On May 14, 9:20*pm, Mike Harrison <m...@whitewing.co.uk> wrote:
> What I'm looking at is the cheapest way to drive a large number (potentially hundreds) of
> distributed TFT (PSP) displays with local SDRAM and/or NAND flash storagefor a few tens to hundreds
> of frames, with a relatively a low bandwidth network of some sort to update content in non-realtime,
> and switch the display between stored frames realtime. The aim is to minimise the cost per node as
> much as possible.

Ah, so you need many slaves, and the smarts can be elsewhere.

I found some info on TFT(PSP), [9MHz, 8+8+8 Colour] and it seems the
simplest solution would be a 32 bit wide SDRAM
and a CPLD, and 128MC should be plenty.
- I don't see you need a line-ram in a SDRAM playback scheme (tho the
Qimonda SDRAM data I had was poor ).

Run the CPLD at >> 9MHz (or whatever is needed to interleave access),
and a simple BUS connect CPLD.SDRAM.TFT,
then something like nibble-wide SPI to link all the slaves.

We have done simple cascade shifters, when doing similar designs - all
slaves chain, and here ~13 clocks are needed per slave node.
>
> Interesting - I'd not noticed that one - I've used Atmel CPLDs in the distant past but had sort of
> forgotten that they still did them as they don't seem promote them very much these days..!

They are poor on promotion, which is a shame as they have nice parts.

-jg