PIC12F683 Datasheet, PDF (30/148 Pages) Microchip Technology – 8-Pin Flash-Based, 8-Bit CMOS Microcontrollers with nanoWatt Technology

PIC12F683
3.7.2 RESET OR WAKE-UP FROM SLEEP
The FSCM is designed to detect oscillator failure at any
point after the device has exited a Reset or Sleep con-
dition and the Oscillator Start-up Timer (OST) has
expired. If the external clock is EC or RC mode,
monitoring will begin immediately following these
events.
For LP, XT or HS mode the external oscillator may
require a start-up time considerably longer than the
FSCM sample clock time or a false clock failure may be
detected (see Figure 3-9). To prevent this, the internal
oscillator is automatically configured as the system
clock and functions until the external clock is stable (the
OST has timed out). This is identical to Two-Speed
Start-up mode. Once the external oscillator is stable,
the LFINTOSC returns to its role as the FSCM source.
Note:
Due to the wide range of oscillator start-up
times, the Fail-Safe circuit is not active
during oscillator start-up (i.e., after exiting
Reset or Sleep). After an appropriate
amount of time, the user should check the
OSTS bit (OSCCON<3>) to verify the
oscillator start-up and system clock
switchover has successfully completed.
REGISTER 3-2:
bit 7
bit 6-4
bit 3
bit 2
bit 1
bit 0
OSCCON – OSCILLATOR CONTROL REGISTER (ADDRESS: 8Fh)
U-0
R/W-1 R/W-1 R/W-0
R-1
R-0
R-0
—
IRCF2
IRCF1
IRCF0 OSTS⁽¹⁾
HTS
LTS
bit 7
Unimplemented: Read as ‘0’
IRCF<2:0>: Internal Oscillator Frequency Select bits
000 = 31 kHz
001 = 125 kHz
010 = 250 kHz
011 = 500 kHz
100 = 1 MHz
101 = 2 MHz
110 = 4 MHz
111 = 8 MHz
OSTS: Oscillator Start-up Time-out Status bit
1 = Device is running from the external system clock defined by FOSC<2:0>
0 = Device is running from the internal system clock (HFINTOSC or LFINTOSC)
HTS: HFINTOSC (High Frequency – 8 MHz to 125 kHz) Status bit
1 = HFINTOSC is stable
0 = HFINTOSC is not stable
LTS: LFINTOSC (Low Frequency – 31 kHz) Stable bit
1 = LFINTOSC is stable
0 = LFINTOSC is not stable
SCS: System Clock Select bit
1 = Internal oscillator is used for system clock
0 = Clock source defined by FOSC<2:0>
R/W-0
SCS
bit 0
Note 1: Bit resets to ‘0’ with Two-Speed Start-up and LP, XT or HS selected as the oscillator
mode or Fail-Safe mode is enabled.
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
DS41211B-page 28
Preliminary
 2004 Microchip Technology Inc.