PIC16F887I-PT Datasheet, PDF (74/338 Pages) Microchip Technology – 28/40/44-Pin Flash-Based, 8-Bit CMOS Microcontrollers

PIC16F882/883/884/886/887
4.7.2
TWO-SPEED START-UP
SEQUENCE
1. Wake-up from Power-on Reset or Sleep.
2. Instructions begin execution by the internal
oscillator at the frequency set in the IRCF<2:0>
bits of the OSCCON register.
3. OST enabled to count 1024 clock cycles.
4. OST timed out, wait for falling edge of the
internal oscillator.
5. OSTS is set.
6. System clock held low until the next falling edge
of new clock (LP, XT or HS mode).
7. System clock is switched to external clock
source.
FIGURE 4-7:
TWO-SPEED START-UP
HFINTOSC
TOST
OSC1 0 1 1022 1023
OSC2
Program Counter PC - N
PC
System Clock
4.7.3
CHECKING TWO-SPEED CLOCK
STATUS
Checking the state of the OSTS bit of the OSCCON
register will confirm if the microcontroller is running
from the external clock source, as defined by the
FOSC<2:0> bits in the Configuration Word Register 1
(CONFIG1), or the internal oscillator.
PC + 1
DS41291G-page 74
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