详细说明：c51的usb的通信程序库，支持51兼容的单片机和pdusbd12接口芯片

文件列表:
  usb_softpack
  ............\demo程序及开发板
  ............\................\D12 USB固件编程.pdf
  ............\................\d12smart_users_manual.pdf
  ............\................\Isr.c
  ............\................\isr.h
  ............\................\Isr.LST
  ............\................\Isr.OBJ
  ............\................\Mainloop.c
  ............\................\MAINLOOP.H
  ............\................\Mainloop.LST
  ............\................\Mainloop.OBJ
  ............\................\USB51S.LIB
  ............\................\USBDEMO
  ............\................\usbdemo.ddk
  ............\................\usbdemo.edk
  ............\................\USBDEMO.M51
  ............\................\usbdemo.mpf
  ............\................\usbdemo.Opt
  ............\................\usbdemo.Uv2
  ............\................\usb_i2c
  ............\................\usb_i2c.hex
  ............\................\usb_i2c.lnp
  ............\................\usb_i2c.M51
  ............\................\usb_i2c.plg
  ............\................\致USB用户的公开信.pdf
  ............\USB_lib
  ............\.......\Isr.c
  ............\.......\isr.h
  ............\.......\USB51S.LIB
  ............\.......\usb51s.txt