PIC18F1XK22 Datasheet, PDF (110/388 Pages) Microchip Technology – 20-Pin Flash Microcontrollers with nanoWatt XLP Technology

PIC18F1XK22/LF1XK22
12.1 Timer3 Operation
Timer3 can operate in one of three modes:
• Timer
• Synchronous Counter
• Asynchronous Counter
The operating mode is determined by the clock select
bit, TMR3CS of the T3CON register. When TMR3CS is
cleared (= 0), Timer3 increments on every internal
instruction cycle (FOSC/4). When the bit is set, Timer3
increments on every rising edge of the Timer1 external
clock input or the Timer1 oscillator, if enabled.
As with Timer1, the digital circuitry associated with the
OSC1 and OSC2 pins is disabled when the Timer1
oscillator is enabled. This means the values of
TRISA<5:4> are ignored and the pins are read as ‘0’.
FIGURE 12-1:
TIMER3 BLOCK DIAGRAM
Timer1 Oscillator
Timer1 Clock Input
1
OSC1/T13CKI
OSC2
INTOSC
Without CLKOUT
T1OSCEN⁽¹⁾
1
FOSC/4
Internal
Clock
0
TMR3CS
Prescaler
1, 2, 4, 8
2
Synchronize
Detect
0
Sleep Input
T3CKPS<1:0>
T3SYNC
TMR3ON
Timer3
On/Off
CCP1 Special Event Trigger
CCP1 Select from T3CON<3>
Clear TMR3
TMR3L
TMR3
High Byte
Set
TMR3IF
on Overflow
Note 1: When enable bit, T1OSCEN, is cleared, the inverter and feedback resistor are turned off to eliminate power drain.
DS41365D-page 110
Preliminary
 2010 Microchip Technology Inc.