PIC16F877ATISLASHML datasheet(63/234 Pages) MICROCHIP

63 / 234 page

 2003 Microchip Technology Inc.

DS39582B-page 61

PIC16F87XA

7.0

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 CCP module(s). 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).

FIGURE 7-1:

TIMER2 BLOCK DIAGRAM

T2CON: TIMER2 CONTROL REGISTER (ADDRESS 12h)

Comparator

TMR2

Sets Flag

TMR2 Reg

Output(1)

Reset

Postscaler

Prescaler

PR2 Reg

FOSC/4

1:1 to 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.

T2OUTPS3:

T2OUTPS0

T2CKPS1:

T2CKPS0

U-0

R/W-0

—

TOUTPS3 TOUTPS2 TOUTPS1 TOUTPS0 TMR2ON

T2CKPS1 T2CKPS0

bit 7

bit 0

bit 7

Unimplemented: Read as ‘0’

bit 6-3

TOUTPS3:TOUTPS0: Timer2 Output Postscale Select bits

0000

= 1:1 postscale

0001

= 1:2 postscale

0010

= 1:3 postscale

•

1111

= 1:16 postscale

bit 2

TMR2ON: Timer2 On bit

= Timer2 is on

= Timer2 is off

bit 1-0

T2CKPS1:T2CKPS0: Timer2 Clock Prescale Select bits

= Prescaler is 1

= Prescaler is 4

= Prescaler is 16

Legend:

R = Readable bit

W = Writable bit

U = Unimplemented bit, read as ‘0’

- n = Value at POR

‘1’ = Bit is set

‘0’ = Bit is cleared

x = Bit is unknown

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