
PIC18FXX39
DS30485A-page 104
Preliminary
2002 Microchip Technology Inc.
11.1
Timer1 Operation
Timer1 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, TMR1CS (T1CON<1>). When TMR1CS = 0,
Timer1 increments every instruction cycle. When
TMR1CS = 1, Timer1 increments on every rising edge
of the external clock input.
FIGURE 11-1:
TIMER1 BLOCK DIAGRAM
FIGURE 11-2:
TIMER1 BLOCK DIAGRAM: 16-BIT READ/WRITE MODE
TMR1H
TMR1L
T1SYNC
TMR1CS
T1CKPS1:T1CKPS0
SLEEP Input
FOSC/4
Internal
Clock
TMR1ON
On/Off
Prescaler
1, 2, 4, 8
Synchronize
det
1
0
1
Synchronized
Clock Input
2
TMR1IF
Overflow
TMR1
Interrupt
Flag bit
T13CKI
Timer 1
TMR1L
T1SYNC
TMR1CS
T1CKPS1:T1CKPS0
SLEEP Input
TMR1IF
Overflow
Interrupt
FOSC/4
Internal
Clock
TMR1ON
on/off
Prescaler
1, 2, 4, 8
Synchronize
det
1
0
1
Synchronized
Clock Input
2
T13CKI
TMR1
Flag bit
High Byte
Data Bus<7:0>
8
TMR1H
8
Read TMR1L
Write TMR1L