PIC16F684 datasheet(55/192 Pages) MICROCHIP

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DS41202F-page 53

PIC16F684

7.0

TIMER2 MODULE

The Timer2 module is an eight-bit timer with the

following features:

• 8-bit timer register (TMR2)

• 8-bit period register (PR2)

• Interrupt on TMR2 match with PR2

• Software programmable prescaler (1:1, 1:4, 1:16)

• Software programmable postscaler (1:1 to 1:16)

See Figure 7-1 for a block diagram of Timer2.

7.1

Timer2 Operation

The clock input to the Timer2 module is the system

instruction clock (FOSC/4). The clock is fed into the

Timer2 prescaler, which has prescale options of 1:1,

1:4 or 1:16. The output of the prescaler is then used to

increment the TMR2 register.

The values of TMR2 and PR2 are constantly compared

to determine when they match. TMR2 will increment

from 00h until it matches the value in PR2. When a

match occurs, two things happen:

• TMR2 is reset to 00h on the next increment cycle.

• The Timer2 postscaler is incremented

The match output of the Timer2/PR2 comparator is fed

into the Timer2 postscaler. The postscaler has

postscale options of 1:1 to 1:16 inclusive. The output of

the Timer2 postscaler is used to set the TMR2IF

interrupt flag bit in the PIR1 register.

The TMR2 and PR2 registers are both fully readable

and writable. On any Reset, the TMR2 register is set to

00h and the PR2 register is set to FFh.

Timer2 is turned on by setting the TMR2ON bit in the

T2CON register to a ‘1’. Timer2 is turned off by clearing

the TMR2ON bit to a ‘0’.

The Timer2 prescaler is controlled by the T2CKPS bits

in the T2CON register. The Timer2 postscaler is

controlled by the TOUTPS bits in the T2CON register.

The prescaler and postscaler counters are cleared

when:

• A write to TMR2 occurs.

• A write to T2CON occurs.

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

Reset, Watchdog Timer Reset, or Brown-out

Reset).

FIGURE 7-1:

TIMER2 BLOCK DIAGRAM

Note:

TMR2 is not cleared when T2CON is

written.

Comparator

TMR2

Sets Flag

TMR2

Output

Reset

Postscaler

Prescaler

PR2

FOSC/4

1:1 to 1:16

1:1, 1:4, 1:16

bit TMR2IF

TOUTPS<3:0>

T2CKPS<1:0>

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