Universal Serial Bus Mass Storage Class<br>UFI Command Specification<br><br>A UFI Device is a removable-media mass storage subsystem, which connects to a Host computer via its<br>Universal Serial Bus (USB) port. The Host and UFI Device communicate by exchanging Command Blocks,<br>data, and status inform
ation as defined by this specification. The method used to transport this information over<br>the USB is defined by the Bulk-Only or CBI transport specifications.<br>A conceptual view of the Host and UFI Device is shown in Figure 1. The UFI device is represented by a USB<br>Floppy Disk Unit (USB FDU). The UFI device driver software running on the Host controls the UFI device by<br>sending it UFI command blocks defined by this specification. The UFI Function in the device processes these<br>command blocks as specified herein.<br>All exchanges of command block, data, and status information are carried out by the transfer of packets over the<br>USB. This exchange is managed by the USB Driver on the Host, and the USB Logical Device process in the<br>USB-FDU.