PIC16C781 datasheet(57/186 Pages) MICROCHIP

57 / 186 page

 2001 Microchip Technology Inc.

Preliminary

DS41171A-page 55

PIC16C781/782

6.0

TIMER1 MODULE WITH GATE

CONTROL

The Timer1 module timer/counter 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

• External enable input (T1G pin with TMR1GE bit = 1)

• Option for Timer1 to use LP oscillator if device is

configured to use INTRC w/o CLKOUT

Timer1 Control register (T1CON) is shown in Register 6-1.

Figure 6-2 is a simplified block diagram of the Timer1

module.

6.1

Timer1 Operation

Timer1 can operate in one of three modes:

16-bit timer with prescaler.

16-bit synchronous counter.

16-bit asynchronous counter.

In Timer mode, Timer1 is incremented on every instruc-

tion cycle. In Counter mode, Timer1 is incremented on

the rising edge of the external clock input T1CKI (RA6/

OSC2/CLKOUT/T1CKI). In addition, the Counter mode

clock can be synchronized to the microcontroller clock

or run asynchronously.

In Counter and Timer modes, the counter/timer clock

can be gated by the T1G input.

If an external clock oscillator is needed (and the micro-

controller is using INTRC w/o CLKOUT), Timer1 can

use the LP oscillator as a clock source.

EXAMPLE 6-1:

TIMER1 INITIALIZATION

;* This code block will configure Timer1 for

;* Polling, Ext gate of int clk (Fosc/4), &

;* 1:1 prescaler.

;* Wait for TMR1 overflow code included

BANKSEL

TMR1L

; Select Bank 0

CLRF

TMR1L

; Clear TMR1 LSB

CLRF

TMR1H

; Clear TMR1 MSB

MOVLW

B’01000000’

; Gate, Ps 1:1

MOVWF

T1CON

; Int clk

BSF

T1CON,TMR1ON

; Enable timer

;********************************************

;* Wait for TMR1 overflow

T1_OVFL_WAIT

BANKSEL

PIR1

; Select Bank 0

T1_WAIT

;

TBFSS

PIR1,TMR1IF

; Overflow?

GOTO

T1_WAIT

; If 0, again

BCF

PIR1,TMR1IF

; Clear flag

Note 1: In Counter mode, the counter increments

on the rising edge of the clock.

PIC16C781 Datasheet(PDF) 57 Page - Microchip Technology

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