Datasheet
PICkitâ„¢ 3 Debug Express Lessons
© 2009 Microchip Technology Inc. DS41370C-page 55
3.9.2 Configuring the Internal Oscillator
The internal oscillator block is selected as the primary oscillator in the Configuration
bits. The OSC bits in the CONFIG1H Configuration Word are set to either INTIO67 or
INTIO7. When INTIO67 is selected, the internal oscillator is the primary oscillator with
the external oscillator pins OSC2 and OSC1 available as RA6 and RA7 IO. OSC =
INTIO7 differs only in that RA6 is not available; instead the internal instruction clock is
output as CLKO on that pin.
The two Special Function Registers that control the internal oscillator block in software
are OSCCON and OSCTUNE, shown in figures 3-44 and 3-45.
FIGURE 3-46: OSCCON: OSCILLATOR CONTROL REGISTER
The IDLEN bit in OSCCON affects how the oscillator behaves in power managed
modes, and is not discussed further here.
The IRFCx bits determine the internal oscillator frequency. These are the outputs of the
postscaler. As Note 2 in Figure 3-44 indicates, the 31 kHz clock can be selected as
either a postscaled version of the INTOSC 8 MHz oscillator, on which all other
frequencies are based, or the INTRC low-power 31 kHz oscillator as discussed in
Section 3.9.1. This selection is made with the INTSRC bit in the OSCTUNE register.