Accessing MultiByte Variables in Assembler


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  1. #1
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    Default Accessing MultiByte Variables in Assembler

    This may have been covered elsewhere, but I'm having trouble figuring out how to access the High and Low Bytes of 16-bit Words in Assembler. I know I can point the FSR register at the _Variable to get the Low byte, add one, and get the High byte, but I was wondering if there was an easier more straightforward way.

    Also, I'm using the PM assembler, and I'm wondering if there is an equivalent for banksel?

  2. #2
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    Code:
    MYVAR      VAR WORD
    
    MYVAR_L   VAR MYVAR.lowbyte
    MYVAR_H   VAR MYVAR.highbyte
    
    
    ASM
    
    CLRF    _MYVAR_L
    CLRF    _MYVAR_H
    
    ENDASM
    YOU CAN USE THIS. I USE THIS METHODE WITH LONG VARIABLES. THERE IS NO PROBLEM.

  3. #3
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    Default Thanks!

    Thank you very much! I'm surprised I didn't think of that.
    Now comes the next question.
    Is there a "banksel" function equivalent in PM assembler?

  4. #4
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    Code:
    Is there a "banksel" function equivalent in PM assembler?
    NO THERE ISNT ANY EQUIVALENT FUNCTION.

    I KNOW THAT , PIC BASIC PRO MAKES THE BANKSEL FUNCTION ITSELF.

  5. #5
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    Default Hmm....

    I'm trying to use inline Assembler, but I use multiple arrays which means I need to address multiple banks. How can I tell which bank a given array is stored in?
    Also, I'm not certain how you mean that banksel is produced by PM itself. I'm using 2.5, and it's choking on errors - all related to my attempts to use banksel.

    This may all be simplified if I just specify which bank I want each variable in.

  6. #6
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    Quote Originally Posted by The Altruist
    I'm having trouble figuring out how to access the High and Low Bytes of 16-bit Words in Assembler.
    Code:
    MyWord  VAR WORD BANK0
    
    ASM
        movf     _MyWord,w      ; this gets the LowByte
        movwf    PORTB
    
        movf     _MyWord + 1,w  ; this gets the HighByte
        movwf    PORTC
    ENDASM
    You can use the CHK?RP macro to locate the bank for any variable.
    But if you're accessing arrays, it's probably better to use an FSR/INDF.
    <br>
    DT

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