3 - Case Studies

Abstract

This chapter presents case studies in the generation of sinewaves and their memory map and hardware layout design. At the bottom of the computer size scale comes the microprocessor where the user finds a need for both hardware and software knowledge. For the software support, the development of which inevitably tends to lag behind the hardware is very much in its infancy. Most users at present are working in a low-level language, assembly code, and contend manually with such problems as matching the hardware with the software for input-output assignments, memory addressing, etc. In a case study, a system that outputs a sinewave with the frequency variable, in steps up to 200 Hz, but with fixed amplitude was required. The system was to generate a sinewave by regular outputs of discrete samples along the time course; two possibilities are either a look-up table where a block of memory contains equally spaced samples or a routine that calculates the waveform values as they are required. In the next stage of the development, the hardware requirements are identified and matched with the software when producing the assembly and machine codes. However, there are many limitations of this sinewave generator design when considering a practical instrument, such as accuracy, low-pass filter requirement, and frequency not continuously variable. The comparative lack of software support for microprocessors makes the translation from the algorithm into assembly or machine code a rather tedious job.