MEL PICBASIC Forum - I’m Running Out of CodeSpace, What Can I Do?

  • I’m Running Out of CodeSpace, What Can I Do?

    by
    Melanie
    Published on - 23rd April 2010 19:28  Number of Views: 12115  
    I’m Running Out of CodeSpace, What can I do?
    My progam is too slow - What can I do?

    Apart from the obvious and move to a faster PIC with more program memory, there’s a few little known tricks you can try.

    Bank0

    No, that's not a reference to how much money you've got left at the end of each month. It refers to locating all your most commonly used variables in Bank0. Why? It takes a PIC fewer machine instructions to access Bank0 RAM than it does to access RAM located further up the chain. Fewer instructions means RAM is accessed faster - You may even find a performance improvement in seriously intensive processing applications.

    You can force your variables into Bank0 by simply specifying Bank0 after your variables definition… here is a snip from a typical program…

    Code:
        ADCValue var Byte Bank0      ' Final value from ADC
    BeepTone var Word         ' Variable for Beep Period (half-cycle)
    BeepLength var Word         ' Number of Repitition Cycles to execute
    CounterA var Byte Bank0     ' General Purpose Byte Counter
    CounterB var Byte Bank0     ' General Purpose Byte Counter
    Counterc var Word Bank0     ' General Purpose Word Counter
    DataA var Byte Bank0        ' General Purpose Byte Variable
    DataB var Byte Bank0        ' General Purpose Byte Variable
    DataC var Word Bank0        ' General Purpose Word variable
    DataP var Byte [45]         ' Preset Data loaded from EEPROM
    DataW var Word [28]         ' Word Counters/Timers
    Display var Byte        ' Display Status Counter
    ErrorStatus var Word Bank0    ' System Error Status
    I2CAddress var Byte        ' I2C Bus Hardware Address
    IPRX var WORD            ' Status Byte Received from AUX IP CPU
    IPTX var WORD            ' Command Byte for Transmission to AUX IP CPU
    KeyBut var Byte Bank0        ' Keyboard Status
    MenuStatus var Byte Bank0    ' Current Set-Up Menu Field being Referenced
    Message var Byte Bank0        ' Message Reference for Display
    How much can I save?

    Well, this very much depends on your style of programming and your use of variables, but, typically on an 8K PIC (say 16F876, 16F877), creative use of Bank0 can free up between 1K and 2K… that’s up to 25% extra codespace for FREE. Next time you’re running out of space or end up plagued by ‘feature-creep’ try it.

    Melanie
    This article was originally published in forum thread: I’m Running Out of CodeSpace, What Can I Do? started by Melanie View original post