PIC18F6585/8585/6680/8680
DS30491C-page 166
2004 Microchip Technology Inc.
14.2
Timer1 Oscillator
The Timer1 oscillator may be used as the clock source
for Timer3. The Timer1 oscillator is enabled by setting
the T1OSCEN (T1CON<3>) bit. The oscillator is a low-
14.3
Timer3 Interrupt
The TMR3 register pair (TMR3H:TMR3L) increments
from 0000h to 0FFFFh and rolls over to 0000h. The
TMR3 interrupt, if enabled, is generated on overflow
which is
latched in interrupt
flag
bit, TMR3IF
(PIR2<1>). This interrupt can be enabled/disabled by
setting/clearing TMR3 interrupt enable bit, TMR3IE
(PIE2<1>).
14.4
Resetting Timer3 Using a CCP
Trigger Output
If the CCP module is configured in Compare mode
to
generate
a
“special
event
trigger”
(CCP1M3:CCP1M0 = 1011), this signal will reset
Timer3.
Timer3 must be configured for either Timer or Synchro-
nized Counter mode to take advantage of this feature.
If Timer3 is running in Asynchronous Counter mode,
this Reset operation may not work. In the event that a
write to Timer3 coincides with a special event trigger
from CCP1, the write will take precedence. In this mode
of operation, the CCPR1H:CCPR1L register pair
effectively becomes the period register for Timer3.
TABLE 14-1:
REGISTERS ASSOCIATED WITH TIMER3 AS A TIMER/COUNTER
Note:
The special event triggers from the CCP
module will not set interrupt flag bit,
TMR3IF (PIR1<0>).
Name
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Value on
POR, BOR
Value on
all other
Resets
INTCON
GIE/
GIEH
PEIE/
GIEL
TMR0IE
INT0IE
RBIE
TMR0IF
INT0IF
RBIF
0000 0000
PIR2
—
CMIF
—
EEIF
BCLIF
LVDIF
TMR3IF
CCP2IF
-0-0 0000
PIE2
—
CMIE
—
EEIE
BCLIE
LVDIE
TMR3IE
CCP2IE
-0-0 0000
IPR2
—
CMIP
—
EEIP
BCLIP
LVDIP
TMR3IP
CCP2IP
-1-1 1111
TMR3L
Holding Register for the Least Significant Byte of the 16-bit TMR3 Register
xxxx xxxx
uuuu uuuu
TMR3H
Holding Register for the Most Significant Byte of the 16-bit TMR3 Register
xxxx xxxx
uuuu uuuu
T1CON
RD16
—
T1CKPS1 T1CKPS0 T1OSCEN
T1SYNC
TMR1CS
TMR1ON
0-00 0000
u-uu uuuu
T3CON
RD16
T3CCP2
T3CKPS1 T3CKPS0
T3CCP1
T3SYNC
TMR3CS
TMR3ON
0000 0000
uuuu uuuu
Legend:
x
= unknown, u = unchanged, – = unimplemented, read as ‘0’. Shaded cells are not used by the Timer3 module.