So most software can be test on the pc and can be transplanted to gateway after all is ok . the platform is designed from top to bottom , at first , the functionalities and interface of the three module should be specified clearly , and then go into the details of it , came back to modify the interface made before . the tree modules are connected through pci bus . adsl module implements the adsl modern as the atu - r ; the network interface consists of two part , wileless lan ( it is optional ) and lan , can connect with two different lan . the main control module controls the action of the others which is made of sdram , microcontroller , flashrom and serial port 为了设计方便,整个硬件平台按照自顶向下的设计方式,首先按照功能分为三部分: adsl模块,网络接口模块,主控模块,这些模块之间采用流行的pci总线相连接,规定模块之间的接口关系,然后进行细化,反馈回来完善原先定义的接口关系。其中, adsl模块可作为单独的adsl调制解调器使用,起到atu - r的功能:网络模块由两部分组成,无线lan和lan接口(其中前者为可选项) ,可以连接wirelesslan和lan 。主控模块起到协调的作用,包括sdram 、微控制器、 flashrom 、串口等。