PIC16F193X Datasheet, PDF (117/418 Pages) Microchip Technology – 28/40/44-Pin Flash-Based, 8-Bit CMOS Microcontrollers with LCD Driver and nanoWatt Technology

8.5.7 FREQUENCY SELECT BITS (IRCF)
The output of the 16 MHz HFINTOSC and 31 kHz
LFINTOSC connects to a postscaler and multiplexer
(see Figure 8-1). The Internal Oscillator Frequency
Select bits IRCF<2:0> of the OSCCON register select
the frequency output of the internal oscillators. One of
eight frequencies can be selected via software:
• 16 MHz
• 8 MHz
• 4 MHz
• 2 MHz
• 1 MHz
• 500 kHz (Default after Reset)
• 250 kHz
• 125 kHz
• 31 kHz (LFINTOSC)
Note:
Following any Reset, the IRCF<2:0> bits of
the OSCCON register are set to ‘110’ and
the frequency selection is set to 4 MHz.
The user can modify the IRCF bits to
select a different frequency.
PIC16F193X/LF193X
8.5.8
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 8-6). 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 8-6 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 8-1.
Start-up delay specifications are located in the
oscillator tables of Section 28.0 “Electrical
Specifications”.
© 2008 Microchip Technology Inc.
Preliminary
DS41364A-page 115