PXA25x Boot flash same as mass storage flash?

The very high density flashes you want for filesystems do not support the random access needed for direct execution of firmware. I just did a PXA255 design and included two chips for boot flash (8M x 32 bits total) and two chips for filesystem flash (256M x 8 bits total).

If you can get enough random-access flash into your system to meet your needs, then that's the only kind you need to have.

-- Dave Tweed

Hmmm... I was thinking of Intel strata flash (28F320J3 or K3 - or their higher density siblings) and compatibles. A quick glance through the data sheet gave me the impression they can stand random access. I have to take a deeper look at it though.

I need 8MB or 16MB at most.

Thanks for the hints.

Elder.

I've done this, though not on ARM-cored products. It worked out to be more expensive than using a tiny (16Kbyte) boot flash loading the main OS out of NAND flash, though. NAND flash is dirt cheap, and pin-compatible for sizes from 8Mb to 128Mb.

RedBoot requires 128KB at least. I am considering putting it into the same flash more for space saving than for cost though it also matters a lot. We've been asked to use TSOP instead of uBGA so only PXA255 will be BGA and space may become an issue in this design.

Regards.

Elder.

Well, board space is board space... but what I wound up doing was using an OTP EPROM. *Everything* software-wise is on the NAND. The OTP only contains enough code to boot the OS out of NAND flash. The NAND is partitioned into "OS" and "data" areas using a wholly DOS-esque partition table. If I was using RedBoot, I would have had it on the NAND, compiled for RAM start-up (I'm assuming the terminology hasn't changed since I last used it).