PIC18F2420/2520/4420/4520
REGISTER 23-1: CONFIG1H: CONFIGURATION REGISTER 1 HIGH (BYTE ADDRESS 300001h)
R/P-0
IESO
R/P-0
U-0
—
U-0
—
R/P-0
R/P-1
R/P-1
R/P-1
FCMEN
FOSC3
FOSC2
FOSC1
FOSC0
bit 7
bit 0
Legend:
R = Readable bit
P = Programmable bit
U = Unimplemented bit, read as ‘0’
-n = Value when device is unprogrammed
u = Unchanged from programmed state
bit 7
bit 6
IESO: Internal/External Oscillator Switchover bit
1= Oscillator Switchover mode enabled
0= Oscillator Switchover mode disabled
FCMEN: Fail-Safe Clock Monitor Enable bit
1= Fail-Safe Clock Monitor enabled
0= Fail-Safe Clock Monitor disabled
bit 5-4
bit 3-0
Unimplemented: Read as ‘0’
FOSC<3:0>: Oscillator Selection bits
11xx= External RC oscillator, CLKO function on RA6
101x= External RC oscillator, CLKO function on RA6
1001= Internal oscillator block, CLKO function on RA6; port function on RA7
1000= Internal oscillator block, port function on RA6 and RA7
0111= External RC oscillator, port function on RA6
0110= HS oscillator, PLL enabled (Clock Frequency = 4 x FOSC1)
0101= EC oscillator, port function on RA6
0100= EC oscillator, CLKO function on RA6
0011= External RC oscillator, CLKO function on RA6
0010= HS oscillator
0001= XT oscillator
0000= LP oscillator
DS39631E-page 250
© 2008 Microchip Technology Inc.
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