41594B datasheet(158/372 Pages) MICROCHIP

158 / 372 page

PIC12LF1840T48A

DS41594B-page 158

Preliminary

 2011-2012 Microchip Technology Inc.

20.1.3

SOFTWARE PROGRAMMABLE

PRESCALER

A software programmable prescaler is available for

exclusive use with Timer0. The prescaler is enabled by

clearing the PSA bit of the OPTION register.

There are 8 prescaler options for the Timer0 module

ranging from 1:2 to 1:256. The prescale values are

selectable via the PS<2:0> bits of the OPTION register.

In order to have a 1:1 prescaler value for the Timer0

module, the prescaler must be disabled by setting the

PSA bit of the OPTION register.

The prescaler is not readable or writable. All instructions

writing to the TMR0 register will clear the prescaler.

20.1.4

TIMER0 INTERRUPT

Timer0 will generate an interrupt when the TMR0

interrupt flag bit of the INTCON register is set every

time the TMR0 register overflows, regardless of

whether or not the Timer0 interrupt is enabled. The

TMR0IF bit can only be cleared in software. The Timer0

interrupt enable is the TMR0IE bit of the INTCON

20.1.5

8-BIT COUNTER MODE

SYNCHRONIZATION

When in 8-Bit Counter mode, the incrementing edge on

the T0CKI pin must be synchronized to the instruction

clock. Synchronization can be accomplished by

sampling the prescaler output on the Q2 and Q4 cycles

of the instruction clock. The high and low periods of the

external clocking source must meet the timing

requirements as shown in Section 31.0 “Electrical

Specifications”.

20.1.6

OPERATION DURING SLEEP

Timer0 cannot operate while the processor is in Sleep

mode. The contents of the TMR0 register will remain

unchanged while the processor is in Sleep mode.

Note:

The Watchdog Timer (WDT) uses its own

independent prescaler.

Note:

The Timer0 interrupt cannot wake the

processor from Sleep since the timer is

frozen during Sleep.

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