Data processing: structural design – modeling – simulation – and em – Simulating electronic device or electrical system
Reexamination Certificate
1999-10-29
2001-05-08
Teska, Kevin J. (Department: 2763)
Data processing: structural design, modeling, simulation, and em
Simulating electronic device or electrical system
C703S016000, C703S017000, C703S023000, C714S028000
Reexamination Certificate
active
06230114
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to computer hardware simulators, and more specifically, to a system and method for the simulation of an electronic system that includes one or more target processors executing software and interacting with hardware.
BACKGROUND
Computer simulation of digital hardware systems has become a common technique to reduce the cost and time required for the design of such hardware systems. Simulating digital hardware allows a designer to predict the functioning and performance of the hardware prior to fabricating the hardware. As more and more digital systems incorporate a processor, including a microprocessor, a digital signal processor, or other special purpose computer processor, there has been increased effort to develop a simulation system that includes simulating the hardware and simulating the running of software on a processor that is included in the digital system. Having such a simulation system allows a designer to test the operation of software on the processor before a physical processor is available. Thus, for example, a designer may be able to start designing a system incorporating a new microprocessor before the manufacturer actually releases physical samples of the microprocessor. In addition, a system designer designing an integrated circuit or a system on a printed circuit board that includes a processor can, for example, use the simulation system to test the integrated circuit or printed circuit board implementation, including operation of software on the processor part, and any testing interactions between the processor and the other digital circuit elements of the integrated circuit or board, before the integrated circuit or board is fabricated. This clearly can save time and money.
Such a simulation system is called a co-simulation design system, a co-simulation system, or simply a design system herein, and the environment for operating such a co-simulation system is called a design environment. The processor is called a target processor and the computer system on which the environment operates is called the host computer system. The hardware other than the processor is called digital circuitry. The computer software program that is designed by a user to operate on the target processor is called the user program.
The target processor may be a separate microprocessor with the digital circuitry being external to the microprocessor (e.g., on a printed circuit board or elsewhere in the system), or may be a processor embedded in an application specific integrated circuit (ASIC) or a custom integrated circuit (IC) such as a very large scale integrated (VLSI) device, with the digital circuitry including some components that are part of the ASIC or IC, and other components that are external to the ASIC or IC.
A design environment capable of co-simulation requires 1) the capability of accurately simulating the digital circuitry, including timing, and 2) the capability of accurately simulating on the host processor the running of the user program on the target processor, including the accurate timing of operation of the user program and of any software/hardware interaction. The first requirement is available today in a range of hardware description languages (HDLs) such as Verilog and VHDL, and simulation environments using them. It also is available as a set of constructed libraries and classes that allows the modeling of hardware in a higher-level language such as ‘C’ or ‘C++.’ The second requirement is for a processor simulator using an executable processor model that both accurately simulates the execution of a user program on the target processor, and can interact with the digital circuitry simulation environment. Such a processor simulator should provide timing information, particularly at times of software/hardware interaction, i.e., at the software/hardware interface. A processor model that includes such accurate timing information is called a “quantifiable” model herein.
One known way of providing such processor simulation is to simulate the actual hardware design of the processor. This can be done, for example, by specifying a processor model in a hardware description language (HDL). Such a model is called an architectural hardware model herein, and a processor simulator derived therefrom is called a hardware architecture simulator herein. An architectural hardware model clearly can include all the intricacies of the processor design, and thus is capable of accurate timing. Since it is written in a hardware description language, it may be treated as a hardware device in a hardware simulation environment. The main but great disadvantage of simulating the operation of the processor by simulating the hardware in some HDL is the slow execution speed, typically in the range of 0.1-100 instructions per second.
Another known way of accurately simulating the execution of software on a processor for inclusion in a co-simulation environment is an instruction set simulator (ISS), wherein both the function and the sequencing of the microprocessor is mimicked in software. An instruction set simulator still executes relatively slowly, compared for example to how fast a program would execute on the target processor. An ISS executes in the range of 1,000 to 50,000 instructions per second depending on the level of timing and operational detail provided by the model.
Both the ISS and the architectural hardware model approaches to simulating software are relatively slow, and users of such environments often express frustration at their inability to run simulations at practical speeds. HDL and ISS microprocessor models limit the number of software cycles that can be properly verified on a hardware-software modeling system; a few thousand per second is all they allow. On the other hand, real systems execute 50-1000 million instructions per second or more. From this arises a disparity of a factor between about 10,000 to 200,000 in performance, so that 3 to 60 hours of simulation may be needed to model 1 second of real-time target processor performance.
One solution to the slow speed of simulating a processor is to use a hardware processor model. This device includes a physical microprocessor and some circuitry for interfacing and interacting with the design environment simulating the digital circuitry. The memory for the target processor is simulated as part of the digital circuitry. Such an approach is fairly expensive. Another limitation is due to having two definitions of time operating on the same simulation system: simulation time of a hardware simulator, and processor time, which is real time for the hardware processor. Correlating these is difficult.
Another solution is to use an emulator as the target processor model. An emulator, like a hardware processor model, is a hardware device, typically the target processor, and usually includes some memory. The emulator is designed to emulate the operation of the microprocessor. Such a processor emulator when it includes memory can execute the user program directly, but again is expensive and may require the development of external circuitry to interact with the hardware simulator simulating the digital circuitry. U.S. Pat. No. 5,838,948 describes an environment that uses an emulator for speeding up the running of a user program in the design environment.
Thus there still is a need for a design environment that operates on a host computer system which includes a mechanism for rapidly simulating the operation of a target processor.
Behavioral processor simulators are known that can run a user program on the host computer system. With such an approach, the functional outcome of the software execution is combined with the outcome of executing the hardware models described, for example, in an HDL. While such processor models can run at more than 100 million instructions per second and have reasonable functionality, they include no timing or architectural precision, for example to accurately simulate the interaction between the digital circuitry and the processor.
Thus there st
Chan Ricky L. K.
Hellestrand Graham R.
Kam Ming Chi
Torossian James R.
Inventek
Knox Lonnie A.
Rosenfeld Dov
Teska Kevin J.
Vast Systems Technology Corporation
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