Need Help with Assembly

This is a discussion on Need Help with Assembly within the Tech Board forums, part of the Community Boards category; This program is supposed to count the number of letters in a string Code: ORG RAMStart String DC.B "This is ...

  1. #1
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    Need Help with Assembly

    This program is supposed to count the number of letters in a string

    Code:
                ORG RAMStart
    
    String      DC.B  "This is a test string",0
    Size         DS.B  1      
          
          
    
    
    ; code section
                ORG   ROMStart
    Entry:
                        
      LDX        #String
      LDAA      #0
      
    loop:   
      LDAA      0,x
      inc          Size
      inx
      bne       loop
      bra       *
    I figured when the null character was loaded into accumulator A that it would end the loop, but it keeps counting the size. Any ideas as to how to solve this. Also, is there a board similar to this for assembly? Thanks

  2. #2
    and the hat of int overfl Salem's Avatar
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    Not a C question, moved.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
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    Well why don't you make an assembly sub forum. No one reads this Tech board apparently.

  4. #4
    and the hat of int overfl Salem's Avatar
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    Because this is C programming.com.
    We don't have asm for the same reason we don't have pascal, cobol or fortran sub-sections either.

    Try daniweb, they have an asm forum there.
    If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.
    If at first you don't succeed, try writing your phone number on the exam paper.
    I support http://www.ukip.org/ as the first necessary step to a free Europe.

  5. #5
    Banned master5001's Avatar
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    Well first of all, its not my fault that people use similar titled threads in the Tech forum and you just assume its the same old answered question.

    Secondly, I am only familiar enough with SPARC assembler to identify it. So excuse me for only knowing how to write assembler for a modern piece of hardware.

  6. #6
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    You need a BEQ (and possibly a compare with zero - I don't know the assembler well enough, but most assembler languages will set the zero flag ) after you load the character from the string into AA. AA is overwritten as soon as you load the first character from the string, so storing zero in it will not make any difference.

    [I have no idea which processor this is for - perhaps one of those funny 6502-extensions that Hitachi have been making for quite a few years, e.g. HC11 or HC12]

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  7. #7
    Banned master5001's Avatar
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    Most assemblers offer an opcode that jumps only when the zero flag is set. For SPARC assembler I believe "bz" is the appropriate opcode. So swap out your bne with bz and increment the original string pointer and check its value against zero.

  8. #8
    Malum in se abachler's Avatar
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    BNE and BZ are nto the same thing. BNE is BNZ. BZ is BE or BEQ depending ont eh assembler used..
    Until you can build a working general purpose reprogrammable computer out of basic components from radio shack, you are not fit to call yourself a programmer in my presence. This is cwhizard, signing off.

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    Banned master5001's Avatar
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    If I am not mistaken, BNE is Branch if Not Equal. So your loop will exhibit funky behavior...

  10. #10
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    Quote Originally Posted by master5001 View Post
    If I am not mistaken, BNE is Branch if Not Equal. So your loop will exhibit funky behavior...
    I'm sure that a BNE in that place would be perfectly fine _IF_ the Z flag was set by the LDAA, but it's (probably) also set by both of the next two instructions.

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    Please don't PM me for help - and no, I don't do help over instant messengers.

  11. #11
    Banned master5001's Avatar
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    It don't think INX will change the z flag. But I am not sure. INC definitely should modify the z flag. I would still have the last thing done proir to jumping be to do a comparison. That is a more conventional way of doing this sort of thing.

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