Microchip Technology DM164134 Data Sheet
© 2006 Microchip Technology Inc.
DS41159E-page 121
PIC18FXX8
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 bit (T1CON register). The oscillator is a
low-power oscillator rated up to 50 kHz. Refer to
Section 12.0 “Timer1 Module” for Timer1 oscillator
details.
for Timer3. The Timer1 oscillator is enabled by setting
the T1OSCEN bit (T1CON register). The oscillator is a
low-power oscillator rated up to 50 kHz. Refer to
Section 12.0 “Timer1 Module” for Timer1 oscillator
details.
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 (PIR regis-
ters). This interrupt can be enabled/disabled by setting/
clearing TMR3 Interrupt Enable bit, TMR3IE (PIE
registers).
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 (PIR regis-
ters). This interrupt can be enabled/disabled by setting/
clearing TMR3 Interrupt Enable bit, TMR3IE (PIE
registers).
14.4
Resetting Timer3 Using a CCP
Trigger Output
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.
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 becomes
the period register for Timer3. Refer to Section 15.0
“Capture/Compare/PWM (CCP) Modules” for CCP
details.
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 becomes
the period register for Timer3. Refer to Section 15.0
“Capture/Compare/PWM (CCP) Modules” for CCP
details.
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 (PIR registers).
module will not set interrupt flag bit
TMR3IF (PIR registers).
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 000x 0000 000u
PIR2
—
CMIF
—
EEIF
BCLIF
LVDIF
TMR3IF
ECCP1IF -0-0 0000 -0-0 0000
PIE2
—
CMIE
—
EEIE
BCLIE
LVDIE
TMR3IE
ECCP1IE -0-0 0000 -0-0 0000
IPR2
—
CMIP
—
EEIP
BCLIP
LVDIP
TMR3IP
ECCP1IP -1-1 1111 -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
T3ECCP1
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 Timer1 module.