Virtual Cycle-accurate Hardware and Software Co-simulation Platform for Cellular IoT

Modern embedded development flows often depend on FPGA board usage for pre-ASIC system verification. The purpose of this project is to instead explore the usage of Electronic System Level (ESL) hardware-software co-simulation through the usage of ARM SoC Designer tool to create a virtual prototype of a cellular IoT modem and thereafter compare the benefits of including such a methodology into the early development cycle. The virtual system is completely developed and executed on a host computer, without the requirement of additional hardware. The virtual prototype hardware is based on C++ ARM verified cycle-accurate models generated from RTL hardware descriptions, High-level synthesis (HLS) pre-synthesis SystemC HW accelerator models and behavioural models which implement the ARM Cycle-accurate Simulation Interface (CASI). The micro-controller of the virtual system which is based on an ARM Cortex-M processor, is capable of executing instructions from a memory module. This report documents the virtual prototype implementation and compares both the software performance and cycle-accuracy of various virtual micro-controller configurations to a commercial reference development board. By altering factors such as memory latencies and bus interconnect subsystem arbitration in co-simulations, the software cycle-count performance of the development board was shown possible to reproduce within a 5% error margin, at the cost of approximately 266 times slower execution speed. Furthermore, the validity of two HLS pre-synthesis hardware models is investigated and proven to be functionally accurate within three clock cycles of individual block latency compared to post-synthesis FPGA synthesized implementations. The final virtual prototype system consisted of the micro-controller and two cellular IoT hardware accelerators. The system runs a FreeRTOS 9.0.0 port, executing a multi-threaded program at an average clock cycle simulation frequency of 10.6 kHz.-Designing and simulating embedded computer systems virtually. Cellular internet of things (IoT) is a new technology that will enable the interconnection of everything: from street lights and parking meters to your gas or water meter at home, wireless cellular networks will allow information to be shared between devices. However, in order for these systems to provide any useful data, they need to include a computer chip with a system to manage the communication itself, enabling the connection to a cellular network and the actual transmission and reception of data. Such a chip is called an embedded chip or system. Traditionally, the design and verification of digital embedded systems, that is to say a system which has both hardware and software components, had to be done in two steps. The first step consists of designing all the hardware, testing it, integrating it and producing it physically on silicon in order to verify the intended functionality of all the components. The second step thus consists of taking the hardware that has been developed and designing the software: a program which will have to execute in complete compliance to the hardware that has been previously developed. This poses two main issues: the software engineers cannot begin their work properly until the hardware is finished, which makes the process very long, and the fact that the hardware has been printed on silicon greatly restricts the possibility of doing changes to accommodate late system requirement alterations; which is quite likely for a tailor-made application specific system such as a cellular IoT chip. A currently widespread technology used to mitigate the previously mentioned negative aspects of embedded design, is the employment of field-programmable gate array (FPGA) development boards which often contain a micro-controller (with a processor and some memories), and a gate array connected to it. The FPGA part consists of a lattice of digital logic gates which can be programmed to interconnect and represent the functionality of the hardware being designed. The processor can thus execute software instructions placed on the memories and the hardware being developed can be programmed into the gate array in order to integrate and verify a full hardware and software system. Nevertheless, this boards are expensive and limit the design to the hardware components available commercially in the different off-the-shelf models, e.g. a specific processor which might not be the desired one. Now imagine there is a way to design hardware components such as processors in the traditional way, however once the hardware has been implemented it can be integrated together with software without the need of printing a physical silicon chip specifically for this purpose. That would be extremely convenient and would save lots of time, would it not? Fortunately, this is already possible due to Electronic System Level (ESL) design, which is compilation of techniques that allow to design, simulate and partially verify a digital chip, all within any normal laptop or desktop computer. Moreover, some ESL tools such as the one investigated in this project, allow you to even simulate a program code written specifically for this hardware; this is known as virtual hardware software co-simulation. The reliability of simulation must however be considered when compared to a traditional two-step methodology or FPGA board usage to verify a full system. This is because a virtual hardware simulation can have several degrees of accuracy, depending on the specificity of component models that make up the virtual prototype of the digital system. Therefore, in order to use co-simulation techniques with a high degree of confidence for verification, the highest accuracy degree should be employed if possible to guarantee that what is being simulated will match the reality of a silicon implementation. The clock cycle-accurate level is one of the highest accuracy system simulation methods available, and it consists of representing the digital states of all hardware components such as signals and registers, in a cycle-by-cycle manner. By using the ARM SoC Designer ESL tool, we have co-designed and co-simulated several microcontrollers on a detailed, cycle-accurate level and confirmed its behaviour by comparing it to a physical reference target development board. Finally, a more complex virtual prototype of a cellular IoT system was also simulated, including a micro-controller running a a real-time operating system (RTOS), hardware accelerators and serial data interfacing. Parts of this virtual prototype where compared to an FPGA board to evaluate the pros and cons of incorporating virtual system simulation into the development cycle and to what extent can ESL methods substitute traditional verification techniques. The ease of interchanging hardware, simplicity of development, simulation speed and the level of debug capabilities available when developing in a virtual environment are some of the aspects of ARM SoC Designer discussed in this thesis. A more in depth description of the methodology and results can be found in the report titled "Virtual Cycle-accurate Hardware and Software Co-simulation Platform for Cellular IoT"

