基于EPM240和MSP430的等精度频率计

为提高信号频率的测量精度，设计了基于EPM240和MSP430的等精度频率计，包括恒温晶振、等精度计数单元和频率计算显示单元。该等精度频率计以CPLD（Complex Programmable Logic Device)芯片EPM240T100C5和单片机MSP430F149为核心，YM1602为液晶显示模块，单片机启动CPLD完成等精度计数后读取计数值进行频率计算并显示。理论计算及实际测试结果表明，该频率计的量程为0.5 Hz～10 MHz,全程测量相对误差小于2×10^-8，满足项目中的测频要求。

Equal Precision Frequency Meter Based on EPM240 and MSP430

In order to improve the accuracy of frequency measurement, an equal precision frequency meter based on EPM240 and MSP430 was designed. It includes constant temperature crystal oscillator, equal precision count- ing module, frequency calculation and display module. The CPLD （Complex Programmable Logic Device） chip EPM240T100C5 and MCU （Micro Controller Unit） chip MSP430F149 is the core of frequency meter, YM1602 is the display module. The theory calculation and conclusion of experiment shows that the range of frequency meter is 0.5 Hz - 10 MHz;relative error is always below 2 × 10-8 ;it meets the demand of frequency measurement in the project.