PIC12F635-ISLASHST datasheet(69/234 Pages) MICROCHIP

69 / 234 page

DS41232D-page 67

PIC12F635/PIC16F636/639

6.7

Timer1 Interrupt

The Timer1 register pair (TMR1H:TMR1L) increments

to FFFFh and rolls over to 0000h. When Timer1 rolls

over, the Timer1 interrupt flag bit of the PIR1 register is

set. To enable the interrupt on rollover, you must set

these bits:

• Timer1 interrupt enable bit of the PIE1 register

• PEIE bit of the INTCON register

• GIE bit of the INTCON register

The interrupt is cleared by clearing the TMR1IF bit in

the Interrupt Service Routine.

6.8

Timer1 Operation During Sleep

Timer1 can only operate during Sleep when setup in

Asynchronous Counter mode. In this mode, an external

crystal or clock source can be used to increment the

counter. To set up the timer to wake the device:

• TMR1ON bit of the T1CON register must be set

• TMR1IE bit of the PIE1 register must be set

• PEIE bit of the INTCON register must be set

The device will wake-up on an overflow and execute

the next instruction. If the GIE bit of the INTCON

Routine (0004h).

6.9

Comparator Synchronization

The same clock used to increment Timer1 can also be

used to synchronize the comparator output. This

feature is enabled in the Comparator module.

When using the comparator for Timer1 gate, the

comparator output should be synchronized to Timer1.

This ensures Timer1 does not miss an increment if the

comparator changes.

For more information, see Section 7.0 “Comparator

Module”.

FIGURE 6-2:

TIMER1 INCREMENTING EDGE

Note:

The TMR1H:TTMR1L register pair and the

TMR1IF bit should be cleared before

enabling interrupts.

T1CKI = 1

when TMR1

Enabled

T1CKI = 0

when TMR1

Enabled

Note 1:

Arrows indicate counter increments.

In Counter mode, a falling edge must be registered by the counter prior to the first incrementing rising edge of

the clock.

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