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USB protocol and uC ,Help needed

Started by blisca September 21, 2007
Hello,i'm Diego from Milan ,Italy
i did at home a kind of "educational board" with a 9S12 microcontroller and
aPDIUSBD12 USB interface

i'm trying to implement the protocol to make my USB device enumerated

Using this site  http://www.beyondlogic.org/usbnutshell/usb7.htm#Enumeration
as a reference,of course my firmware will be a little different being my
device based on  parallel data instead of I2C
and having a completely different  uController

 i read the steps in the USB Enumeration process.Focus on steps 3 and 4:

3)The MS Windows host asks for the first 64 bytes of the Device Descriptor.
4)After receiving the first 8 bytes of the Device Descriptor, it immediately
issues another bus reset.

something is not clear,my micro is going to transfer on the EP0 buffer 64
bytes,and this should be a continous operation ,

what happens when the USB device encounters a bus reset?it doesn't look like
it is signalled to the uController
so will the other 56 bytes transferred and wasted?or should I implement an
interrupt routine able to stop the not needed transfer?

thank you all.