PIC16C71T-04/SP 查看數據表（PDF） - Microchip Technology

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PIC16C71T-04/SP

8-Bit CMOS Microcontrollers with A/D Converter

Microchip Technology 

PIC16C71X

8.6 Context Saving During Interrupts

During an interrupt, only the return PC value is saved

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

isters during an interrupt i.e., W register and STATUS

register. This will have to be implemented in software.

Example 8-1 stores and restores the STATUS and W

registers. The user register, STATUS_TEMP, must be

defined in bank 0.

The example:

a) Stores the W register.

b) Stores the STATUS register in bank 0.

c) Executes the ISR code.

d) Restores the STATUS register (and bank select

bit).

e) Restores the W register.

EXAMPLE 8-1: SAVING STATUS AND W REGISTERS IN RAM

MOVWF W_TEMP

;Copy W to TEMP register, could be bank one or zero

SWAPF STATUS,W

;Swap status to be saved into W

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

DS30272A-page 64

© 1997 Microchip Technology Inc.

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