Datasheet

PIC16F631/677/685/687/689/690
DS40001262F-page 82  2005-2015 Microchip Technology Inc.
6.0 TIMER1 MODULE WITH GATE
CONTROL
The Timer1 module is a 16-bit timer/counter with the
following features:
• 16-bit timer/counter register pair (TMR1H:TMR1L)
• Programmable internal or external clock source
• 3-bit prescaler
• Optional LP oscillator
• Synchronous or asynchronous operation
• Timer1 gate (count enable) via comparator or
T1G
pin
• Interrupt on overflow
• Wake-up on overflow (external clock,
Asynchronous mode only)
• Time base for the Capture/Compare function
(PIC16F685/PIC16F690 only)
• Special Event Trigger (with ECCP)
(PIC16F685/PIC16F690 only)
• Comparator output synchronization to Timer1
clock
Figure 6-1 is a block diagram of the Timer1 module.
6.1 Timer1 Operation
The Timer1 module is a 16-bit incrementing counter
which is accessed through the TMR1H:TMR1L register
pair. Writes to TMR1H or TMR1L directly update the
counter.
When used with an internal clock source, the module is
a timer. When used with an external clock source, the
module can be used as either a timer or counter.
6.2 Clock Source Selection
The TMR1CS bit of the T1CON register is used to select
the clock source. When TMR1CS = 0, the clock source
is F
OSC/4. When TMR1CS = 1, the clock source is
supplied externally.
Clock
Source
T1OSCEN
FOSC
Mode
TMR1CS
F
OSC/4 x xxx 0
T1CKI pin 0 xxx 1
T1LPOSC 1 LP or
INTOSCIO
1