PIC12F1822-ISLASHMF datasheet(176/398 Pages) MICROCHIP

176 / 398 page

PIC12F/LF1822/16F/LF1823

DS41413A-page 176

Preliminary

 2010 Microchip Technology Inc.

20.7

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:

• TMR1ON bit of the T1CON register

• TMR1IE 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.

20.8

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

• T1SYNC bit of the T1CON register must be set

• TMR1CS bits of the T1CON register must be

configured

• T1OSCEN bit of the T1CON register must be

configured

The device will wake-up on an overflow and execute

the next instructions. If the GIE bit of the INTCON

Routine.

Timer1 oscillator will continue to operate in Sleep

regardless of the T1SYNC bit setting.

20.9

ECCP/CCP Capture/Compare Time

Base

The CCP1 module uses the TMR1H:TMR1L register

pair as the time base when operating in Capture or

Compare mode.

In Capture mode, the value in the TMR1H:TMR1L

In Compare mode, an event is triggered when the value

CCPR1H:CCPR1L register pair matches the value in

the TMR1H:TMR1L register pair. This event can be a

Special Event Trigger.

For

information,

see

Section 23.0

“Capture/Compare/PWM Modules”.

20.10 ECCP/CCP Special Event Trigger

When any of the CCP’s are configured to trigger a spe-

cial event, the trigger will clear the TMR1H:TMR1L reg-

ister pair. This special event does not cause a Timer1

interrupt. The CCP1 module may still be configured to

generate a CCP interrupt.

In this mode of operation, the CCPR1H:CCPR1L

Timer1 should be synchronized and FOSC/4 should be

selected as the clock source in order to utilize the Spe-

cial 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 15.2.5 “Special

Event Trigger”.

FIGURE 20-2:

TIMER1 INCREMENTING EDGE

Note:

The TMR1H:TMR1L 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.

2: 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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