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针对传统的单片机系统数据存储和传输的不便之处,以考勤机为例,设计了一种在原来的考勤机系统中增加一片USB总线接口芯片CH375进行USB通信的方案,实现了考勤机与U盘/PC机之间的数据通信,既方便管理部门利用U盘来完成考勤数据的便捷存取,特别适用于数据量大,采集周期长的环境,又能实现考勤机系统通过USB数据线完成与PC机交换数据的功能。介绍了考勤机系统和CH375的硬件接口电路及其工作原理,给出了CH375作为主机以及从设备时的工作原理、主从模式切换以及软件流程。
In view of the inconvenience of data storage and transmission of the traditional single chip microcomputer system, taking a time and attendance machine as an example, a scheme of adding a USB bus interface chip CH375 for USB communication in the original time and attendance system was designed. Data communication between the disc / PC is convenient for administrative departments to use U disk to facilitate the easy access of attendance data, especially suitable for environments with large amount of data and long acquisition period, and also can complete the time attendance system through the USB data cable Function to exchange data with PC. The hardware interface circuit and its working principle of the attendance system and CH375 are introduced, and the working principle, master - slave mode switching and software flow of CH375 as master and slave are given.