OK Im getting confused again. Ive been working with internal OSC for awhile, and i have done just a basic 4mhz resonator, and a 20mhz ttl osc. however I would like to get to understand more how the OSC's are chosen and used, for instance, say you have a 18F4550, it has a usb option and reading a bit on the notes the usb needs to run at 48mhz for full speed use. now do you have to use a 48mhz crystal or ttl or can you use say a 12mhz and use a div/4 option??? I havent messed with the pll or div stuff, I need to get an explanation of how you get multiple frequencys by changing options on the chip, and does the cpu of the chip still run at the actual crystal freq. ??? can you run a 4550 chip faster than 48mhz?
Someone point me in the right direction, oh and what would be the normal advantage of going with a higher freq crystal ?
Someone point me in the right direction, oh and what would be the normal advantage of going with a higher freq crystal ?