PIC16F1946 Datasheet, PDF (71/440 Pages) Microchip Technology – 64-Pin Flash-Based, 8-Bit CMOS Microcontrollers with LCD Driver and nanoWatt XLP Technology

5.4.2
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<3:0>
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 5-8:
TWO-SPEED START-UP
INTOSC
TOST
OSC1 0 1 1022 1023
OSC2
Program Counter PC - N
PC
System Clock
PIC16F/LF1946/47
5.4.3
CHECKING TWO-SPEED CLOCK
STATUS
Checking the state of the OSTS bit of the OSCSTAT
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 1, or the
internal oscillator.
PC + 1
 2010 Microchip Technology Inc.
Preliminary
DS41414A-page 69