【正文】 ion illustrated by the center of the target. In this simplified example, the yellow cross illustrates a hardware prototype ECU that exceeds the ideals for power consumption and fails to meet the clock speed ideals. Because of the timetomarket constraint, the system architecture continues to be based upon the initial hardware prototype without adequate exploration of alternative choices. The end result of a hardware based development process is a suboptimum product that may miss the design targets. Conversely the green crosses show an alternative path to the optimum design solution. Several virtual systems are assembled and tested in the same timetomarket window. The final virtual system is ontarget for the design parameters, and the resulting work products from the virtual system are quickly converted into the physical product. Models of the system are initially created at a high level of abstraction, and, through the modelbased methodology, are driven to a full virtual implementation, then to an actual product. The modelbased methodology approach proposes the use of an architecture exploration tool to facilitate the rapid exploration of various CPUs, memories, and peripherals (system architecture). The system architecture is shown in the upper right of Figure 2 . The upper left of Figure 2 shows early revisions of the functional models of the system, known as system behavior. The system behavior and system architecture are bined, and an optimal solution is achieved by iteratively paring the performance of each partitioned alternative. The objective is to evaluate the various architectural and partitioning alternatives to gain a first order approximation of the optimum design. Some of the proposed EDA tools for architecture exploration offer the ability to model microcontroller architectures in only a few weeks duration. The simulations for architectural simulation may be only 80% accurate, but that is believed to be good enough to make the first order choices of microcontroller, timer architecture and memory usages. Our evaluations of the architectural exploration tools, however, indicate that the industry has not yet focused on solving microcontroller selection in a general way. As this paper presents, there is a tradeoff between simulation accuracy, cost of the modeling effort, and the time to model a new architecture. We are awaiting further tool maturation before expanding beyond paper evaluations of architecture exploration. The industry trend is toward building libraries of very accurate architecture models that execute the embedded software directly. A sufficient library of these detailed models can then be used to evaluate system architectures and also used for the final software development. We have focused our efforts on the lower left box of Figure 2。與市場同步的制約會把軟件的檢測推向系統(tǒng)的水平，并導(dǎo)致對生產(chǎn)硬件的更大需求在軟件開發(fā)的流程中更早得到滿足。并且，只有硬件原型單元被創(chuàng)建，軟件的應(yīng)用才能得以實(shí)施，這使得軟件的開發(fā)者和系統(tǒng)檢測工作組處于一個很不利的位置。最后的虛擬系統(tǒng)滿足所有的設(shè)計參數(shù)，并很快被轉(zhuǎn)化為實(shí)際產(chǎn)品。隨著其他 模型的制成，這些準(zhǔn)確循環(huán)仿真將能夠解決其他結(jié)構(gòu)探尋空間問題。 仿真速度和準(zhǔn)確性 在我 們討論系統(tǒng)之前，提供一些背景資料非常重要，這些資料說明了模型抽象的層面以及它們自身是如何進(jìn)行最好的應(yīng)用的。其目的是通過評價不同的結(jié)構(gòu)和分隔選項得到最佳設(shè)計的第一個近似方案。因此，通過去除重復(fù)工作