通信主从机双向系统时钟同步，用于扩频、跳频等。由从机发起时间校准请求，主机回复时间信息，达到主从机的时钟同步。-Slave two-way communication between the host system clock synchronization for spread spectrum, frequency hopping and so on. Initiated by the slave time alignment request, the host response time information to achieve the clock synchronization of master and slave.