PIC16LF1824T39A_12 Datasheet, PDF (57/418 Pages) Microchip Technology – 20-Pin Flash Microcontrollers with XLP Technology

5.2.2.7
Internal Oscillator Clock Switch
Timing
When switching between the HFINTOSC, MFINTOSC
and the LFINTOSC, the new oscillator may already be
shut down to save power (see Figure 5-7). If this is the
case, there is a delay after the IRCF<3:0> bits of the
OSCCON register are modified before the frequency
selection takes place. The OSCSTAT register will
reflect the current active status of the HFINTOSC,
MFINTOSC and LFINTOSC oscillators. The sequence
of a frequency selection is as follows:
1. IRCF<3:0> bits of the OSCCON register are
modified.
2. If the new clock is shut down, a clock start-up
delay is started.
3. Clock switch circuitry waits for a falling edge of
the current clock.
4. The current clock is held low and the clock
switch circuitry waits for a rising edge in the new
clock.
5. The new clock is now active.
6. The OSCSTAT register is updated as required.
7. Clock switch is complete.
See Figure 5-7 for more details.
If the internal oscillator speed is switched between two
clocks of the same source, there is no start-up delay
before the new frequency is selected. Clock switching
time delays are shown in Table 5-1.
Start-up delay specifications are located in the
oscillator tables of Section 31.0 “Electrical
Specifications”.
PIC16LF1824T39A
 2012 Microchip Technology Inc.
Preliminary
DS41657A-page 57