Datasheet
2010-2012 Microchip Technology Inc. DS41412F-page 357
PIC18(L)F2X/4XK22
24.2 Register Definitions: Configuration Word
REGISTER 24-1: CONFIG1H: CONFIGURATION REGISTER 1 HIGH
R/P-0 R/P-0 R/P-1 R/P-0 R/P-0 R/P-1 R/P-0 R/P-1
IESO FCMEN PRICLKEN PLLCFG FOSC<3:0>
bit 7 bit 0
Legend:
R = Readable bit P = Programmable bit U = Unimplemented bit, read as ‘0’
-n = Value when device is unprogrammed x = Bit is unknown
bit 7 IESO
(1)
: Internal/External Oscillator Switchover bit
1 = Oscillator Switchover mode enabled
0 = Oscillator Switchover mode disabled
bit 6 FCMEN
(1)
: Fail-Safe Clock Monitor Enable bit
1 = Fail-Safe Clock Monitor enabled
0 = Fail-Safe Clock Monitor disabled
bit 5 PRICLKEN: Primary Clock Enable bit
1 = Primary Clock is always enabled
0 = Primary Clock can be disabled by software
bit 4 PLLCFG: 4 x PLL Enable bit
1 = 4 x PLL always enabled, Oscillator multiplied by 4
0 = 4 x PLL is under software control, PLLEN (OSCTUNE<6>)
bit 3-0 FOSC<3:0>: Oscillator Selection bits
1111 = External RC oscillator, CLKOUT function on RA6
1110 = External RC oscillator, CLKOUT function on RA6
1101 = EC oscillator (low power, <
500 kHz)
1100 = EC oscillator, CLKOUT function on OSC2 (low power, <
500 kHz)
1011 = EC oscillator (medium power, 500 kHz-16 MHz)
1010 = EC oscillator, CLKOUT function on OSC2 (medium power, 500 kHz-16 MHz)
1001 = Internal oscillator block, CLKOUT function on OSC2
1000 = Internal oscillator block
0111 = External RC oscillator
0110 = External RC oscillator, CLKOUT function on OSC2
0101 = EC oscillator (high power, >16 MHz)
0100 = EC oscillator, CLKOUT function on OSC2 (high power, >16 MHz)
0011= HS oscillator (medium power, 4 MHz-16 MHz)
0010= HS oscillator (high power, >16 MHz)
0001= XT oscillator
0000= LP oscillator
Note 1: When FOSC<3:0> is configured for HS, XT, or LP oscillator and FCMEN bit is set, then the IESO bit
should also be set to prevent a false failed clock indication and to enable automatic clock switch over from
the internal oscillator block to the external oscillator when the OST times out.