Quote Originally Posted by sstt1976 View Post
Now I want to burn the chip with an HSPLL setting and maintain the exact same internal timing for all my PBP instructions. I know that HSPLL automatically makes the 18F2550 run internally at 96MHz so I tried a /4(/3) scaler and a DEFINE OSC 48 statement but I can tell it's running slightly different than before.
HSPLL doesn't make it run at 96Mhz internally.
All HSPLL does is take the external (or internal) clock input and multiply it by 4. If you try to run the PIC at 96Mhz internally (i.e. using an external 24Mhz clock with HSPLL turned on), it won't run. The PIC is only spec'd to run at 48Mhz maximum. The HSPLL (assuming you're running an external clock) allows you to use a 12Mhz external clock to run the PIC at 48Mhz (assuming all of your dividers are set correctly). Using a 12Mhz (or lower) external clock is a lot easier to design and a lot less 'fussy' than trying to design around a 48Mhz external oscillator (which would most likely require a lot of shielding, grounding, and so on)...