου Ad-hoc networks Συστήµατα χαµηλής ισχύος Ενσωµατωµένα πολυµέσα video/audio streaming set top boxes Συ-σχεδίαση υλικού/λογισµικού Ιδιαιτερότητες λογισµικού για ενσωµατωµένα συστήµατα Αυτόµατα καταστάσεων περιγραφή λειτουργιών ελέγχου σε λογισµικό Η έννοια του πραγµατικού χρόνου χρονοδροµολόγηση διεργασιών λειτουργικά συστήµατα πραγµατικού χρόνου Περιφερειακά υλοποιηµένα σε λογισµικό
Σκοπός Μαθήµατος Κατανόηση σχεδιασµού και λειτουργίας των embedded systems, σε επίπεδο Hardware Software System Architecture Παρακολούθηση των τάσεων στην εξέλιξη των embedded systems
Τι είναι ενα Embedded System?
Τι είναι ενα Embedded System? Ενα computing system ενσωµατωµένο σε µια συσκευή. Ένα σύστηµα που περιέχει µικροϋπολογιστή γενικής χρήσης και έχει σχεδιαστεί για ένα µοναδικό σκοπό. ύσκολο να οριστεί. Σχεδόν κάθε υπολογιστικό σύστηµα που δεν είναι desktop computer
Τι είναι ενα Embedded System? ισ, µονάδων παράγονται ανά χρόνο έναντι εκατ. PC Περίπου 50 ανά σπίτι ή αυτοκίνητο Συχνά χρησιµοποιούνται για να: Παρέχουν έλεγχο του χρήστη σε ένα προϊόν Παρακολουθούν ή να ελέγχουν κάτι στον πραγµατικό κόσµο (π.χ. analog)
Κοινά Computer Systems. PC s PDA s Laptops Mainframes Servers
Embedded Systems είναι παντού. Anti-lock brakes Auto-focus cameras Automatic teller machines Automatic toll systems Automatic transmission Avionic systems Battery chargers Camcorders Cell phones Cell-phone base stations Cordless phones Cruise control Curbside check-in systems Digital cameras Disk drives Electronic card readers Electronic instruments Electronic toys/games Factory control Fax machines Fingerprint identifiers Home security systems Life-support systems Medical testing systems Modems MPEG decoders Network cards Network switches/routers On-board navigation Pagers Photocopiers Point-of-sale systems Portable video games Printers Satellite phones Scanners Smart ovens/dishwashers Speech recognizers Stereo systems Teleconferencing systems Televisions Temperature controllers Theft tracking systems TV set-top boxes VCR s, DVD players Video game consoles Video phones Washers and dryers
Χαρακτηριστικά των Embedded Systems Βασίζονται σε κάποιο Processor Λειτουργικότητα ειδική για κάθε εφαρµογή Ειδικευµένα για µία εφαρµογή ή τάξη εφαρµογών ιάδραση (Interact) µε το περιβάλλον τους
Χαρακτηριστικά των Embedded Systems Στενοί σχεδιαστικοί περιορισµοί Power, Size, Timing, Cost to manufacture Στενοί οικονοµικοί περιορισµοί Low design costs, faster time to market, flexible product lines Not User Programmable Stable / Reliable / Correct
Λειτουργία Real-time Περιορισµένος χρόνος απόκρισης (deadline). Hard Real-time Missing deadlines causes a failure Eg. Aircraft navigation system, ABS Soft Real-time Missing deadlines causes degraded performance Eg. Network routers, cell phones Multi-rate Different operations have different priorities & deadlines εν είναι όλα τα embedded systems, real-time systems
Γιατί χρησιµοποιούµε processors? Ευκολία σχεδιασµού. Area & Cost Efficient : Can use the same logic for multiple functions or tasks. ιαθεσιµότητα εργαλείων σχεδιασµού. Αναβαθµιζόµενα (Upgradeable) Κώδικας επαναχρησιµοποιήσιµος (reuseable). Φθηνά!
