摘要： 介绍了一种USB从设备访问主设备的方法。该方法利用USB从设备端存储器中建立的交换缓存区，无须拔插flash存储卡即可实现USB从设备端对主设备端文件的直接访问，从而使USB从设备可访问远大于自身存储空间的文件。通过该方法可实现手持播放器以低成本和省电的方式扩展外接硬盘。

关键词: USB总线, USB从设备, USB主设备, 直接访问, 存储器

Abstract: A file access method from USB device to USB host is introduced. By using switch buffer built in memory of USB device, this method realizes the direct access to the file in USB host from USB device, which makes USB device access much larger external file than its storage capability. This method makes it possible that a portable player extends external harddisk with low cost and power saving.

Key words: USB bus, USB device, USB host, direct access, storage device

中图分类号: 

• TP311.5