PIC16F946 Datasheet, PDF (90/274 Pages) Microchip Technology – 64-Pin Flash-Based, 8-Bit CMOS Microcontrollers with LCD Driver and nanoWatt Technology

PIC16F946
6.1 Timer1 Modes of Operation
Timer1 can operate in one of three modes:
• 16-bit timer with prescaler
• 16-bit synchronous counter
• 16-bit asynchronous counter
In Timer mode, Timer1 is incremented on every
instruction cycle. In Counter mode, Timer1 is incremented
on the rising edge of the external clock input T1CKI. In
addition, the Counter mode clock can be synchronized to
the microcontroller system clock or run asynchronously.
In the Timer1 module, the module clock can be gated
by the Timer1 gate, which can be selected as either the
T1G pin or Comparator 2 output.
If an external clock oscillator is needed (and the
microcontroller is using the INTOSC without CLKO),
Timer1 can use the LP oscillator as a clock source.
Note:
In Counter mode, a falling edge must be
registered by the counter prior to the first
incrementing rising edge.
6.2 Timer1 Interrupt
The Timer1 register pair (TMR1H:TMR1L) increments
to FFFFh and rolls over to 0000h. When Timer1 rolls
over, the Timer1 Interrupt Flag bit (PIR1<0>) is set. To
enable the interrupt on rollover, you must set these bits:
• Timer1 Interrupt Enable bit (PIE1<0>)
• PEIE bit (INTCON<6>)
• GIE bit (INTCON<7>)
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.
6.3 Timer1 Prescaler
Timer1 has four prescaler options allowing 1, 2, 4 or 8
divisions of the clock input. The T1CKPS bits
(T1CON<5:4>) control the prescale counter. The
prescale counter is not directly readable or writable;
however, the prescaler counter is cleared upon a write
to TMR1H or TMR1L.
6.4 Timer1 Gate
Timer1 gate source is software configurable to be the
T1G pin or the output of Comparator 2. This allows the
device to directly time external events using T1G or
analog events using Comparator 2. See CMCON1
(Register 8-2) for selecting the Timer1 gate source.
This feature can simplify the software for a Delta-Sigma
A/D converter and many other applications. For more
information on Delta-Sigma A/D converters, see the
Microchip web site (www.microchip.com).
Note:
T1GE bit (T1CON<6>) must be set to use
either T1G or C2OUT as the Timer1 gate
source. See Register 8-2 for more
information on selecting the Timer1 gate
source.
Timer1 gate can be inverted using the T1GINV bit
(T1CON<7>), whether it originates from the T1G pin or
Comparator 2 output. This configures Timer1 to
measure either the active-high or active-low time
between events.
FIGURE 6-2:
T1CKI = 1
when TMR1
Enabled
TIMER1 INCREMENTING EDGE
T1CKI = 0
when TMR1
Enabled
Note 1: Arrows indicate counter increments.
2: In Counter mode, a falling edge must be registered by the counter prior to the first incrementing
rising edge of the clock.
DS41265A-page 88
Preliminary
© 2005 Microchip Technology Inc.