PIC14000 datasheet(84/153 Pages) MICROCHIP

84 / 153 page

PIC14000

DS40122B-page 84

Preliminary

10.6.2

TIMER0 INTERRUPT

An overﬂow (FFh

→ 00h) in Timer0 will set the T0IF

(INTCON<2>)

ﬂag.

Setting

T0IE

(INTCON<5>)

enables the interrupt.

10.6.3

PORTC INTERRUPT ON CHANGE

input

change

PORTC<7:4>

sets

RCIF

(PIR1<2>). Setting RCIE (PIE1<2>) enables the inter-

rupt. For operation of PORTC, refer to Section 5.2.

Note:

If a change on the I/O pin should occur

when the read operation is being executed

(start of the Q2 cycle), then the RCIF

interrupt ﬂag may not be set.

10.6.4

CONTEXT SWITCHING DURING

INTERRUPTS

During an interrupt, only the return PC value is saved

on the stack. Typically, users may wish to save key

registers during an interrupt, for example, W register

and Status register. Example 10-1 is an example that

shows saving registers in RAM.

EXAMPLE 10-1: SAVING STATUS AND W REGISTERS IN RAM

MOVWF

W_TEMP

;Copy W to TEMP register, could be any bank

SWAPF

STATUS,W

;Swap status to be saved into W

BCF

STATUS,RP1

;Change to bank zero, regardless of current bank

BCF

STATUS,RP0

;

MOVWF

STATUS_TEMP

;Save status to bank zero STATUS_TEMP register

:(ISR)

SWAPF

STATUS_TEMP,W

;Swap STATUS_TEMP register into W

;(sets bank to original state)

MOVWF

STATUS

;Move W into STATUS register

SWAPF

W_TEMP,F

;Swap W_TEMP

SWAPF

W_TEMP,W

;Swap W_TEMP into W

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