
PIC18FXX39
DS30485A-page 110
Preliminary
2002 Microchip Technology Inc.
13.1
Timer3 Operation
Timer3 can operate in one of these modes:
As a timer
As a synchronous counter
As an asynchronous counter
The Operating mode is determined by the clock select
bit, TMR3CS (T3CON<1>). When TMR3CS = 0,
Timer3 increments every instruction cycle. When
TMR3CS = 1, Timer3 increments on every rising edge
of the Timer1 external clock input.
FIGURE 13-1:
TIMER3 BLOCK DIAGRAM
FIGURE 13-2:
TIMER3 BLOCK DIAGRAM CONFIGURED IN 16-BIT READ/WRITE MODE
TMR3H
TMR3L
T3SYNC
TMR3CS
T3CKPS1:T3CKPS0
SLEEP Input
TMR3IF
Overflow
Interrupt
FOSC/4
Internal
Clock
TMR3ON
On/Off
Prescaler
1, 2, 4, 8
Synchronize
det
1
0
1
Synchronized
Clock Input
2
Flag bit
T13CKI
Timer3
TMR3L
T3SYNC
TMR3CS
T3CKPS1:T3CKPS0
SLEEP Input
FOSC/4
Internal
Clock
TMR3ON
On/Off
Prescaler
1, 2, 4, 8
Synchronize
det
1
0
1
Synchronized
Clock Input
2
TMR3
T13CKI
To Timer1 Clock Input
High Byte
Data Bus<7:0>
8
TMR3H
8
Read TMR3L
Write TMR3L
Set TMR3IF Flag bit
on Overflow