电子信息类专业英语（西电第二版）Unit 9 Digital Signal Processing.ppt

　　Choosing a DSP for a particular application is not always easy. The first decision is on whether to choose a fixed point or a floating point device.［2］ Generally, fixed point devices are cheaper and quicker, but floating point devices are more convenient to program and more suited to calculation-intensive algorithms. Second, the data width of the DSP determines how accurately it can represent numbers. Speed is another issue, not only how many cycles occur in each second, but also how many instructions execute in each cycle and how much work each of these instructions accomplishes. One way to assess the minimum requirements for the DSP is to estimate how many instructions must be executed for each received sample. When this number is multiplied by the sampling frequency, the minimum required number of instructions per second is obtained.　 　　The specific hardware and software features offered by a particular DSP can make one choice better than another, as can the amount of on-chip memory available. Sometimes DSPs are chosen because well-matched supporting hardware, particularly A/D and D/A converters, is obtainable. Frequently, the quality and convenience of the software tools, for both low level and high level programming languages, are also major factors, as is the availability of third party software. As always, cost is a factor. In fact, quite often, the DSP that is fastest and offers the most features, but also fits the budget, is the one selected. 　　DSPs can be purchased in three forms, as a core, as a processor, and as a board level product. In DSP, the term “core” refers to the section of the processor where the key tasks are carried out, including the data registers, multiplier, ALU, address generator, and program sequencer. A complete processor requires combining the core with memory and interfaces to the outside world. While the core and these peripheral sections are designed separately, they will be fabricated on the same piece of silicon, making the