Loading ...
Sorry, an error occurred while loading the content.

26064Re: ROM Bootloader Issues

Expand Messages
  • joshbensadon
    Jun 2, 2012
    • 0 Attachment
      Kyle, come to think of it, I think there's a CPX instruction to compare X with immediate, so you can affect the flags.

      --- In midatlanticretro@yahoogroups.com, joshbensadon <no_reply@...> wrote:
      >
      > 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
      > >
      >
    • Show all 9 messages in this topic