The Design Of Vhdl-based Multi-functional Digital Frequency Meter

Digital cymometer is one of the important measurement tools in latter-day electronic technology field and meanwhile the measurement instrument widely used in many other fields.Digital cymometer is to log the pulse number at stated norm time and convert to frequency which displays in digital form.The reach paper mainly discusses the testing process of using CPLD to measure frequency,period,pulse width and empty ratio.It contains two parts:hardware and software.Hardware circuit contains power supply,key control,display module,SCM and CPLD main control module.Key control module has 5 function keys and 3 time selection keys.A 4×4 little keyboard completes the key value input.Display module uses the crystal vision of YUXIN company.CPLD chip adopts popular VHDL language,the successful preparation of the design process,and in MAX+PLUSⅡsoftware environment;The signal chip computer is written by assembly language which could accurately controls unlock and closure of account strobe.The system combines the control flexibility of SCM with programmable performance of CPLD,so not only can it shorten the period of the development and research,but also has the advantage of compact structure,little volume,high reliability,wide scope and high precision.