Why can't I tweak the internal oscillator on a 12C671/JW part? I'm using the standard header file with MPLAB and a PicStart Plus. My code is: org 0x00 movlw 0xXX movwf OSCCAL But no matter what I put in for XX, the osc freq doesn't change. I must be overlooking something pretty basic. I don't really understand what section 8.2.5 of the 12C67X spec sheet says about using a CALL statement when programming OTPs, either. None of the code I've seen written for this part does it that way. Reg Neale