PIC16F18345 datasheet(71/442 Pages) MICROCHIP

71 / 442 page

 2015 Microchip Technology Inc.

Preliminary

DS40001799A-page 71

PIC16(L)F18313/18323

Changing the clock post-divider without changing the

clock source (i.e., changing FOSC from 1 MHz to 2

MHz) is handled in the same manner as a clock source

change, as described previously. The clock source will

already be active, so the switch is relatively quick.

CSWHOLD must be clear (CSWHOLD = 0) for the

switch to complete.

The current COSC and CDIV are indicated in the

OSCCON2 register up to the moment when the switch

actually occurs, at which time OSCCON2 is updated

and ORDY is set. NOSCR is cleared by hardware to

indicate that the switch is complete.

6.3.2

PLL INPUT SWITCH

Switching between the PLL and any non-PLL source is

managed as described above. The input to the PLL is

established when NOSC selects the PLL, and main-

tained by the COSC setting.

When NOSC and COSC select the PLL with different

input sources, the system continues to run using the

COSC setting, and the new source is enabled per

NOSC. When the new oscillator is ready (and

CSWHOLD = 0), system operation is suspended while

the PLL input is switched and the PLL acquires lock.

6.3.3

CLOCK SWITCH AND SLEEP

If OSCCON1 is written with a new value and the device

is put to Sleep before the switch completes, the switch

will not take place and the device will enter Sleep

mode.

When the device wakes from Sleep and the

CSWHOLD bit is clear, the device will wake with the

‘new’ clock active, and the Clock Switch Interrupt Flag

bit (CSWIF) will be set.

When the device wakes from Sleep and the

CSWHOLD bit is set, the device will wake with the ‘old’

clock active and the new clock will be requested again.

FIGURE 6-6:

CLOCK SWITCH (CSWHOLD = 0)

Note 1:

CSWIF is asserted coincident with NOSCR; interrupt is serviced at OSC#2 speed.

The assertion of NOSCR is hidden from the user because it appears only for the duration of the switch.

CSWHOLD

NOSCR

OSC #2

CSWIF

OSCCON1

WRITTEN

NOTE 1

USER

CLEAR

OSC #1

NOTE 2

ORDY

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