PIC18LF4331 datasheet(131/392 Pages) MICROCHIP

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 2010 Microchip Technology Inc.

DS39616D-page 131

PIC18F2331/2431/4331/4431

13.0

TIMER1 MODULE

The Timer1 timer/counter module has the following

features:

• 16-bit timer/counter

(two 8-bit registers; TMR1H and TMR1L)

• Readable and writable (both registers)

• Internal or external clock select

• Interrupt-on-overflow from FFFFh to 0000h

• Reset from CCP module Special Event Trigger

• Status of system clock operation

Figure 13-1 is a simplified block diagram of the Timer1

module.

module and contains the Timer1 Oscillator Enable bit

(T1OSCEN). Timer1 can be enabled or disabled by

setting or clearing control bit, TMR1ON (T1CON<0>).

The Timer1 oscillator can be used as a secondary clock

source in power-managed modes. When the T1RUN

bit is set, the Timer1 oscillator provides the system

clock. If the Fail-Safe Clock Monitor is enabled and the

Timer1 oscillator fails while providing the system clock,

polling the T1RUN bit will indicate whether the clock is

being provided by the Timer1 oscillator or another

source.

Timer1 can also be used to provide Real-Time Clock

(RTC) functionality to applications with only a minimal

addition of external components and code overhead.

T1CON: TIMER1 CONTROL REGISTER

R/W-0

R-0

R/W-0

RD16

T1RUN

T1CKPS1

T1CKPS0

T1OSCEN

T1SYNC

TMR1CS

TMR1ON

bit 7

bit 0

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

bit 7

RD16:

16-Bit Read/Write Mode Enable bit

= Enables register read/write of TImer1 in one 16-bit operation

= Enables register read/write of Timer1 in two 8-bit operations

bit 6

T1RUN:

Timer1 System Clock Status bit

= Device clock is derived from Timer1 oscillator

= Device clock is derived from another source

bit 5-4

T1CKPS<1:0>:

Timer1 Input Clock Prescale Select bits

= 1:8 Prescale value

= 1:4 Prescale value

= 1:2 Prescale value

= 1:1 Prescale value

bit 3

T1OSCEN:

Timer1 Oscillator Enable bit

= Timer1 oscillator is enabled

= Timer1 oscillator is shut off

The oscillator inverter and feedback resistor are turned off to eliminate power drain.

bit 2

T1SYNC:

Timer1 External Clock Input Synchronization Select bit

When TMR1CS = 1 (External Clock):

= Do not synchronize external clock input

= Synchronize external clock input

When TMR1CS = 0 (Internal Clock):

This bit is ignored. Timer1 uses the internal clock when TMR1CS = 0.

bit 1

TMR1CS:

Timer1 Clock Source Select bit

= External clock from pin RC0/T1OSO/T1CKI (on the rising edge)

= Internal clock (FOSC/4)

bit 0

TMR1ON:

Timer1 On bit

= Enables Timer1

=Stops Timer1

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