Datasheet

 1998-2013 Microchip Technology Inc. DS30289C-page 41
PIC17C7XX
EXAMPLE 6-1: SAVING STATUS AND WREG IN RAM (SIMPLE)
; The addresses that are used to store the CPUSTA and WREG values must be in the data memory
; address range of 1Ah - 1Fh. Up to 6 locations can be saved and restored using the MOVFP
; instruction. This instruction neither affects the status bits, nor corrupts the WREG register.
;
UNBANK1 EQU 0x01A ; Address for 1st location to save
UNBANK2 EQU 0x01B ; Address for 2nd location to save
UNBANK3 EQU 0x01C ; Address for 3rd location to save
UNBANK4 EQU 0x01D ; Address for 4th location to save
UNBANK5 EQU 0x01E ; Address for 5th location to save
; (Label Not used in program)
UNBANK6 EQU 0x01F ; Address for 6th location to save
; (Label Not used in program)
;
: ; At Interrupt Vector Address
PUSH MOVFP ALUSTA, UNBANK1 ; Push ALUSTA value
MOVFP BSR, UNBANK2 ; Push BSR value
MOVFP WREG, UNBANK3 ; Push WREG value
MOVFP PCLATH, UNBANK4 ; Push PCLATH value
;
: ; Interrupt Service Routine (ISR) code
;
POP MOVFP UNBANK4, PCLATH ; Restore PCLATH value
MOVFP UNBANK3, WREG ; Restore WREG value
MOVFP UNBANK2, BSR ; Restore BSR value
MOVFP UNBANK1, ALUSTA ; Restore ALUSTA value
;
RETFIE ; Return from interrupt (enable interrupts)