[Cryptech Tech] Alpha board BOM and PCB design requirements

[Fredrik Thulin]

On Monday, March 09, 2015 10:25:19 PM Павел Шатов wrote:
...
> 1. I can't understand what configuration mode you want to use: Master or
> Slave? Where will the bitstream be stored? 

(I don't know what you mean with Master and Slave here, because of my own FPGA 
ignorance I'm sure)

What we've talked about for the long term is to have the bitstream in the FPGA 
config memory.

dol@ always says it shouldn't be writable at all (in production) but I'm sure 
we all agree that it should at least require physical access to write it, such 
as installing a write-enable jumper (and the tamper boundary is broken so the 
MKM is naturally deleted at this stage).

For the Alpha board, we think it will be convenient to be able to download a 
FPGA bitstream into the FPGA from the ARM (funny, I would call it upload but 
JS says it's download ;)). To be able to sorta upgrade the protection of the 
Alpha board to the long term variant, we want this Alpha board feature to 
require a separate enable-jumper, that can then be removed if the Alpha board 
were to be used in something more than strict development.

Makes sense? 

> Btw, there's a typo, configuration can only be done using SPI, not I2C.

Thanks. Will update the wiki.

> > External RAM
> > 
> >     SO-DIMM DD3 modules. (Like the Novena.)
> 
> 2. Do you intentionally want to have SO-DIMM connector instead of
> discrete chips?

Not intentionally on my part. Joachim?

I guess if we go for discrete chips the need to decide on the exact amount 
(Randy's question) becomes even more important...

> 3. I believe your sketch is missing 4th section named "Power subsystem".
> How is Alpha Board going to be powered?

Good point. I've been thinking it would be an unwarranted complication to try 
and run the Alpha of USB, so I've been assuming an external wall plug for the 
Alpha. Opinions?

Related, when we talk battery do people think CR2032, 12V 6Ah Sealed Lead Acid 
battery or something else?

/Fredrik