PIC16C62XAT-20I/SO View Datasheet(PDF) - Microchip Technology

Part Name

Description

Manufacturer

PIC16C62XAT-20I/SO

EPROM-Based 8-Bit CMOS Microcontroller

Microchip Technology 

PIC16C62X

6.3.1 SWITCHING PRESCALER ASSIGNMENT

The prescaler assignment is fully under software

control (i.e., it can be changed “on the fly” during

program execution). To avoid an unintended device

RESET, the following instruction sequence

(Example 6-1) must be executed when changing the

prescaler assignment from Timer0 to WDT.

EXAMPLE 6-1: CHANGING PRESCALER

(TIMER0→WDT)

1.BCF STATUS, RP0 ;Skip if already in

; Bank 0

2.CLRWDT

;Clear WDT

3.CLRF TMR0

;Clear TMR0 & Prescaler

4.BSF STATUS, RP0 ;Bank 1

5.MOVLW '00101111’b; ;These 3 lines (5, 6, 7)

6.MOVWF OPTION

; are required only if

; desired PS<2:0> are

7.CLRWDT

; 000 or 001

8.MOVLW '00101xxx’b ;Set Postscaler to

9.MOVWF OPTION

; desired WDT rate

10.BCF STATUS, RP0 ;Return to Bank 0

To change prescaler from the WDT to the TMR0

module use the sequence shown in Example 6-2. This

precaution must be taken even if the WDT is disabled.

EXAMPLE 6-2: CHANGING PRESCALER

(WDT→TIMER0)

CLRWDT

BSF

MOVLW

MOVWF

BCF

STATUS, RP0

b'xxxx0xxx'

OPTION_REG

STATUS, RP0

;Clear WDT and

;prescaler

;Select TMR0, new

;prescale value and

;clock source

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

Value on

All Other

Resets

01h

TMR0 Timer0 module register

xxxx xxxx uuuu uuuu

0Bh/8Bh INTCON GIE PEIE 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

—

—

— TRISA4 TRISA3 TRISA2 TRISA1 TRISA0 ---1 1111 ---1 1111

Legend: — = Unimplemented locations, read as ‘0’.

Note:

Shaded bits are not used by TMR0 module.

u = unchanged

x = unknown

© 1998 Microchip Technology Inc.

Preliminary

DS30235G-page 35

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