Microchip Technology MCP1631RD-MCC2 Data Sheet

 2006-2012 Microchip Technology Inc.

DS41291G-page 227

During an interrupt, only the return PC value is saved
on the stack. Typically, users may wish to save key
registers during an interrupt (e.g., W and STATUS
registers). This must be implemented in software.
Since the upper 16 bytes of all GPR banks are
common in the PIC16F882/883/884/886/887 (see
Figures

 and 

), temporary holding registers,

W_TEMP and STATUS_TEMP, should be placed in
here. These 16 locations do not require banking and
therefore, make it easier to context save and restore.
The same code shown in 

 can be used

to:
• Store the W register
• Store the STATUS register
• Execute the ISR code
• Restore the Status (and Bank Select Bit register)
• Restore the W register

The PIC16F882/883/884/886/887 devices
normally do not require saving the
PCLATH. However, if computed GOTOs
are used in the ISR and the main code,
the PCLATH must be saved and restored
in the ISR.

MOVWF W_TEMP

;Copy W to TEMP register

SWAPF STATUS,W

;Swap status to be saved into W 
;Swaps are used because they do not affect the status bits

MOVWF STATUS_TEMP

;Save status to bank zero STATUS_TEMP register

:
:(ISR)

;Insert user code here

:
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