[vdr] Re: Increasing SDRAM on DVB cards

[Stefaan Coddé <stefaan.codde@pandora.be>]

Oliver Endriss wrote:

>Joerg Schneide wrote:
>> Hermann Gausterer schrieb:
>> > look at page 13:
>> > there are other memory area`s the chip is accessing, not only that 
>> > single sdram .. and in that case, every access to the DP-RAM or the

>> > DRAM will result in read/write to your "second" chip so this 
>> > approuch cannout be used
>>
>> I don't have the datasheet,
>> but in general: If it is possible to decode out all other used areas 
>> with their CS-lines (or other signals that indicates reliable an 
>> access), then it is possible to use the concept.

>Hermann is right: This approach is not possible due to the memory usage

>of the AV7110. Simply look into the datasheet (p.13).

>The AV7110 is a very complex device with many built-in 
>functions/peripherals. Each of these reserves a part of the address 
>space. There are no external CS signals pins for the built-in 
>functions...

The AV7110 can control 4MB but only the half is used.
This half, 2MB is selected with the first chip select signal.
The second half with the second which is not accessible.

They will not use an adress range internal if it's ment original
for something else eg 4MB instead of 2MB and if that's the case
of the free area then you can use a non conventional chip select line
but that means a firmware change anyhow.

The question will be: where to fetch an chip select signal from?
          what about timing?

What about the select lines of the cam slot or combine two signals
a clumsy way would be applying a exclusive and function on all
address pins so you get a additional adress range which can be used 
as chip select signal for the second 2MB sdram.

Example :in this case 8 adress lines

A0 A1 A2 A3 A4 A5 A6 A7 A8
If they become all high and you perform exclusive and then you end up in
fact
with A9 which could be used as chip select for a second ram chip with 8
adress
lines in this case.

There you have your independent chip select signal.
The firmware must be modified then to think that there's a 4MB chip
mounted
cause it has to adress the entire 4MB range and not only the 2MB range.

That's the advantage of adressing, each address is 'unique'.

Does this makes sence for y'all?




  


 




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