我自己写的过零点判断模块，经过调试效果很理想-I wrote it myself to determine zero-crossing module, after testing the effect of very satisfactory

程序实现2FSK的解调，使用过零检测法，分为预处理模块和鉴频处理模块，Verilog语言，在modelsim仿真通过-2FSK Program for demodulation of zero-crossing detection method used, divided into pre-processing module and the discriminator processing module, Verilog language, adopted in the modelsim sim