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memory and absolute decleration ?

Posted on 2000-05-11
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Last Modified: 2010-04-04
Hi all

ok here go's Im currently accessing a ISA plug in card using memory read and write ... and it works fine ... no problems as long as the card address is in the c9000 range I can get direct comms by declearing a var absolute which works fine so there is no need to write a vxd ... what I want to know is

a: why ? lol

b: why only in that one address range ?
( any other range and the read write lines on the isa buss are not activated
)

and lastly ... there does not seem to be any system memory alocated to this adress ?

thanks stephen :)
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Question by:marchant
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6 Comments
 
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by:Madshi
ID: 2803563
Oh well, there are some secrets in win9x. E.g. memory mapped files are always mapped to the same address in each process and so on. Things like that are not documented anywhere, because they might change in a future Windows version.
So if your program relies on the fact, that IO calls work fine at $C9000, you might have bad luck already with Windows Millennium. My only recommendation can therefore be: Choose the safe way and write a vxd  :-(.
If you absolutely don't want to, if you choose to use the undocumented $C9000 way, test your program at least under all variants of win9x, that is win95 (old version), win95osr2, win98, win98SE, winMillennium.

Ehm, sorry, I can't answer your questions directly, hope my comment helps a bit, nevertheless...   :-)

Regards, Madshi.
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by:sistudio041900
ID: 2808642
I have written many VXD's - plain fun - and well, yes if you want be sure you get real direct hardware access on non-NT windows platform's you actually need to write a VXD. That isnt actually a big problem a generic VXD that does expose direct memory access has maybe 10 lines of unique assembly code :) well there are 42+ CD you have to dig first :) well if interested I will be publishing all source code written by me and/or copyrighted to Silicon Studio Inc. this will include maybe 12 VXD's and some Pascal programs that talk to those VXD's.
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by:Madshi
ID: 2808759
Hi sistudio, that sounds quite interesting! If you publish those sources, I would love to get a copy, too. I'm not doing any VXD development right now, but who knows what will be in 2 weeks. So having some good VXD examples would be a good starting point then...   :-)

Regards, Madshi.

madshi@gmx.net
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sistudio041900 earned 200 total points
ID: 2810122
i uploaded one project VXD source + sources of delphi units that talk to the VXD as:

http://case2000.isp.ee/files/PUMP1.ZIP

it pretty 'bad coding maybe' but at least you can see what needs to be done to implement a VXD and how to access the VXD functions from Delphi code

I have maybe over 10 more VXD's for which I could upload sources, but just too busy right now.
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by:Madshi
ID: 2810428
Thank you very much - that's kind!!   :-))
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by:marchant
ID: 2813228
thanks sistudio it seems I have to go with the flow and start wriing vxd's

any other pointers would be apriteated
ie any good boks out there ?
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