M序列发生器函数，使用m文件实现，2至7级寄存器，主要分为两个部分。第一部分主要负责输入，输出，第二部分是M序列发生函数-M sequence generator function, 2-7 registers, divided into two parts. The first part is mainly responsible for the input, output, and the second part is the sequence generating function M