i want to write usb protocol manually using 16f searies micro controller
using assembly language can u help me

 

Welcome to AAC. I moved your post, as it was in an existing thread in the Off Topic area, and would have been ignored. Please do not hijack threads.

The USB protocol is pretty busy - http://www.faculty.iu-bremen.de/birk/lectures/PC101-2003/14usb/FINAL VERSION/usb_protocol.html.

There are PIC's with the USB interface built in.

 

Some PIC18 microcontrollers have USB support built in but I have not heard of anyone bit-bashing USB in a PIC16 chip. I suspect that the PIC16 chip does not have the memory resources or speed to support USB.

 

Well, it can be done. I know someone who've done it before. The only advice I can give you is to get the USB protocol document from the usb.org and study it. Otherwise, using PIC with USB support would be a much easier and less painful route.