PIC16C72-02/SS Microchip Technology, PIC16C72-02/SS Datasheet - Page 69

• Manufacturer Part Number: PIC16C72-02/SS
• Description: 8-Bit CMOS Microcontrollers with A/D Converter
• Manufacturer: Microchip Technology

10.11
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 10-1 stores and restores the W and STATUS
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).
EXAMPLE 10-1: SAVING STATUS, W, AND PCLATH REGISTERS IN RAM
1998 Microchip Technology Inc.
MOVWF
SWAPF
CLRF
MOVWF
:
:Interrupt Service Routine (ISR) - user defined
:
SWAPF
MOVWF
SWAPF
SWAPF
Context Saving During Interrupts
W_TEMP
STATUS,W
STATUS
STATUS_TEMP
STATUS_TEMP,W
STATUS
W_TEMP,F
W_TEMP,W
;Copy W to W_TEMP register, could be bank one or zero
;Swap status to be saved into W
;bank 0, regardless of current bank, Clears IRP,RP1,RP0
;Save status to bank zero STATUS_TEMP register
;Swap STATUS_TEMP register into W
;(sets bank to original state)
;Move W into STATUS register
;Swap W_TEMP
;Swap W_TEMP into W
Preliminary
The example:
a)
b)
c)
d)
e)
Stores the W register.
Stores the STATUS register in bank 0.
Executes the ISR code.
Restores the STATUS register (and bank select
bit).
Restores the W register.
PIC16C72 Series
DS39016A-page 69