PIC18F44K22T-I/SO View Datasheet(PDF) - Microchip Technology

Part Name

Description

Manufacturer

PIC18F44K22T-I/SO

28/40/44-Pin, Low-Power,High-Performance Microcontrollers with XLP Technology

Microchip Technology 

PIC18(L)F2X/4XK22

2.10.2 TWO-SPEED START-UP

SEQUENCE

1. Wake-up from Power-on Reset or Sleep.

2. Instructions begin executing by the internal

oscillator at the frequency set in the IRCF<2:0>

bits of the OSCCON register.

3. OST enabled to count 1024 external clock

cycles.

4. OST timed out. External clock is ready.

5. OSTS is set.

6. Clock switch finishes according to Figure 2-9

FIGURE 2-9:

CLOCK SWITCH TIMING

High Speed Low Speed

2.10.3 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 CONFIG1H Configuration register,

or the internal oscillator. OSTS = 0 when the external

oscillator is not ready, which indicates that the system

is running from the internal oscillator.

Old Clock

Start-up Time(1)

New Clock

New Clk Ready

IRCF <2:0> Select Old

Select New

System Clock

Clock Sync

Running

Low Speed High Speed

Old Clock

Start-up Time(1)

New Clock

New Clk Ready

IRCF <2:0> Select Old

Select New

System Clock

Clock Sync

Running

Note 1: Start-up time includes TOST (1024 TOSC) for external clocks, plus TPLL (approx. 2 ms) for HSPLL mode.

 2010 Microchip Technology Inc.

Preliminary

DS41412A-page 43

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