Microchip Technology MCP1630DM-DDBS1 Data Sheet

©

 2007 Microchip Technology Inc.

DS41211D-page 95

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 lower 16 bytes of all banks are common in the
PIC12F683 (see Figure 2-2), temporary holding regis-
ters, W_TEMP and STATUS_TEMP, should be placed
in here. These 16 locations do not require banking and
therefore, makes it easier to context save and restore.
The same code shown in Example 12-1 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 PIC12F683 normally does not require
saving the PCLATH. However, if com-
puted 

GOTO

’s 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