Quote Originally Posted by Kamikaze47 View Post
- USB interrupt that just does a USBSERVICE
That's a bit of a tough one. I've heard anywhere from 10ms all the way up to 250ms (I don't believe that one for a second, or 4 service interrupts )

- INT0 interrupt hooked to the clock line of a PS2 keyboard
Only takes a split uSec to handle this one, if all you do is read and store, then return.

- TMR0 interrupt that triggers every 6mS to scan a grid of buttons.
Could probably extend this out a bit, or maybe put the work off to a 2nd PIC talking serial to the 1st PIC.

This almost sounds like a game controller, like for a flight sim...

Also, as you read the I2C doc's, keep in mind that the PIC controls everything about the I2C when in master mode. The device being talked to only does something after the PIC makes it do it. Therefore, if the PIC starts something, and then has to wait for a bit to continue doing something, the device will just sit there and happily hang out and wait for it.