PIC18C242 MICROCHIP [Microchip Technology], PIC18C242 Datasheet - Page 106

• Manufacturer Part Number: PIC18C242
• Description: High-Performance Microcontrollers with 10-Bit A/D
• Manufacturer: MICROCHIP [Microchip Technology]

PIC18CXX2
12.1
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>).
FIGURE 12-1: TIMER3 BLOCK DIAGRAM
FIGURE 12-2: TIMER3 BLOCK DIAGRAM CONFIGURED IN 16-BIT MODE
DS39026B-page 106
Set TMR3IF flag bit
on overflow
Note 1: When the T1OSCEN bit is cleared, the inverter and feedback resistor are turned off. This eliminates power drain.
Note 1: When enable bit T1OSCEN is cleared, the inverter and feedback resistor are turned off. This eliminates power drain.
T1OSO/
T13CKI
T1OSI
Timer3 Operation
Data bus<7:0>
Write TMR3L
Read TMR3L
T1OSO/
T13CKI
T1OSI
TMR3IF
Overflow
Interrupt
flag bit
T1OSC
8
High Byte
TMR3H
Timer3
8
To Timer1 Clock Input
TMR3H
T1OSC
Enable
Oscillator
T1OSCEN
8
TMR3
(1)
TMR3L
8
Oscillator
Enable
T1OSCEN
TMR3L
(1)
CLR
Preliminary
(3)
Internal
Clock
Fosc/4
Clock
F
Internal
TMR3ON
OSC
on/off
TMR3CS
/4
TMR3ON
When TMR3CS = 0, Timer3 increments every instruc-
tion cycle. When TMR3CS = 1, Timer3 increments on
every rising edge of the Timer1 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.
Timer3 also has an internal “reset input”. This reset can
be generated by the CCP module (Section 12.0).
on/off
1
0
TMR3CS
1
0
T3CCPx
T3CKPS1:T3CKPS0
CCP Special Trigger
T3SYNC
T3CKPS1:T3CKPS0
Prescaler
1, 2, 4, 8
T3SYNC
0
1
Prescaler
1, 2, 4, 8
2
0
1
2
Synchronized
7/99 Microchip Technology Inc.
clock input
Synchronize
SLEEP input
Synchronized
clock input
Synchronize
SLEEP input
det
det