Interrupts - again

[Charles Linquis]

I have been going back and forth through the various assembly-language interrupt routines for PBP, but I keep getting confused.

I'm using 18F parts. Can anyone tell me exactly which registers I must save and restore when writing an ISR that is entirely in assembly?

STATUS, W?
STATUS, W, PCLATH, FSR0? More?

[SteveB]

Charles,
You only need to save the value of registers that your ISR may change. The datasheet for the 18F series has an example for what would be considered as a bare minimum:

MOVWF  W_TEMP                        ; W_TEMP is in virtual bank
MOVFF  STATUS, STATUS_TEMP    ; STATUS_TEMP located anywhere
MOVFF  BSR, BSR_TEMP                ; BSR_TMEP located anywhere
;
; USER ISR CODE
;
MOVFF  BSR_TEMP, BSR                ; Restore BSR
MOVF   W_TEMP, W                     ; Restore WREG
MOVFF  STATUS_TEMP, STATUS    ; Restore STATUS

You may also need to save the PCL related registers and any FSRs you intend to use. So...

Can anyone tell me exactly which registers I must save and restore when writing an ISR that is entirely in assembly?

No. Unless, of course, you posted your code. However, your question may be more appropriate on the Microchip forum vs. the PIC BASIC pro forum. You may even find your answer there with a little searching.

Steve