Co-Emulation of Scan-Chain Based Designs Utilizing SCE-MI Infrastructure

Simulation times of complex System-on-Chips (SoC) have grown exponentially as designs reach the multi-million ASIC gate range. Verification teams have adopted emulation as a prominent methodology, incorporating high-level testbenches and FPGA/ASIC hardware for system-level testing (SLT). In addition to SLT, emulation enables software teams to incorporate software applications with cycle-accurate hardware early on in the design cycle. The Standard for Co-Emulation Modeling Interface (SCE-MI) developed by the Accelera Initiative, is a widely used communication protocol for emulation which has been accepted by major electronic design automation (EDA) companies. Scan-chain is a design-for-test (DFT) methodology used for testing digital circuits. To allow more controllability and observability of the system, design registers are transformed into scan registers, allowing verification teams to shift in test vectors and observe the behavior of combinatorial logic. As SoC complexity increases, thousands of registers can be used in a design, which makes it difficult to implement full-scan testing. More so, as the complexity of the scan algorithm is dependent on the number of design registers, large SoC scan designs can no longer be verified in RTL simulation unless portioned into smaller sub-blocks. To complete a full scan cycle in RTL simulation for large system-level designs, it may take hours, days, or even weeks depending on the complexity of the circuit. This thesis proposes a methodology to decrease scan-chain verification time utilizing SCE-MI protocol and an FPGA-based emulation platform. A high-level (SystemC) testbench and FPGA synthesizable hardware transactor models are developed for the ISCAS89 S400 benchmark circuit for high-speed communication between the CPU workstation and FPGA emulator. The emulation results are compared to other verification methodologies, and found to be 82% faster than regular RTL simulation. In addition, the emulation runs in the MHz speed range, allowing the incorporation of software applications, drivers, and operating systems, as opposed to the Hz range in RTL simulation

Formal and Informal Methods for Multi-Core Design Space Exploration

We propose a tool-supported methodology for design-space exploration for embedded systems. It provides means to define high-level models of applications and multi-processor architectures and evaluate the performance of different deployment (mapping, scheduling) strategies while taking uncertainty into account. We argue that this extension of the scope of formal verification is important for the viability of the domain.Comment: In Proceedings QAPL 2014, arXiv:1406.156

ERIGrid Holistic Test Description for Validating Cyber-Physical Energy Systems

Smart energy solutions aim to modify and optimise the operation of existing energy infrastructure. Such cyber-physical technology must be mature before deployment to the actual infrastructure, and competitive solutions will have to be compliant to standards still under development. Achieving this technology readiness and harmonisation requires reproducible experiments and appropriately realistic testing environments. Such testbeds for multi-domain cyber-physical experiments are complex in and of themselves. This work addresses a method for the scoping and design of experiments where both testbed and solution each require detailed expertise. This empirical work first revisited present test description approaches, developed a newdescription method for cyber-physical energy systems testing, and matured it by means of user involvement. The new Holistic Test Description (HTD) method facilitates the conception, deconstruction and reproduction of complex experimental designs in the domains of cyber-physical energy systems. This work develops the background and motivation, offers a guideline and examples to the proposed approach, and summarises experience from three years of its application.This work received funding in the European Community’s Horizon 2020 Program (H2020/2014–2020) under project “ERIGrid” (Grant Agreement No. 654113)

An Adaptive Design Methodology for Reduction of Product Development Risk

Embedded systems interaction with environment inherently complicates understanding of requirements and their correct implementation. However, product uncertainty is highest during early stages of development. Design verification is an essential step in the development of any system, especially for Embedded System. This paper introduces a novel adaptive design methodology, which incorporates step-wise prototyping and verification. With each adaptive step product-realization level is enhanced while decreasing the level of product uncertainty, thereby reducing the overall costs. The back-bone of this frame-work is the development of Domain Specific Operational (DOP) Model and the associated Verification Instrumentation for Test and Evaluation, developed based on the DOP model. Together they generate functionally valid test-sequence for carrying out prototype evaluation. With the help of a case study 'Multimode Detection Subsystem' the application of this method is sketched. The design methodologies can be compared by defining and computing a generic performance criterion like Average design-cycle Risk. For the case study, by computing Average design-cycle Risk, it is shown that the adaptive method reduces the product development risk for a small increase in the total design cycle time.Comment: 21 pages, 9 figure