PIC16F720-ESLASHML datasheet(96/244 Pages) MICROCHIP

96 / 244 page

PIC16F/LF720/721

DS41430A-page 96

 2010 Microchip Technology Inc.

13.1

Timer1 Operation

The Timer1 module is a 16-bit incrementing counter

which is accessed through the TMR1H:TMR1L register

pair. Writes to TMR1H or TMR1L directly update the

counter.

When used with an internal clock source, the module is

a timer and increments on every instruction cycle.

When used with an external clock source, the module

can be used as either a timer or counter and

increments on every selected edge of the external

source.

Timer1 is enabled by configuring the TMR1ON and

TMR1GE bits in the T1CON and T1GCON registers,

respectively. Table 13-1 displays the Timer1 enable

selections.

13.2

Clock Source Selection

The TMR1CS<1:0> bits of the T1CON register are used

to select the clock source for Timer1. Table 13-2 displays

the clock source selections.

13.2.1

INTERNAL CLOCK SOURCE

When the internal clock source is selected the

TMR1H:TMR1L register pair will increment on multiples

of FOSC as determined by the Timer1 prescaler.

13.2.2

EXTERNAL CLOCK SOURCE

When the external clock source is selected, the Timer1

module may work as a timer or a counter. When enabled

to count, Timer1 is incremented on the rising edge of the

external clock input T1CKI.

TABLE 13-1:

TIMER1 ENABLE

SELECTIONS

TMR1ON

TMR1GE

Timer1

Operation

Off

Always On

Count Enabled

Note:

In Counter mode, a falling edge must be

registered by the counter prior to the first

incrementing rising edge after any one or

more of the following conditions:

•Timer1 enabled after POR Reset

•Write to TMR1H or TMR1L

•Timer1 is disabled

•Timer1 is disabled (TMR1ON = 0)

when T1CKI is high then Timer1 is

enabled (TMR1ON=1) when T1CKI is

low.

TABLE 13-2:

CLOCK SOURCE SELECTIONS

TMR1CS1

TMR1CS0

Clock Source

System Clock (FOSC)

Instruction Clock (FOSC/4)

External Clocking on T1CKI Pin

Reserved

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