Memory mapping ( PC +DOS or WINDOWS )
Memory mapping ( PC +DOS or WINDOWS )
(OP)
When adding a new memory mapped peripheral what is the best
way to find an unused address ?
way to find an unused address ?
----------------------------
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RE: Memory mapping ( PC +DOS or WINDOWS )
RE: Memory mapping ( PC +DOS or WINDOWS )
On the PC as I know there is only one memory -- the main
one which adreeses one ROM ( for start-up, etc ) and one
RAM. The RAM may consist of any number of chips and may be
divided into pages using the uppper memory bits.
There is only one memory map and one I/O map.
Am I wrong ?
By the way I need the possible highest speed this is why
I have to use mem.map vs I/O map..
----------------------------
Please read FAQ240-1032
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RE: Memory mapping ( PC +DOS or WINDOWS )
Extended and expanded memory were bad enough. After that, things got seriously crazy.
You might consider putting your entire peripheral, including its memory and whatever processor it needs, into an external box, and connecting it to its user interface on the PC via USB or Ethernet.
Mike Halloran
Pembroke Pines, FL, USA
RE: Memory mapping ( PC +DOS or WINDOWS )
And how are you plugging in your memory-mapped device? Memory is accessed through PCI, PCI-Express, ISA, LPC, local buses, and others. It all depends on the type of PC. What are you trying to do?
RE: Memory mapping ( PC +DOS or WINDOWS )
TTFN
Eng-Tips Policies FAQ731-376
RE: Memory mapping ( PC +DOS or WINDOWS )
----------------------------
Please read FAQ240-1032
My WEB: <http://geocities.com/nbucska/>
RE: Memory mapping ( PC +DOS or WINDOWS )
What's the datarate?
TTFN
Eng-Tips Policies FAQ731-376
RE: Memory mapping ( PC +DOS or WINDOWS )
That's what _she_ said.
....... Oops, sorry, wrong discussion.
Mike Halloran
Pembroke Pines, FL, USA
RE: Memory mapping ( PC +DOS or WINDOWS )
_That's_ what she really said.
While you're trying to bracket your problem with numbers, including if you please how many such devices you plan to make, you might look up 'indeterminacy', as applied to Windows, and to DOS.
Mike Halloran
Pembroke Pines, FL, USA
RE: Memory mapping ( PC +DOS or WINDOWS )
In my application there would be very few bursts
longer than 2 to 4 bytes and the overhead shouln't
take more time -- assuming a CPU faster than 500 MHz.
operating preferably under DOS or linux.
If all these can be satisfied, there may be market for
several hundred to few thousand.
----------------------------
Please read FAQ240-1032
My WEB: <http://geocities.com/nbucska/>
RE: Memory mapping ( PC +DOS or WINDOWS )
Going back to your original question about finding an unused address, a properly designed PCI or PCI-Express card uses a moveable memory window and is assigned a base address by a combination of the BIOS and the OS. If you move the cards around or install other cards, the memory window assigned to any particular card may change. In Windows, you can see what the memory (or I/O) address range is by opening Device Manager and checking out the resources for your various hardware devices.
RE: Memory mapping ( PC +DOS or WINDOWS )
Sounds like a natural for a little hardware buffering, just to keep the overhead from bringing the machine down.
Mike Halloran
Pembroke Pines, FL, USA
RE: Memory mapping ( PC +DOS or WINDOWS )
Again, buffering will reduce the transaction overhead if you send bigger chunks of data.
TTFN
Eng-Tips Policies FAQ731-376
RE: Memory mapping ( PC +DOS or WINDOWS )
It is not continuous. The data frequency is variable but
the average may be very low. The 33 MHz would be fast enough.
Thank you all.
Could I learn more about the address selection under anything but WINDOWS?
By the way, I intend to use desktop, no more than a few years old.
----------------------------
Please read FAQ240-1032
My WEB: <http://geocities.com/nbucska/>
RE: Memory mapping ( PC +DOS or WINDOWS )
ht
Also:
http://www.pcisig.com/specifications/
TTFN
Eng-Tips Policies FAQ731-376
RE: Memory mapping ( PC +DOS or WINDOWS )
RE: Memory mapping ( PC +DOS or WINDOWS )
Here's a little bit of information on the PCI world from
the linux standpoint. Granted the OP was windows, however,
the hardware's the same:
http://tldp.org/LDP/tlk/dd/pci.html
Cheers,
Rich S.