PIC16LC925T-I/CL 查看數據表（PDF） - Microchip Technology

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PIC16LC925T-I/CL

64/68-Pin CMOS Microcontrollers with LCD Driver

Microchip Technology 

PIC16C925/926

12.6 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., the W and STATUS reg-

isters. This will have to be implemented in software.

Example 12-1 stores and restores the STATUS, W, and

PCLATH registers. The register, W_TEMP, must be

defined in each bank and must be defined at the same

offset from the bank base address (i.e., if W_TEMP is

defined at 0x20 in bank 0, it must also be defined at

0xA0 in bank 1).

The code in the example:

e) Stores the W register.

f) Stores the STATUS register in bank 0.

g) Stores the PCLATH register.

h) Executes the ISR code.

i) Restores the STATUS register (and bank select

bit).

j) Restores the W and PCLATH registers.

EXAMPLE 12-1: SAVING STATUS, W, AND PCLATH 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

CLRF

STATUS

;bank 0, regardless of current bank, Clears IRP,RP1,RP0

MOVWF STATUS_TEMP

;Save status to bank zero STATUS_TEMP register

MOVF

PCLATH, W

;Only required if using pages 1, 2 and/or 3

MOVWF PCLATH_TEMP

;Save PCLATH into W

CLRF

PCLATH

;Page zero, regardless of current page

BCF

STATUS, IRP

;Return to Bank 0

MOVF

FSR, W

;Copy FSR to W

MOVWF FSR_TEMP

;Copy FSR from W to FSR_TEMP

:

:(ISR)

;Insert user code here

:

MOVF

PCLATH_TEMP, W ;Restore PCLATH

MOVWF PCLATH

;Move W into PCLATH

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

 2001 Microchip Technology Inc.

Preliminary

DS39544A-page 109

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