[vdr] Re: Increasing SDRAM on DVB cards

[Oliver Endriss <o.endriss@gmx.de>]

Hermann Gausterer wrote:
> after some mandatory sport i am back again ;-)
>
> in the meantime, i have studied the pdf of the av711x
>
> some NEWS ;-)
>
> > > SCS1 ? 0xCC00 0000 - 0xCC1F FFFF
> > > SCS2 ? 0xCC20 0000 - 0xCDFF FFFF
> > > so each has a range of 2Mbyte
>
> if you look closer, you can see that the second space is
> much greater the the first, the first is equal to 2Mbyte
> but the second is equal to 32Mbyte

I guess this is a typo, should read 0xCC20 0000 - 0xCC3FF FFFF

> but the docu speaks only from 16mbit rams .. so this is
> inconsistent .. but that does not disturb me at the moment
>
> next on page 20, we see the memory layout of an PAL chip
> (looks quite simular to my guesed one ;-)

This is the memory layout of the ARM in PAL mode.
As Ralph wrote on the other list some time ago, the memory layout in the 
the datasheet doesn't match the real one.

> and from this layout we can extract real new INFO :-))

At least you can tell that the second chip selects decodes a 2MB range, 
not a 32MB range.

> we see that the lower array is used for audio and video
> the higher for osd ...
> but whats new here .. new is that the second array
> the OSD .. is selected with the, in the meantime "famous"
> SCS2 line ;-) (page 19 says this)

Agreed.

> so ... what can we do here? we can only extend the OSD
> memory and nothing more . and that to a maximum of
> 32 Mbyte .. and i think that is enough for a true color OSD ;-)

OSD is limited to 720x576 @ 256 colors (page 41/42).

> so again, we can nothing more and nothing less do then search
> for an pin-compatible 64 mbit chip and solder it to the board

I am convinced that you can do *everything* with the RAM which can be 
done in SDRAM space. I guess you have to define some kind of memory 
layout and pass it to the RTL...

> we cannot do anything like an external adressdecoder we all
> learned at school, because the ram is adressed with a
> timemultiplexed adressbus (row & column)

??? For a decoder you never use the address lines which are fed into the 
RAM. You need the *upper* address lines!

According to the memory map the ARM has an address range 
from 0000 0000 .. FFFF FFFF. This corresponds to 32 address lines.
The RAM gets A0..A11 multiplexed, so you can address the lower 22 
address bits, not more. Obviously, SCS1/SCS2 are constructed using the 
upper address lines and address 2MB address space each.

> there are ENOUGH adresslines solderd to the chip

No, see above.

> the real problem is to find another chip .. ore the hard way
> make an riserboard with an complitly different dram chip
> and solder it with wires to the right pins
>
> > Well, thanks for pointing out this page - I guess I must have been
> > blind so far, not to have seen this...
>
> it is now the first time i was looking to this docu ;-)
>
> > So basically this means that we definitely need access to SCS2,
> > otherwise we can flat out forget about this.
>
> again:
> the scs2 is allready routed to the osd ram chip ... i hope the

Don't think so.

> HY57V161610D is the one used for OSD and not the other
> but i read today somewhere which chip is used for what

If SDRAM is in the range CC00 0000+, it uses SCS1.
(If it's in the range CC20 0000+, is uses SCS2).
A firmware developers can tell us...

Oliver


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