USB in PIC16Xxx and PIC18Xxx

I want to make an adquisition board and send data to PC via USB port, I found the PIC16 and PIC18F have usb ports, and that I can easily programming it in picbasic pro, I saw the usb samples provided by picbasic, but I dont understand well, how is the process to initialize the communication with the pc and one instruction called "ServiceUSBInt" in assembler, if any one know about it, please give me some advice.

Thank you.

Greetings, I myself am still deciding, I currently use several 16f8xx, and was just looking today at the 18fxxxx series. I read some interesting problems upgrading from 16f to 18f.
All I'd like to do is send data to a USB memory stick to be evaluated at a later time.
Perhaps we can deside this together with the help of the forum...

Thanks...

http://www.jianpingusa.com/jpmodule.aspx

http://www.compsys1.com/html/usb_host_kit.html