PXA25x Boot flash same as mass storage flash?

Do you have a question? Post it now! No Registration Necessary

Translate This Thread From English to

Threaded View
Hi.

I am about to start a design based on PXA255 and for economy I was
thinking of using the very same flash (or flash pair) for both boot
loader and general storage (kernel and file system), maybe using flash
internal mechanisms (and perhaps some glue logic) for protecting boot
blocks from accidental erasing. I have seen at least two PXA255 based
boards that have a flash for RedBoot only and place kernel and file
system in other flashes. Is there any mistake with my design? If not,
why not using the same flash for boot loader and normal storage?

Thank you very much for your advice.

Elder.

Re: PXA25x Boot flash same as mass storage flash?
Quoted text here. Click to load it

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

Re: PXA25x Boot flash same as mass storage flash?
Quoted text here. Click to load it

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.

Quoted text here. Click to load it

I need 8MB or 16MB at most.

Thanks for the hints.

Elder.

Re: PXA25x Boot flash same as mass storage flash?
Quoted text here. Click to load it

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.

Re: PXA25x Boot flash same as mass storage flash?
snipped-for-privacy@larwe.com (Lewin A.R.W. Edwards) wrote in message
Quoted text here. Click to load it

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.

Re: PXA25x Boot flash same as mass storage flash?
Quoted text here. Click to load it

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).



Site Timeline