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26062Re: ROM Bootloader Issues

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  • joshbensadon
    Jun 2, 2012
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      Kyle, oh, I don't think DEX affects the flags...

      --- In midatlanticretro@yahoogroups.com, Kyle Owen <kylevowen@...> wrote:
      >
      > Hi guys,
      >
      > So I recently copied 8k BASIC to (4) 2kB EEPROMs in hopes that I could make
      > a bootloader to copy the contents into RAM, eliminating the 5 minutes or so
      > that it would otherwise take to load BASIC via RS-232.
      >
      > Anyways, I'm completely stumped as to why my very simple bootloader isn't
      > working correctly. The code can be found here: http://pastebin.com/jbrTHdnX
      >
      > It actually does copy the contents correctly, but fails to exit to the
      > monitor on time. The DEX instruction can only update the zero flag, so I am
      > fairly limited on branches. It should exit the loop as soon as the index
      > register is zero, but instead, it exits well after the index register
      > underflows.
      >
      > Any help would be much appreciated, as always. Thanks!
      >
      > Kyle
      >
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