PIC16F1825T-ESS datasheet(59/448 Pages) MICROCHIP

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 2010-2012 Microchip Technology Inc.

DS41440C-page 59

PIC16(L)F1825/1829

5.2.1.4

4xPLL

The oscillator module contains a 4xPLL that can be

used with both external and internal clock sources to

provide a system clock source. The input frequency for

the 4xPLL must fall within specifications. See the PLL

Clock

Timing

Specifications

Section 30.0

“Electrical Specifications”.

The 4xPLL may be enabled for use by one of two

methods:

Program the PLLEN bit in Configuration Word 2

to a ‘1’.

Write the SPLLEN bit in the OSCCON register to

a ‘1’. If the PLLEN bit in Configuration Word 2 is

programmed to a ‘1’, then the value of SPLLEN

is ignored.

5.2.1.5

TIMER1 Oscillator

The Timer1 Oscillator is a separate crystal oscillator

that is associated with the Timer1 peripheral. It is

optimized for timekeeping operations with a 32.768

kHz crystal connected between the T1OSO and T1OSI

device pins.

The Timer1 Oscillator can be used as an alternate

system clock source and can be selected during

run-time using clock switching. Refer to Section 5.3

“Clock Switching” for more information.

FIGURE 5-5:

QUARTZ CRYSTAL

OPERATION (TIMER1

OSCILLATOR)

5.2.1.6

External RC Mode

The external Resistor-Capacitor (RC) modes support

the use of an external RC circuit. This allows the

designer maximum flexibility in frequency choice while

keeping costs to a minimum when clock accuracy is not

required.

The RC circuit connects to OSC1. OSC2/CLKOUT is

available for general purpose I/O or CLKOUT. The

function of the OSC2/CLKOUT pin is determined by the

state of the CLKOUTEN bit in Configuration Word 1.

Figure 5-6 shows the external RC mode connections.

32.768 kHz

T1OSI

To Internal

Logic

PIC® MCU

Crystal

T1OSO

Quartz

Note 1: Quartz

crystal

characteristics

vary

according

type,

package

and

manufacturer. The user should consult the

manufacturer data sheets for specifications

and recommended application.

2: Always verify oscillator performance over

the VDD and temperature range that is

expected for the application.

3: For oscillator design assistance, reference

the following Microchip Application Notes:

• AN826, “Crystal Oscillator Basics and

Crystal Selection for rfPIC® and PIC®

Devices” (DS00826)

• AN849, “Basic PIC® Oscillator Design”

(DS00849)

• AN943, “Practical PIC® Oscillator

Analysis and Design” (DS00943)

• AN949, “Making Your Oscillator Work”

(DS00949)

• TB097, “Interfacing a Micro Crystal

MS1V-T1K 32.768 kHz Tuning Fork

Crystal to a PIC16F690/SS” (DS91097)

• AN1288, “Design Practices for

Low-Power External Oscillators”

(DS01288)

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