PIC12F683_07 datasheet(48/176 Pages) MICROCHIP

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PIC12F683

DS41211D-page 46

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

CCP Special Event Trigger

If a CCP is configured to trigger a special event, the

trigger will clear the TMR1H:TMR1L register pair. This

special event does not cause a Timer1 interrupt. The

CCP module may still be configured to generate a CCP

interrupt.

In this mode of operation, the CCPR1H:CCPR1L regis-

ter pair effectively becomes the period register for

Timer1.

Timer1 should be synchronized to the FOSC to utilize

the Special Event Trigger. Asynchronous operation of

Timer1 can cause a Special Event Trigger to be

missed.

In the event that a write to TMR1H or TMR1L coincides

with a Special Event Trigger from the CCP, the write will

take precedence.

For more information, see Section on CCP.

6.10

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 8.0 “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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