PIC18F2420 MICROCHIP [Microchip Technology], PIC18F2420 Datasheet - Page 138

• Manufacturer Part Number: PIC18F2420
• Description: 28/40/44-Pin Enhanced Flash Microcontrollers with 10-Bit A/D and nanoWatt Technology
• Manufacturer: MICROCHIP [Microchip Technology]

PIC18F2420/2520/4420/4520
14.1
Timer3 can operate in one of three modes:
• Timer
• Synchronous Counter
• Asynchronous Counter
FIGURE 14-1:
FIGURE 14-2:
DS39631A-page 136
T1OSO/T13CKI
Note 1: When enable bit, T1OSCEN, is cleared, the inverter and feedback resistor are turned off to eliminate power drain.
Note 1: When enable bit, T1OSCEN, is cleared, the inverter and feedback resistor are turned off to eliminate power drain.
T13CKI/T1OSO
Timer3 Operation
T1OSI
T1OSI
CCP1/CCP2 Select from T3CON<6,3>
CCP1/CCP2 Select from T3CON<6,3>
CCP1/CCP2 Special Event Trigger
CCP1/CCP2 Special Event Trigger
Timer1 Oscillator
T1OSCEN
T3CKPS1:T3CKPS0
T3SYNC
TMR3ON
Timer1 Oscillator
T1OSCEN
T3CKPS1:T3CKPS0
T3SYNC
TMR3ON
TIMER3 BLOCK DIAGRAM
TIMER3 BLOCK DIAGRAM (16-BIT READ/WRITE MODE)
(1)
(1)
TMR3CS
TMR3CS
Clock
Internal
Internal
Clock
F
F
OSC
OSC
/4
/4
Preliminary
1
0
1
0
Timer1 Clock Input
Timer1 Clock Input
Clear TMR3
Clear TMR3
Prescaler
Prescaler
1, 2, 4, 8
1, 2, 4, 8
The operating mode is determined by the clock select
bit, TMR3CS (T3CON<1>). When TMR3CS is cleared
(= 0), Timer3 increments on every internal instruction
cycle (F
on every rising edge of the Timer1 external clock input
or the Timer1 oscillator, if enabled.
As with Timer1, the RC1/T1OSI and RC0/T1OSO/
T13CKI pins become inputs when the Timer1 oscillator
is enabled. This means the values of TRISC<1:0> are
ignored and the pins are read as ‘0’.
2
2
OSC
TMR3L
TMR3L
/4). When the bit is set, Timer3 increments
8
Sleep Input
Sleep Input
8
Synchronize
Synchronize
Detect
Detect
High Byte
High Byte
TMR3H
TMR3
TMR3
8
 2004 Microchip Technology Inc.
8
8
Internal Data Bus
1
0
1
0
Read TMR1L
Write TMR1L
on Overflow
on Overflow
TMR3IF
TMR3IF
Set
Set
Timer3
Timer3
On/Off
On/Off