Γιατί χρησιµοποιούµε processors? Εναλλακτικές: Custom Silicon Very expensive NRE Very long design cycle Complex design Pure Hardware Design Design seldom re-useable Debugging may require board re-spin. Longer design cycle FPGA Complex Design Expensive parts Design seldom reuseable High performance is not often required
Σχεδιασµός Embedded System
Σχεδιασµός Embedded System Σχεδιαστικός κύκλος Requirements Specification Architecture Implementation System Integration Verification Hand-off to Manufacturing
Σχεδιαστικός κύκλος: Requirements Τι θα κάνει το σύστηµα, (what needs it meets, what features it will include). Αναπτύσσονται µε διαφορετικούς τρόπους : µιλώντας µε τους πελάτες µιλώντας στους υπεύθυνους marketing δίνοντας πρωτότυπα στους χρήστες για σχόλια Συχνά ονοµάζεται feature sheet of requirements document
Σχεδιαστικός κύκλος : Functional Requirements What will it do What won t it do Performance Flexibility Testability Upgrade-ability Power Size Unit Cost (Cost to manufacture) Reliability Correctness
Non-functional Requirements NRE (Non Recurring Engineering) cost Cost to design Time to prototype Time to Market Maintainability
Σχεδιαστικός κύκλος: Specification Περιγραφή του τι θα κάνει το σύστηµα. Ο users / customers θα παραλάβει κάποιο µέρος αυτής της περιγραφής, Περιλαµβάνει πως αλληλεπιδρά ο χρήστης µε το σύστηµα. Eg: User interface, power consumption, response times. Tο feature list συχνά περιλαµβάνεται σαν το πρώτο µέρος του specification.
Σχεδιαστικός κύκλος : Architecture Description Λεπτοµερής εξήγηση του how the system will work. The users / customers usually do not get this information. Includes data flow descriptions, block diagrams, etc. Eg. Software tasks, interfaces to components, etc. Specification δεν πρέπει να καθορίζει µια architecture. Tο specification και το architecture παρόµοια. Συχνά, το System Specification και Architecture description είναι µέρη του ίδιου κειµένου.
Σχεδιαστικός κύκλος: Implementation Capture the schematic, write the software, write the RTL. Writing the software, doing the schematic & PCB layout, writing and verifying the RTL, etc. This is what most people associate with design. Different components may be done by different people or teams. Each person or team unit tests his or her own design. Caution: It is very tempting, and very common, for designers to implement a system, and then document it. This commonly leads to design problem because of the system not being well thought out. Eg. Doesn t meet power & response requirements, code size is too big, etc.
Top Down vs. Bottom Up Top down Begin at the most abstract layer, and design successively detailed components until the design is complete. Bottom up Begin with small components and put them together to build up the system. Real System design mixes both You can t do a proper abstract design if you don t know what the components are going to be, and you can t design proper components if you don t know how the system will be put together,
Σχεδιαστικός κύκλος : System Integration Συνδυάζουµεταδιάφοραµέρη του συστήµατος. Όλες οι σχεδιαστικές οµάδες συνεργάζονται για να δουλέψει το τελικό σύστηµα. Συχνά χρειάζεται αναφορά στο implementation. Απαιτείται αρκετός έλεγχος για να επιβεβαιωθεί η σωστή λειτουργία του προϊόντος.
Σχεδιαστικός κύκλος : Verification Making sure the product meets the requirements & specification. Verification Team The people verifying the design should be different from the designers, and preferably, should not be too familiar with the architecture. The designer knows the system intimately; it is natural for him or her to avoid errors, or to simply not see them. Verification Hand-off This should not be done in parallel with integration. Instead there should be a formal hand-off from the system integration team to the verification team. If the design fails verification and has to return to a previous stage, the design needs to be re-verified to prevent new bugs from being introduced.
