Datasheet

 2010-2012 Microchip Technology Inc. DS39977F-page 209
PIC18F66K80 FAMILY
14.0 TIMER1 MODULE
The Timer1 timer/counter module incorporates these
features:
• Software selectable operation as a 16-bit timer or
counter
• Readable and writable 8-bit registers (TMR1H
and TMR1L)
• Selectable clock source (internal or external) with
device clock or SOSC oscillator internal options
• Interrupt-on-overflow
• Reset on ECCP Special Event Trigger
• Timer with gated control
Figure 14-1 displays a simplified block diagram of the
Timer1 module.
The module derives its clocking source from either the
secondary oscillator or from an external digital source.
If using the secondary oscillator, there are the addi-
tional options for low-power, high-power and external
digital clock source.
Timer1 is controlled through the T1CON Control
register (Register 14-1). It also contains the Timer1
Oscillator Enable bit (SOSCEN). Timer1 can be
enabled or disabled by setting or clearing control bit,
TMR1ON (T1CON<0>).
The F
OSC clock source should not be used with the
ECCP capture/compare features. If the timer will be
used with the capture or compare features, always
select one of the other timer clocking options.
REGISTER 14-1: T1CON: TIMER1 CONTROL REGISTER
R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0 R/W-0
TMR1CS1 TMR1CS0 T1CKPS1 T1CKPS0
SOSCEN T1SYNC RD16 TMR1ON
bit 7 bit 0
Legend:
R = Readable bit W = Writable bit U = Unimplemented bit, read as ‘0’
-n = Value at POR ‘1’ = Bit is set ‘0’ = Bit is cleared x = Bit is unknown
bit 7-6
TMR1CS<1:0>: Timer1 Clock Source Select bits
10 = Timer1 clock source is either from pin or oscillator, depending on the SOSCEN bit:
SOSCEN =
0:
External clock is from the T1CKI pin (on the rising edge).
SOSCEN =
1:
Depending on the SOSCSELx Configuration bit, the clock source is either a crystal oscillator on
SOSCI/SOSCO or an internal digital clock from the SCLKI pin.
01 = Timer1 clock source is the system clock (FOSC)
(1)
00 = Timer1 clock source is the instruction clock (FOSC/4)
bit 5-4
T1CKPS<1:0>: Timer1 Input Clock Prescale Select bits
11 = 1:8 Prescale value
10 = 1:4 Prescale value
01 = 1:2 Prescale value
00 = 1:1 Prescale value
bit 3
SOSCEN: SOSC Oscillator Enable bit
1 = SOSC is enabled and available for Timer1
0 = SOSC is disabled for Timer1
The oscillator inverter and feedback resistor are turned off to
eliminate power drain.
bit 2
T1SYNC: Timer1 External Clock Input Synchronization Select bit
TMR1CS<1:0> =
10:
1 = Do not synchronize external clock input
0 = Synchronizes external clock input
TMR1CS<1:0> = 0x:
This bit is ignored. Timer1 uses the internal clock when TMR1CS<1:0> =
1x.
Note 1: The FOSC clock source should not be selected if the timer will be used with the ECCP capture/compare
features.