[LinuxBIOS] SPI flash focus
segher at kernel.crashing.org
Sat Nov 25 02:49:32 CET 2006
> If grounding HOLD# at power-on is working for people so far, that's
> great to hear.
You don't even *need* a BIOS-saviour like solution like
this; SPI flash chips are quite easy to program in-system
(if the system is designed correctly), either with the
board powered on or off.
> The SST datasheet implies that this is not the specified behavior, in
> fact my reading is that HOLD# is only sampled on SCK, and with CE# low.
HOLD# makes the flash chip not drive SO, and it would only do that on
SCK with CE# selected anyway. What am I missing?
> If the chipset drives HOLD# directly, though, it gets a little messier;
> then it may be best to put a tristate-able buffer on the SO8-clip and
> overdrive the mobo's SPI flash signals for the 1-2 seconds needed to
> rewrite the whole thing,
It's more like 10 seconds per megabyte, with a fast SPI interface.
> tristating as soon as the write is finished.
> That starts to require a pretty fast interface, driven over a cable,
> now it's a lot messier than simply hotswapping a PLCC chip!
In-circuit programming is a lot easier, heh. Many boards have a
header for this btw, no clip needed. The manufacturers have
similar problems during manufacturing you know :-)
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