GTA02 MPU alternatives

[Ian Stirling]

Werner Almesberger wrote:
> Ian Stirling wrote:
>> I have a project based on ST micros cortex chips that bit-bangs SDRAM, 
>> taking advantage of the block read function, and would in principle work 
>> for keeping the LCD state when the CPU is off.
> 
> That's nice ... but, could we perhaps start with a problem statement
> before the proposed solution ? I.e., what would this do that we want
> to do but can't or can only do with undesirable consequences ?

Sorry.
I was unfortunately rushed at the time, and probably shouldn't have 
posted without more thought.

The thought was that the chosen MPU might be able to fulfull multiple 
roles - amongst them being able to run the LCD of the GTA03/... when 
off, being able to  be used as an SD expander, providing the emergency 
recovery facility, ...

On reflection - this won't work so well as I understand it, as the RAM 
is inside the SoC - and adding external lines from the SDRAM to the MPU 
would cause probable congestion.
Also - I hadn't fully considered the number of lines - the design I was 
using was an 8M*8 SDRAM paired to a 8 bit display, which is considerably 
fewer (around 40) than the would be required by the 32M*32 (presumably) 
of GTA03, and voltages will likely not be a match.

I still think it's worth a look if a SD expander is also needed, though 
I have not actually used the SD/MMC functionality on these chips, or 
looked at it in depth yet.