Design of Frequency Measuring Module Based on PC104 and CPLD

According to the need of some test system,a high-accuracy frequency measuring module is designed based on PC104 and CPLD.A method of synchronous multi-period frequency measurement is used to achieve the equal precision measure to the tested frequency channel.The hardware circuit of the frequency measuring module is designed.And the detailed VHDL source code to achieve digital frequency using CPLD is given.The interface logic of PC104 bus is compiled using the way of schematic diagram,and the emulation is done by the software of MAXPLUSⅡ.The digital frequency and the interface logic are accurately working showed by the result.This frequency measuring module has been proved to be high-accurate,stable and reliable in the practical application.