Francesco Stefanni A Design & Verification Methodology for Networked Embedded Systems Ph.D. Thesis April 7, 2011 Università degli Studi di Verona Dipartimento di Informatica Advisor: Prof. Franco Fummi Co-Advisor: Assistant Professor Davide Quaglia Series N◦: TD-04-11 Università di Verona Dipartimento di Informatica Strada le Grazie 15, 37134 Verona Italy Γνωθι˜ σǫαυτoν,´ ǫνˇ o´ιδα oτιˇ oυδ´ ǫν` o´ιδα. Abstract Nowadays, Networked Embedded Systems (NES’s) are a pervasive technology. Their use ranges from communication, to home automation, to safety critical fields. Their increas- ing complexity requires new methodologies for efficient design and verification phases. This work presents a generic design flow for NES’s, supported by the implementation of tools for its application. The design flow exploits the SystemC language, and consid- ers the network as a design space dimension. Some extensions to the base methodology have been performed to consider the presence of a middleware as well as dependabil- ity requirements. Translation tools have been implemented to allow the adoption of the proposed methodology with designs written in other HDL’s. Contents 1 Introduction ................................................... ..... 1 1.1 Thesisstructure ................................. ................ 5 2 Background ................................................... ..... 7 2.1 Networked Embedded Systems . ............ 7 2.1.1 Communicationprotocols ........................ .......... 8 2.2 SystemLevelDesign ............................... ............. 9 2.2.1 Top-downdesignflow ............................. ........ 10 2.2.2 Hardware Description Languages . .......... 11 2.2.3 Abstract Middleware Environment . .......... 12 2.3 Assessing embedded systems correctness. ............... 13 2.3.1 Fault Injection and Fault Simulation . ........... 14 3 Proposed design & verification methodology ........................... 15 3.1 Methodologyoverview............................. .............. 15 3.2 Example of design flow adoption . ............ 18 4 Communication Aware Specification and Synthesis Environment ......... 21 4.1 RelatedWork..................................... .............. 22 4.2 Designflowfornetworksynthesis.................... .............. 23 4.2.1 High-level system specification languages . ........... 24 4.3 Theformalnetworkmodel........................... ............. 25 4.3.1 Tasks ......................................... .......... 27 4.3.2 DataFlows ..................................... ......... 27 4.3.3 Nodes......................................... .......... 28 4.3.4 AbstractChannels .............................. .......... 28 4.3.5 Zones......................................... .......... 29 4.3.6 Contiguities.................................. ............ 30 4.3.7 Graphrepresentation ........................... ........... 31 4.3.8 Relationships between entities . ............ 31 4.4 Networksynthesis................................ ............... 32 4.4.1 Problemformulation ............................ .......... 32 4.4.2 Network synthesis methodology . .......... 33 VI Contents 4.4.3 Networksynthesistaxonomy ...................... ......... 33 4.5 CasestudyI:Temperaturecontrol................... ............... 34 4.5.1 Tasks,dataflowsandzones........................ ......... 34 4.5.2 Taskassignment ................................ .......... 37 4.5.3 Nodeassignment ................................ ......... 37 4.5.4 Assignment of abstract channels . ........... 38 4.6 CasestudyII:Matrixmultiplication ................ ................ 39 4.6.1 Networkspecification ........................... .......... 40 4.6.2 Networksynthesis .............................. .......... 40 4.6.3 Resultofthesynthesisprocess ................... ........... 41 4.7 Conclusionsandfuturework ........................ .............. 42 5 Integration of a Middleware in the CASSE methodology ................. 43 5.1 ProposedMethodology............................. .............. 44 5.1.1 Extraction of Requirements from the Application . .......... 46 5.2 BuildingtheMiddlewareLibrary .................... .............. 47 5.2.1 Modeling Middleware Communication Schema . ....... 47 5.2.2 MW Computation & Communication Requirements . ..... 48 5.3 Conclusions ..................................... ............... 49 6 Dependability modeling into CASSE .................................. 51 6.1 ProposedMethodology............................. .............. 52 6.1.1 Modeling of Dependability Issues . .......... 53 6.1.2 DependabilityConstraints ...................... ............ 54 6.1.3 Network Synthesis & Dependability Analysis . ......... 55 6.2 CaseStudy....................................... .............. 