PIC16F631/677/685/687/689/690
In Compare mode, an event is triggered when the value
CCPR1H:CCPR1L register pair matches the value in
the TMR1H:TMR1L register pair. This event can be a
Special Event Trigger.
Note:
TMR1GE bit of the T1CON register must
be set to use either T1G or C2OUT as the
Timer1 gate source. See the CM2CON1
register (Register 8-3) for more informa-
tion on selecting the Timer1 gate source.
For more information, see Section 11.0 “Enhanced
Capture/Compare/PWM Module”.
Timer1 gate can be inverted using the T1GINV bit of
the T1CON register, whether it originates from the T1G
pin or Comparator C2 output. This configures Timer1 to
measure either the active-high or active-low time
between events.
6.10 ECCP Special Event Trigger
When the ECCP is configured to trigger a special
event, the trigger will clear the TMR1H:TMR1L register
pair. This special event does not cause a Timer1 inter-
rupt. The ECCP module may still be configured to
generate a ECCP interrupt.
6.7
Timer1 Interrupt
In this mode of operation, the CCPR1H:CCPR1L
register pair becomes the period register for Timer1.
The Timer1 register pair (TMR1H:TMR1L) increments
to FFFFh and rolls over to 0000h. When Timer1 rolls
over, the Timer1 interrupt flag bit of the PIR1 register is
set. To enable the interrupt on rollover, you must set
these bits:
Timer1 should be synchronized to the FOSC to utilize
the Special Event Trigger. Asynchronous operation of
Timer1 can cause a Special Event Trigger to be
missed.
• TMR1ON bit of the T1CON register
• TMR1IE bit of the PIE1 register
• PEIE bit of the INTCON register
• GIE bit of the INTCON register
In the event that a write to TMR1H or TMR1L coincides
with a Special Event Trigger from the ECCP, the write
will take precedence.
For more information, see Section 11.2.4 “Special
Event Trigger”.
The interrupt is cleared by clearing the TMR1IF bit in
the Interrupt Service Routine.
Note:
The TMR1H:TTMR1L register pair and the
TMR1IF bit should be cleared before
enabling interrupts.
6.11 Comparator Synchronization
The same clock used to increment Timer1 can also be
used to synchronize the comparator output. This
feature is enabled in the Comparator module.
6.8
Timer1 Operation During Sleep
When using the comparator for Timer1 gate, the
comparator output should be synchronized to Timer1.
This ensures Timer1 does not miss an increment if the
comparator changes.
Timer1 can only operate during Sleep when setup in
Asynchronous Counter mode. In this mode, an external
crystal or clock source can be used to increment the
counter. To set up the timer to wake the device:
For
more
information,
see
Section 8.8.2
• TMR1ON bit of the T1CON register must be set
• TMR1IE bit of the PIE1 register must be set
• PEIE bit of the INTCON register must be set
• T1SYNC bit of the T1CON register must be set
• TMR1CS bit of the T1CON register must be set
• T1OSCEN bit of the T1CON register (can be set)
“Synchronizing Comparator C2 output to Timer1”.
The device will wake-up on an overflow and execute
the next instructions. If the GIE bit of the INTCON
register is set, the device will call the Interrupt Service
Routine (0004h).
6.9
ECCP Capture/Compare Time Base
The ECCP module uses the TMR1H:TMR1L register
pair as the time base when operating in Capture or
Compare mode.
In Capture mode, the value in the TMR1H:TMR1L
register pair is copied into the CCPR1H:CCPR1L
register pair on a configured event.
DS41262D-page 86
© 2007 Microchip Technology Inc.
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