PIC16F818/819
FIGURE 4-6:
PIC16F818/819 CLOCK DIAGRAM
PIC18F818/819
CONFIG (FOSC2:FOSC0)
OSC2
OSC1
Sleep
LP, XT, HS, RC, EC
Peripherals
OSCCON<6:4>
Internal Oscillator
8 MHz
4 MHz
111
110
101
CPU
Internal
Oscillator
Block
2 MHz
1 MHz
100
011
010
001
000
500 kHz
250 kHz
125 kHz
31.25 kHz
8 MHz
(INTOSC)
31.25 kHz
Source
31.25 kHz
(INTRC)
WDT
REGISTER 4-2:
OSCCON: OSCILLATOR CONTROL REGISTER (ADDRESS 8Fh)
U-0
—
R/W-0
IRCF2
R/W-0
IRCF1
R/W-0
IRCF0
U-0
—
R-0
U-0
—
U-0
IOFS
—
bit 7
bit 0
bit 7
Unimplemented: Read as ‘0’
bit 6-4
IRCF2:IRCF0: Internal Oscillator Frequency Select bits
111= 8 MHz (8 MHz source drives clock directly)
110= 4 MHz
101= 2 MHz
100= 1 MHz
011= 500 kHz
010= 250 kHz
001= 125 kHz
000= 31.25 kHz (INTRC source drives clock directly)
bit 3
bit 2
Unimplemented: Read as ‘0’
IOFS: INTOSC Frequency Stable bit
1= Frequency is stable
0= Frequency is not stable
bit 1-0
Unimplemented: Read as ‘0’
Legend:
R = Readable bit
-n = Value at POR
W = Writable bit
‘1’ = Bit is set
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared x = Bit is unknown
DS39598E-page 38
2004 Microchip Technology Inc.
MICROCHIP [ MICROCHIP ]
