PIC18F258 Datasheet, PDF (121/384 Pages) Microchip Technology – High Performance, 28/40-Pin Enhanced FLASH Microcontrollers with CAN

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 200 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 FFFFh and rolls over to 0000h. The TMR3
Interrupt, if enabled, is generated on overflow, which is
latched in interrupt flag bit TMR3IF (PIR registers). 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
If the CCP module is configured in Compare mode to
generate a “special event trigger" (CCP1M3:CCP1M0
= 1011), this signal will reset Timer3.
Note:
The special event triggers from the CCP
module will not set interrupt flag bit
TMR3IF (PIR registers).
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 registers 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
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 -0-0 0000 -0-0 0000
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.
 2002 Microchip Technology Inc.
Preliminary
DS41159B-page 119