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26070Re: ROM Bootloader Issues

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  • joshbensadon
    Jun 2 8:27 PM
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      I didn't see that $800 SWTPC, I guess my search is limited to what's available to Canada. But that is closer to a fair price compared to $3,800. And that $3,800 machine is worth closer to $200 imho, since it's modified. I certainly wouldn't buy it, not even at $200.

      I'm currently looking for a PET 2001... they are some around but non available to Canada. sigh


      --- In midatlanticretro@yahoogroups.com, Kyle Owen <kylevowen@...> wrote:
      >
      > Yeah, that particular machine has been listed...over and over and over!
      > Which is no surprise, of course, judging by the price tag. I think it's
      > just a very heavily modified 6800. Too modified for most of the purists out
      > there, I guess. There was a 6800 that just recently sold for almost $800.
      > Item number 150817895881. That is more than I expected it to go for, in
      > fact, as maybe 6 months ago, a complete system sold for only $600 or so. I
      > guess they're getting more desirable.
      >
      > Kyle
      >
      > On Sat, Jun 2, 2012 at 9:12 PM, joshbensadon <no_reply@yahoogroups.com>wrote:
      >
      > > **
      > >
      > >
      > > Well, there you go, I guessed Z80 code... boy was I ever out in left
      > > field! I was thinking it was for your North Star.
      > >
      > > Hey, talking about SWTPC, there's one for sale on Ebay right now, but sale
      > > is not the word for it, they want near 4G's for it!
      > > It looks like it has three 3-1/2" drives on the right side?
      > > Can you explain that?
      > >
      > >
      > > --- In midatlanticretro@yahoogroups.com, Kyle Owen <kylevowen@> wrote:
      > > >
      > > > The code is 6800 (for my SWTPC 6800, in fact). I failed to include that
      > > in
      > > > my original email, duh! Sorry about that.
      > > >
      > > > PSHA will push the contents of accumulator A onto the stack and will then
      > > > decrease the SP by one. PULA will increase the SP by one and pull the
      > > byte
      > > > at the SP into accumulator A. Yeah, I got confused somewhere in there.
      > > >
      > > > DEX in the 6800 will only affect the zero flag, no others. I'm quite sure
      > > > of that. The other decrement operands (DEC, DECA, DECB) will affect the
      > > > negative, zero and overflow flags, however.
      > > >
      > > > My latest (working, even!) version is indeed using CPX. In fact, here's
      > > the
      > > > code: http://pastebin.com/VQFsPFqH
      > > >
      > > > 73,
      > > >
      > > > Kyle
      > > >
      > > > On Sat, Jun 2, 2012 at 7:06 PM, joshbensadon <no_reply@yahoogroups.com
      > > >wrote:
      > > >
      > > > > **
      > >
      > > > >
      > > > >
      > > > > Hi Kyle,
      > > > >
      > > > > I might be a little confused so excuse me if I'm in left field.
      > > > >
      > > > > Looking at your code, it looks like Z80 right?
      > > > > Doesn't the PUSH put 2 bytes on the stack? Accumulator and PSW??
      > > > > Further, the PUSH decrements the places the data.
      > > > > So, you should load the stack pointer with RAMEND+1 and after every
      > > push,
      > > > > you should INX SP.
      > > > >
      > > > >
      > > > > --- 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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