Datasheet

 2012 Microchip Technology Inc. DS30575A-page 39
PIC18F97J94 FAMILY
3.2 Oscillator Configuration
The oscillator source (and operating mode) that is used
at a device Power-on Reset (POR) event is selected
using Configuration bit settings. The Oscillator Configu-
ration bit settings are in the Configuration registers
located in the program memory (refer to Section 28.1
“Configuration Bits” for more information). The
Primary Oscillator Configuration bits, POSCMD<1:0>
(CONFIG3L<1:0>), and Oscillator Configuration bits,
FOSC<2:0> (CONFIG2L<2:0>), select the oscillator
source that is used at a POR. The FRC Oscillator with
Postscaler (FRCDIV) is the default (unprogrammed)
selection. The Secondary Oscillator, or one of the inter-
nal oscillators, may be chosen by programming these bit
locations.
The Configuration bits allow users to choose between
11 different clock modes, as shown in Tabl e 3 - 1 .
TABLE 3-1: CONFIGURATION BIT VALUES FOR CLOCK SELECTION
Oscillator Mode Oscillator Source POSCMD<1:0> FOSC<2:0> Notes
Fast RC Oscillator with
Postscaler (FRCDIV)
Internal 11 111 1, 2
Fast RC Oscillator divided by 16
(FRC500kHz)
Internal 11 110 1
Low-Power RC Oscillator (LPRC) Internal 11 101 1
Secondary (Timer1) Oscillator
(SOSC)
Secondary 11 100 1
Primary Oscillator (HS) with PLL
Module (HSPLL)
Primary 10 011
Primary Oscillator (MS) with PLL
Module (MSPLL)
Primary 01 011
Primary Oscillator (EC) with PLL
Module (ECPLL)
Primary 00 011
Primary Oscillator (HS) Primary 10 010
Primary Oscillator (MS) Primary 01 010
Primary Oscillator (EC) Primary 00 010
Fast RC Oscillator with PLL Module
(FRCPLL)
Internal 11 001 1
Fast RC Oscillator (FRC) Internal 11 000 1
Note 1: OSC2 pin function is determined by the CLKOEN Configuration bit.
2: Default oscillator mode for an unprogrammed (erased) device.