Datasheet

PIC18(L)F2X/45K50
DS30684A-page 178  2012 Microchip Technology Inc.
14.1 Timer2 Operation
The clock input to the Timer2 module is the system
instruction clock (F
OSC/4).
TMR2 increments from 00h on each clock edge.
A 4-bit counter/prescaler on the clock input allows direct
input, divide-by-4 and divide-by-16 prescale options.
These options are selected by the prescaler control bits,
T2CKPS<1:0> of the T2CON register. The value of
TMR2 is compared to that of the Period register, PR2, on
each clock cycle. When the two values match, the
comparator generates a match signal as the timer
output. This signal also resets the value of TMR2 to 00h
on the next cycle and drives the output
counter/postscaler (see Section 14.2 “Timer2
Interrupt”).
The TMR2 and PR2 registers are both directly readable
and writable. The TMR2 register is cleared on any
device Reset, whereas the PR2 register initializes to
FFh. Both the prescaler and postscaler counters are
cleared on the following events:
• a write to the TMR2 register
• a write to the T2CON register
• Power-on Reset (POR)
• Brown-out Reset (BOR)
•MCLR
Reset
• Watchdog Timer (WDT) Reset
• Stack Overflow Reset
• Stack Underflow Reset
• RESET Instruction
14.2 Timer2 Interrupt
Timer2 can also generate an optional device interrupt.
The Timer2 output signal (TMR2-to-PR2 match)
provides the input for the 4-bit counter/postscaler. This
counter generates the TMR2 match interrupt flag which
is latched in TMR2IF of the PIR1 register. The interrupt
is enabled by setting the TMR2 Match Interrupt Enable
bit, TMR2IE of the PIE1 register. Interrupt Priority is
selected with the TMR2IP bit in the IPR1 register.
A range of 16 postscale options (from 1:1 through 1:16
inclusive) can be selected with the postscaler control
bits, T2OUTPS<3:0>, of the T2CON register.
14.3 Timer2 Output
The unscaled output of TMR2 is available primarily to
the CCP modules, where it is used as a time base for
operations in PWM mode.
Timer2 can be optionally used as the shift clock source
for the MSSP module operating in SPI mode by setting
SSPM<3:0> = 0011 in the SSPxCON1 register.
Additional information is provided in Section 16.0
“Master Synchronous Serial Port (MSSP) Module”.
14.4 Timer2 Operation During Sleep
The Timer2 timers cannot be operated while the
processor is in Sleep mode. The contents of the TMR2
and PR2 registers will remain unchanged while the
processor is in Sleep mode.
14.5 Peripheral Module Disable
When a peripheral module is not used or inactive, the
module can be disabled by setting the Module Disable
bit in the PMD registers. This will reduce power con-
sumption to an absolute minimum. Setting the PMD
bits holds the module in Reset and disconnects the
module’s clock source. The Module Disable bit for
Timer2 (TMR2MD) is in the PMD0 register. See
Section 4.0 “Power-Managed Modes” for more
information.
Note: TMR2 is not cleared when T2CON is
written.