PIC18F45J10 FAMILY
When Timer1 is enabled, the RC1/T1OSI and
RC0/T1OSO/T1CKI pins become inputs. This means
the values of TRISC<1:0> are ignored and the pins are
read as ‘0’.
12.1 Timer1 Operation
Timer1 can operate in one of these modes:
• Timer
• Synchronous Counter
• Asynchronous Counter
The operating mode is determined by the clock select
bit, TMR1CS (T1CON<1>). When TMR1CS is cleared
(= 0), Timer1 increments on every internal instruction
cycle (FOSC/4). When the bit is set, Timer1 increments
on every rising edge of the Timer1 external clock input
or the Timer1 oscillator, if enabled.
FIGURE 12-1:
TIMER1 BLOCK DIAGRAM
Timer1 Clock Input
Timer1 Oscillator
1
0
On/Off
T1OSO/T1CKI
T1OSI
1
Synchronize
Detect
Prescaler
1, 2, 4, 8
FOSC/4
Internal
Clock
0
2
Sleep Input
T1OSCEN(1)
T1CKPS<1:0>
T1SYNC
Timer1
On/Off
TMR1CS
TMR1ON
Set
TMR1
High Byte
Clear TMR1
(CCP Special Event Trigger)
TMR1L
TMR1IF
on Overflow
Note 1: When enable bit, T1OSCEN, is cleared, the inverter and feedback resistor are turned off to eliminate power drain.
DS39682E-page 120
© 2009 Microchip Technology Inc.
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