55 6.3 Conclusions ..................................... ............... 58 7 Network Fault Model ................................................ 59 7.1 Background ...................................... .............. 61 7.1.1 Faultmodelingandsimulation .................... .......... 61 7.1.2 Representation of network interactions . ............ 61 7.1.3 Single State Transition Fault Model . ........... 63 7.2 Definition of the Network Fault Model . ............. 64 7.2.1 FSAoftheAbstractChannel ....................... ........ 64 7.2.2 Faultinjectionpolicy .......................... ............ 67 7.2.3 Testwithstandardprotocols ..................... ........... 67 7.2.4 The Time-varying Network Fault Model . ........ 69 7.2.5 TNFM fault activation policy . .......... 70 7.2.6 Observability................................. ............ 70 7.3 Thesimulationplatform ........................... ............... 71 7.3.1 Network Fault Simulation Library . .......... 72 7.4 Casestudies..................................... ............... 72 7.4.1 Temperaturemonitoring ......................... .......... 72 7.4.2 Networkedcontrolsystem........................ .......... 74 7.4.3 Testbench qualification for a networked control system.......... 76 7.5 Conclusions ..................................... ............... 76 Contents VII 8 Propagation Analysis Engine ......................................... 79 8.1 Framework....................................... .............. 80 8.2 Openissues ...................................... .............. 80 8.2.1 The functional fault model . .......... 81 8.2.2 Functional fault parallelization . .............. 82 8.2.3 Theparallelsimulationengine ................... ........... 83 8.2.4 The simulation kernel and the simulation language . .......... 84 8.3 Optimizations ................................... ............... 85 8.3.1 Optimized inputs management . ......... 86 8.3.2 Mux computation optimization . .......... 86 8.3.3 Splittingthenetlistlogiccones................. ............. 86 8.3.4 Optimizing the flops computations . .......... 86 8.3.5 Dealingwiththecompiler........................ .......... 87 8.3.6 Thefourvaluelogic............................. .......... 87 8.3.7 Functioninlining .............................. ........... 87 8.4 Experimentalresults ............................. ................ 88 8.5 Concludingremarks ............................... .............. 89 9 HIF Suite ................................................... ....... 91 9.1 RelatedWork..................................... .............. 92 9.2 HIFSuiteOverview................................ .............. 93 9.3 HIFCore-LanguageandAPIs ......................... ............ 95 9.3.1 HIFBasicElements .............................. ......... 95 9.3.2 SystemDescriptionbyusingHIF................... ......... 96 9.3.3 HIF Application Programming Interfaces . .......... 98 9.3.4 HIFSemantics .................................. .........100 9.4 ConversionTools................................. ...............102 9.4.1 The front-end and back-end conversion tools . ..........102 9.4.2 HDLtypes...................................... .........103 9.4.3 HDL cast and type conversion functions . .........104 9.4.4 HDLoperators .................................. .........105 9.4.5 HDLstructuralstatements....................... ...........106 9.4.6 HDLdeclarationsemantics ....................... ..........106 9.5 ConcludingRemarks............................... ..............108 10 SystemC Network Simulation Library .................................109 10.1 Relatedwork .................................... ...............111 10.2 SCNSLarchitecture .............................. ...............113 10.2.1 Maincomponents............................... ..........114 10.3 IssuesinimplementingSCNSL...................... ..............116 10.3.1 Tasksandnodes ................................ ..........116 10.3.2 Transmission validity assessment ............... .............117 10.3.3 SimulationofRTLmodels ........................ .........117 10.3.4 Thenotionofpacket ............................ ..........118 10.3.5 RTL & TLM models coexistence . .......118 10.3.6 Simulationplanning........................... ............118 10.3.7 Implementation of network protocols and channels . ...........119 Contents 1 10.4 Experimentalresults ............................ .................120 10.5 Conclusions .................................... ................121 11 A final case study ................................................... 123 11.1 Casestudydescription ........................... ................123 11.2 SystemViewmodeling............................. ..............123 11.3 Choosingthemiddleware.......................... ...............124