PIC16F1847_13 Datasheet, PDF (174/440 Pages) Microchip Technology – 18/20/28-Pin Flash Microcontrollers with XLP Technology

PIC16(L)F1847
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_REG register.
Note: The Watchdog Timer (WDT) uses its own
independent prescaler.
There are eight 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_REG 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_REG
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
register overflows from FFh to 00h. The TMR0IF
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 register.
Note:
The Timer0 interrupt cannot wake the
processor from Sleep since the timer is
frozen during Sleep.
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 30.0 “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.
DS40001453D-page 174
Preliminary
 2011-2013 Microchip Technology Inc.