PIC18FXX20
14.0
TIMER3 MODULE
The Timer3 module timer/counter has the following
features:
• 16-bit timer/counter
(two 8-bit registers; TMR3H and TMR3L)
• Readable and writable (both registers)
• Internal or external clock select
• Interrupt-on-overflow from FFFFh to 0000h
• RESET from CCP module trigger
module.
register controls the Operating mode of the Timer3
module and sets the CCP clock source.
register controls the Operating mode of the Timer1
module, as well as contains the Timer1 oscillator
enable bit (T1OSCEN), which can be a clock source for
Timer3.
REGISTER 14-1:
T3CON: TIMER3 CONTROL REGISTER
R/W-0
RD16
bit 7
R/W-0
T3CCP2
R/W-0
T3CKPS1
R/W-0
T3CKPS0
R/W-0
T3CCP1
R/W-0
T3SYNC
R/W-0
TMR3CS
R/W-0
TMR3ON
bit 0
bit 7
RD16:
16-bit Read/Write Mode Enable bit
1
= Enables register Read/Write of Timer3 in one 16-bit operation
0
= Enables register Read/Write of Timer3 in two 8-bit operations
T3CCP2:T3CCP1:
Timer3 and Timer1 to CCPx Enable bits
11
= Timer3 and Timer4 are the clock sources for CCP1 through CCP5
10
= Timer3 and Timer4 are the clock sources for CCP3 through CCP5;
Timer1 and Timer2 are the clock sources for CCP1 and CCP2
01
= Timer3 and Timer4 are the clock sources for CCP2 through CCP5;
Timer1 and Timer2 are the clock sources for CCP1
00
= Timer1 and Timer2 are the clock sources for CCP1 through CCP5
T3CKPS1:T3CKPS0:
Timer3 Input Clock Prescale Select bits
11
= 1:8 Prescale value
10
= 1:4 Prescale value
01
= 1:2 Prescale value
00
= 1:1 Prescale value
T3SYNC:
Timer3 External Clock Input Synchronization Control bit
(Not usable if the system clock comes from Timer1/Timer3.)
When TMR3CS =
1:
1
= Do not synchronize external clock input
0
= Synchronize external clock input
When TMR3CS =
0:
This bit is ignored. Timer3 uses the internal clock when TMR3CS =
0.
TMR3CS:
Timer3 Clock Source Select bit
1
= External clock input from Timer1 oscillator or T13CKI
(on the rising edge after the first falling edge)
0
= Internal clock (F
OSC
/4)
TMR3ON:
Timer3 On bit
1
= Enables Timer3
0
= Stops Timer3
Legend:
R = Readable bit
- n = Value at POR
W = Writable bit
‘1’ = Bit is set
U = Unimplemented bit, read as ‘0’
‘0’ = Bit is cleared
x = Bit is unknown
bit 6,3
bit 5-4
bit 2
bit 1
bit 0
2003 Microchip Technology Inc.
Advance Information
DS39609A-page 143
MICROCHIP [ MICROCHIP TECHNOLOGY ]
