PIC16F84A-10SLASHSS datasheet(31/124 Pages) MICROCHIP

31 / 124 page

PIC16F8X

DS30430C-page 31

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).

EXAMPLE 6-1:

CHANGING PRESCALER

(TIMER0

→WDT)

BCF

STATUS, RP0

;Bank 0

CLRF

TMR0

;Clear TMR0

; and Prescaler

BSF

STATUS, RP0

;Bank 1

CLRWDT

;Clears WDT

MOVLW

b'xxxx1xxx'

;Select new

MOVWF

OPTION_REG

; prescale value

BCF

STATUS, RP0

;Bank 0

EXAMPLE 6-2:

CHANGING PRESCALER

(WDT

→TIMER0)

CLRWDT

;Clear WDT and

; prescaler

BSF

STATUS, RP0

;Bank 1

MOVLW

b'xxxx0xxx'

;Select TMR0, new

; prescale value

’ and clock source

MOVWF

OPTION_REG

;

BCF

STATUS, RP0

;Bank 0

TABLE 6-1

REGISTERS ASSOCIATED WITH TIMER0

Note:

To avoid an unintended device RESET, the

following

instruction

sequence

(Example 6-1) must be executed when

changing the prescaler assignment from

Timer0 to the WDT. This sequence must

be taken even if the WDT is disabled. To

change prescaler from the WDT to the

Timer0 module use the sequence shown in

Example 6-2.

Address

Name

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

Value on

Power-on

Reset

Value on all

other resets

01h

TMR0

Timer0 module’s register

xxxx xxxx

uuuu uuuu

0Bh

INTCON

GIE

EEIE

T0IE

INTE

RBIE

T0IF

INTF

RBIF

0000 000x

0000 0000

81h

OPTION_

REG

RBPU

INTEDG

T0CS

T0SE

PSA

PS2

PS1

PS0

1111 1111

85h

TRISA

—

TRISA4

TRISA3

TRISA2

TRISA1

TRISA0

---1 1111

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

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