请看pic12xxx说明书下面两段: Note 1: Address 0000h becomes the effective reset vector. Location 01FFh (PIC12C508) or location 03FFh (PIC12C509) contains the MOVLW XX INTRC oscillator calibration value.
Location 01FFh (PIC12C508) or location 03FFh (PIC12C509) contains the internal clock oscillator calibration value. This value should never be overwritten.