PIC16F818-ESLASHML datasheet(65/176 Pages) MICROCHIP

65 / 176 page

 2004 Microchip Technology Inc.

DS39598E-page 63

PIC16F818/819

8.0

TIMER2 MODULE

Timer2 is an 8-bit timer with a prescaler and a

postscaler. It can be used as the PWM time base for the

PWM mode of the CCP1 module. The TMR2 register is

readable and writable and is cleared on any device

Reset.

The input clock (FOSC/4) has a prescale option of 1:1,

1:4

1:16,

selected

control

bits,

T2CKPS1:T2CKPS0 (T2CON<1:0>).

The Timer2 module has an 8-bit period register, PR2.

Timer2 increments from 00h until it matches PR2 and

then resets to 00h on the next increment cycle. PR2 is

a readable and writable register. The PR2 register is

initialized to FFh upon Reset.

The match output of TMR2 goes through a 4-bit

postscaler (which gives a 1:1 to 1:16 scaling inclusive)

to generate a TMR2 interrupt (latched in flag bit,

TMR2IF (PIR1<1>)).

Timer2 can be shut-off by clearing control bit, TMR2ON

(T2CON<2>), to minimize power consumption.

Additional information on timer modules is available in

the “PICmicro® Mid-Range MCU Family Reference

Manual” (DS33023).

8.1

Timer2 Prescaler and Postscaler

The prescaler and postscaler counters are cleared

when any of the following occurs:

• A write to the TMR2 register

• A write to the T2CON register

• Any device Reset (Power-on Reset, MCLR, WDT

Reset or Brown-out Reset)

TMR2 is not cleared when T2CON is written.

8.2

Output of TMR2

The output of TMR2 (before the postscaler) is fed to the

Synchronous Serial Port module which optionally uses

it to generate a shift clock.

FIGURE 8-1:

TIMER2 BLOCK DIAGRAM

Comparator

TMR2

Sets Flag

TMR2 reg

Output(1)

Reset

Postscaler

Prescaler

PR2 reg

FOSC/4

1:1

1:16

1:1, 1:4, 1:16

bit TMR2IF

Note

1: TMR2 register output can be software

selected by the SSP module as a baud clock.

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