Σχεδιαστικός κύκλος : Hand-off to Manufacturing The designer has finished the design, and it is time for it to be produced in numbers, and sold. Hand-off documents consist of: Bill of Materials Assembly Instructions Troubleshooting information Test plan / test checklist
Embedded System Design: Case Study
System Design Case Study Digital Camera Anti-lock brakes Cruise Control VCR Controller Microwave
Requirements Functionality Performance Size Cost Testability Upgradeability Reliability NRE Time to Market
Specification Inputs Outputs Operations Interfaces Development Tools Cost breakdown
Architecture Processor Hardware Components Software Components Software Processes
Implementation Capture Schematic Write & compile code
System Integration Ολοκλήρωση των τµηµάτων σε ένα πλήρες σύστηµα
Verification Meet all requirements? Does it do what it s supposed to? Does it meet stability / reliability requirements?
Microprocessor Technology
Computer System Architecture Input Device Processor Output Device Processing Subsystems Memory
Busses Processor Memory Address Bus Data Bus Output Device Input Device Processing Subsystems
Input Devices Keyboard Mouse Button Touch Sensors / Touch Pad Microphone Camera Scanner Communications Receiver Voltage Sensor
Output Devices Display (Monitor, LCD Display) LED Motor Speaker / Sound Card Printer Voltage output Communications Transmitter
Peripheral Subsystems Math coprocessor DSP Coprocessor Timer Subsystem Watchdog
Memory Volatile Memory Cache RAM Non-volatile Memory ROM EEPROM, Flash Mass Storage Hard drive Compact Flash CD / DVD
Address Decoding & Chip selects A[13:0] A[1:0] UART Processor CS1 CS2 CS0 Memory A[12:0] A[7:0] Display A[15:0]
Processor Heart of the system where the intelligence and decision making lies. Processor Characteristics: Architecture (Harvard vs. Von Neumann) Instruction Set (CISC, RISC, VLIW) Pipelining Programmer s Model (accumulator based, general purpose registers, stack based)
Instruction Execution 2 Basic Functions: Move data from one location to another Perform data transformation Steps 1. IF: Fetch the next instruction from memory pointed to by PC. Increment PC. 2. ID: Decode the instruction. 3. EX: Instruction Execution or Address Calculation 4. MEM: Data Memory Access 5. WB: Write Back
Instruction Execution Not all instructions require all stages. Eg. Jump instructions don t read or write memory. Different instructions can take a different number of clock cycles to complete.
Pipelining The different instruction execution steps are (mostly) independent. Different steps can be done in parallel. Non-Pipelined Execution: Inst 1 IF ID EX MEM WB Inst 2 IF ID EX MEM WB t inst t inst
Pipelining Pipelined Execution: Inst 1 IF ID EX MEM WB Inst 2 IF ID EX MEM WB Inst 3 IF ID EX MEM WB Inst 4 IF ID EX MEM WB Inst 5 IF ID EX MEM WB Inst 6 IF ID EX MEM WB t inst t inst
Von Neumann Architecture Processor Output Device Input Device Processing Subsystems Memory
Von Neumann Architecture The architecture used for all general purpose computers. Characteristics: Single Read-write memory space for data & instructions The memory is addressable by location, and the addressing scheme is not affected by the contents.
Harvard Architecture Instruction Memory Processor Output Device Input Device Data Memory
Harvard Architecture Separate Instruction & Data Memories Individual busses for each I/O is mapped into the Data Memory Space More efficient Avoids the memory bus bandwidth problem
Instruction Set CISC Complex Instruction Set Computer Many different instructions, different addressing modes. Eg: Can read operations from memory, perform an operation, and write back to memory with one operation. Can take many clock cycles per instruction.
Instruction Set RISC Reduced Instruction Set Computer Very few instructions, only. Eg: Load from memory is one instruction, do an operation is a second operation, and write back to memory is a third operation. Usually only one clock cycle per instruction. Can support higher clock frequencies.
Microprocessors vs. Microcontrollers Microprocessor Used in general-purpose systems Optimized for performance Does just the processing No on-chip peripherals Minimal On-chip memories Eg. Pentium
Microprocessors vs. Microcontrollers Microcontroller Used in special-purpose systems Optimized for cost On-chip peripherals & I/O components Includes on-chip RAM, ROM, etc. Motorola 68HC11
Microprocessors vs. Microcontrollers