Re: who can help me about uP
There are some new PICs out, with USB 1.1 Full Speed integrated.
These are the 18F2550 and some of the same series... (both, 28-pin and 40-pin available) Just have a look at the microchip website.
If you don't have access to them, you could use an ftdi232bm or similar rs232-usb-converters to access your pics with your 16F877. If you use an ftdi245bm, you could use the parallel-slave-port to transfer the data to the pic with particular high speed.
If that is not enough, you have to use an 18F, as mentioned above.