PIC18F258 MICROCHIP [Microchip Technology], PIC18F258 Datasheet - Page 114

• Manufacturer Part Number: PIC18F258
• Description: High Performance, 28/40-Pin Enhanced FLASH Microcontrollers with CAN
• Manufacturer: MICROCHIP [Microchip Technology]

PIC18FXX8
12.1
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 register).
FIGURE 12-1:
FIGURE 12-2:
DS41159B-page 112
Note 1: When enable bit T1OSCEN is cleared, the inverter and feedback resistor are turned off. This reduces power drain.
Note 1: When enable bit T1OSCEN is cleared, the inverter and feedback resistor are turned off. This reduces power drain.
T13CKI/T1OSO
T13CKI/T1OSO
Timer1 Operation
T1OSI
TMR1IF
Overflow
Interrupt
Flag bit
Data Bus<7:0>
Write TMR1L
Read TMR1L
TMR1IF
Overflow
Interrupt
Flag bit
T1OSI
TIMER1 BLOCK DIAGRAM
TIMER1 BLOCK DIAGRAM: 16-BIT READ/WRITE MODE
8
T1OSC
TMR1H
high byte
T1OSC
Timer 1
8
TMR1H
8
TMR1
TMR1
Oscillator
Enable
T1OSCEN
T1OSCEN
Enable
Oscillator
TMR1L
TMR1L
8
(1)
CLR
(1)
Preliminary
Clock
Internal
F
OSC
Clock
Internal
F
/4
TMR1ON
OSC
CCP Special Event Trigger
On/Off
TMR1CS
/4
TMR1ON
When TMR1CS is clear, Timer1 increments every
instruction cycle. When TMR1CS is set, Timer1 incre-
ments on every rising edge of the external clock input
or the Timer1 oscillator, if enabled.
When the Timer1 oscillator is enabled (T1OSCEN is
set), the RC1/T1OSI and RC0/T1OSO/T1CKI pins
become inputs. That is, the TRISC<1:0> value is
ignored.
Timer1 also has an internal “RESET input”. This
RESET can be generated by the CCP module
(Section 15.1).
Special Event Trigger
On/Off
1
0
TMR1CS
1
0
T1CKPS1:T1CKPS0
T1SYNC
Prescaler
1, 2, 4, 8
T1CKPS1:T1CKPS0
T1SYNC
Prescaler
0
1
1, 2, 4, 8
2
0
1
2
 2002 Microchip Technology Inc.
Synchronized
Clock Input
Synchronize
SLEEP Input
Synchronized
Clock Input
Synchronize
SLEEP Input
det
det