PIC16C711-04SS 데이터 시트보기 (PDF) - Microchip Technology

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PIC16C711-04SS

8-Bit CMOS Microcontrollers with A/D Converter

Microchip Technology 

6.3.1 SWITCHING PRESCALER ASSIGNMENT

The prescaler assignment is fully under software con-

trol, i.e., it can be changed “on the fly” during program

execution.

PIC16C71X

Note:

To avoid an unintended device RESET, the

following instruction sequence (shown in

Example 6-1) must be executed when

changing the prescaler assignment from

Timer0 to the WDT. This sequence must be

followed even if the WDT is disabled.

EXAMPLE 6-1: CHANGING PRESCALER (TIMER0→WDT)

BCF STATUS, RP0

CLRF TMR0

BSF STATUS, RP0

CLRWDT

MOVLW b'xxxx1xxx'

MOVWF OPTION_REG

BCF STATUS, RP0

;Bank 0

;Clear TMR0 & Prescaler

;Bank 1

;Clears WDT

;Selects new prescale value

;and assigns the prescaler to the WDT

;Bank 0

To change prescaler from the WDT to the Timer0

module use the sequence shown in Example 6-2.

EXAMPLE 6-2: CHANGING PRESCALER (WDT→TIMER0)

CLRWDT

BSF

MOVLW

MOVWF

BCF

;Clear WDT and prescaler

STATUS, RP0 ;Bank 1

b'xxxx0xxx' ;Select TMR0, new prescale value and

OPTION_REG ;clock source

STATUS, RP0 ;Bank 0

TABLE 6-1: REGISTERS ASSOCIATED WITH TIMER0

Address Name Bit 7 Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

Value on:

POR,

BOR

Value on all

other resets

01h

TMR0 Timer0 module’s register

xxxx xxxx uuuu uuuu

0Bh,8Bh, INTCON GIE ADIE

T0IE

INTE RBIE T0IF INTF RBIF 0000 000x 0000 000u

81h

OPTION RBPU INTEDG T0CS T0SE PSA PS2 PS1 PS0 1111 1111 1111 1111

85h

TRISA

—

—

— PORTA Data Direction Register

---1 1111 ---1 1111

Legend: x = unknown, u = unchanged, - = unimplemented locations read as '0'. Shaded cells are not used by Timer0.

© 1997 Microchip Technology Inc.

DS30272A-page 35

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