PDA ramblings...

Ian Molton spyro at f2s.com
Thu Feb 6 18:54:33 PST 2003

On Fri, 7 Feb 2003 02:23:10 +0000 (UTC)
matt at matt.rogers.name (Matt Rogers) wrote:

> On Thursday 06 February 2003 08:11 pm, you wrote:
> > Well, I've spent two hours when I should have been sleeping tonight
> > to reverse engineer more of the bootloader...
> >
> > I have a partial map of the call structure of the bootloader, and
> > where its data is (attached below for the curious).

> hehe, i'm curious :)

> > I have identified what code I can, except that I got tired, so much
> > is labeled 'code' and 'data'. Eventually, all of the code will be
> > traced so I can see the call sequence.
> >
> > I can identify a lot of the code by the locations in memory that it
> > accesses, as I have a document with the memory map of a PXA250
> > microporcessor. this will make identifying MMU, CF, SD, IR, and
> > other IO code easy, although it wont help me see WHAT the code is up
> > to...
> >
> Ok, I think i know what SD and IR stand for. Enlighten those of us who
> don't know what MMU or CF stand for. (We're not worthy!!!!! :) )

Memory Management Unit and CompactFlash ;-) (SD = SecureDigital IR is my
shorthand for IrDA).

> > Tomorrow, I will see if I can finish at least the map, and hopefully
> > the call-tree as well.
> >
> I wish I had that much time on my hands. Stupid school stuff :(

I wish I was like the Dr. on Enterprise. (ie. hibernatory). I hate
having to actually /sleep/.

> > All I can say is... THANK GOD that 3/4 of the 256KB is image data!
> > this is a LONG slow plod.
> Image data? what kind of image data? (hehe, i'm thinking logos and
> stupid shit like that, even though that's probably not at all what it
> is)

Well, theres about 64K of data which is an 8 bit paletted image (16 bpp
palette), displayed when the bootloader runs. the rest is presently a
mystery. It may simply be garbage. the bootloader code copies only the
first 256KB into RAM, so I know it isnt bigger than that. It could be
smaller though.

> > Im going to be pda-less for a couple of days, since it needs to
> > return to toshiba for minor repairs (audio recording 'clicks' and
> > the wireless switch is broken, bah!). when I get it back, hopefully
> > I will have some code to try on it ;-)
> Only a couple of days? Now that's what I call service! Nice! (Let's
> hope it doesn't turn into weeks)

I hope so. It was a battle to get them to look at it at all, since it
was bought in canada, not the UK (stupid, since its EXACTLY the same
> > Oh, and I have found a local company that will do SMT rework of mBGA
> > chips... Im going to buy a PXA255 (faster CPU, basically a PXA250
> > without the bugs in its cache) and get it fitted. I will then have
> > the fastest XScale PDA in the world (and the difference is NOT small
> > - over 4X the memory bandwidth!) ;-)
> faster is good :)

escpecially half an order of magnitude! yummy!

> That would be cool.  :)  

Actually, its more likely to be warm ;-)

> > Well, My head is fscked now, and I still have to clean the kitchen,
> > before bed. night night...
> [snip of bootloader map]
> Interesting.  Makes me want to brush up on my assembly again. (and to
> think that my assembly class (the only time i've actually programmed
> in assembly) was only two years ago). 

Hehe ;-)

tell you what though - if you're feeling humbled by reading my assembly
stuff, try writing an emulator. (I did about a month back). Boy does
THAT teach you just hopw high level assembler is compared to machine

I never finished the emulator, but will probably revisit it sometime.
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