Indirectly accessing the access bank (18F)

[pittuck]

Hi need some ASM help

Ok i am just working on some code [and i realise the W and other registers have not been saved yet, do that later, perhaps after i get some breaky, anyhow.

isr

    ; Handle Interupts
    BTFSC PIR1, RCIF            ; If RCIF Set GOTO Debug
    GOTO Debug
    GOTO Int_Exit
    
    Debug
        
        CALL Getc               ; Get The Command
        MOVWF debug_command
        
        MOVLW 0x7A
        CALL Putc               ; Send We are here
        
        if debug_command == 0x01   ; Its a debug command
            CALL Getc           ; Get The Data
            MOVWF debug_data
            
            ***
            CALL Putc
        endif
        
    GOTO Int_Exit

Int_Exit

RETFIE

Basically i send a command over RS232, wait for a reply, then send another byte, in this case a memory address which points to a location in the access bank. what i want to do is put the value of the data at the address stored in debug_data to W so it can be sent back to the PC.

Any ideas? I think there was something in elektor a few months ago, i will search my room for it now, but neone have any ideas?

 

[pittuck]

Ok, elektor had the answer here is the code for the ISR now, just to show how its done.

isr

    MOVWF W_TEMP                ; W_TEMP is in virtual bank
    MOVFF STATUS, STATUS_TEMP   ; STATUS_TEMP located anywhere
    MOVFF BSR, BSR_TEMP         ; BSR located anywhere

    ; Handle Interupts
    BTFSC PIR1, RCIF            ; If RCIF Set GOTO Debug
    GOTO Debug
    GOTO Int_Exit
    
    Debug
        
        CALL Getc               ; Get The Command
        MOVWF debug_command
        
        MOVLW 0x7A
        CALL Putc               ; Send We are here
        
                                ; Its a debug command
        if debug_command == 0x01
            CALL Getc           ; Get The Data
            MOVWF debug_data
            
            if debug_data <= 0x7F
                MOVLF FSR0H, 0x00
            else
                MOVLF FSR0H, 0x0F
            endif
            
            MOVF debug_data, FSR0L
            MOFF INDF0, W
            CALL Putc
        endif
        
    GOTO Int_Exit

    Int_Exit

    MOVFF BSR_TEMP, BSR         ; Restore BSR
    MOVF W_TEMP, W              ; Restore WREG
    MOVFF STATUS_TEMP,STATUS    ; Restore STATUS

RETFIE

Erm, well there is a 12 bit address for all of the RAM, the lower 128 are the lower access register, and the upper 128bytes are the upper access register (and are also the SFR). (giving a nice 128bytes of RAM, access to all SFR's and no bank switching needed, unless u use the other banks of course...)

Anyhow, the lower 8 bits of the 12 bit address goto FSR0L and the upper 4 goto the FSR0H, then u can read / write to the register INDF0.

lol, easy really.