18F8680 datasheet(166/496 Pages) MICROCHIP

166 / 496 page

PIC18F6585/8585/6680/8680

DS30491C-page 164

 2004 Microchip Technology Inc.

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

Figure 14-1 is a simplified block diagram of the Timer3

module.

module and sets the Enhanced CCP1 and CCP2 clock

source.

module, as well as containing the Timer1 oscillator

enable bit (T1OSCEN) which can be a clock source for

Timer3.

T3CON: TIMER3 CONTROL REGISTER

R/W-0

RD16

T3CCP2

T3CKPS1

T3CKPS0

T3CCP1

T3SYNC

TMR3CS

TMR3ON

bit 7

bit 0

bit 7

RD16: 16-bit Read/Write Mode Enable bit

= Enables register read/write of Timer3 in one 16-bit operation

= Enables register read/write of Timer3 in two 8-bit operations

bit 6, 3

T3CCP2:T3CCP1: Timer3 and Timer1 to CCPx Enable bits

= Timer3 is the clock source for compare/capture of CCP1 and CCP2 modules

= Timer3 is the clock source for compare/capture of CCP2 module,

Timer1 is the clock source for compare/capture of CCP1 module

= Timer1 is the clock source for compare/capture of CCP1 and CCP2 modules

bit 5-4

T3CKPS1:T3CKPS0: Timer3 Input Clock Prescale Select bits

= 1:8 prescale value

= 1:4 prescale value

= 1:2 prescale value

= 1:1 prescale value

bit 2

T3SYNC: Timer3 External Clock Input Synchronization Control bit

(Not usable if the system clock comes from Timer1/Timer3.)

When TMR3CS = 1:

= Do not synchronize external clock input

= Synchronize external clock input

When TMR3CS = 0:

This bit is ignored. Timer3 uses the internal clock when TMR3CS = 0.

bit 1

TMR3CS: Timer3 Clock Source Select bit

= External clock input from Timer1 oscillator or T13CKI

(on the rising edge after the first falling edge)

= Internal clock (FOSC/4)

bit 0

TMR3ON: Timer3 On bit

= Enables Timer3

= Stops Timer3

Legend:

R = Readable bit

W = Writable bit

U = Unimplemented bit, read as ‘0’

- n = Value at POR

‘1’ = Bit is set

‘0’ = Bit is cleared

x = Bit is unknown

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