[flashrom] 3COM NIC modification for >128kB flash.
krasnaya.zvezda at gmail.com
Sun Aug 23 11:22:38 CEST 2009
I was playing with modifying the supported 3COM NICs to support larger
than 128kB chips.
It's been a success so far, and seems to be functioning well with 256kB
chips. I haven't tried with 4Mbit/512kB yet, and I don't remember the
last time I've seen an 8Mbit [DIP] one. I need to add 28pin DIP and
32pin PLCC sockets yet - that should cover the whole 28F/29F family.
It will need some work for the 512kB chips to work. On <512kB chips, pin
1 is either Vpp or /RST, so it has to be high. On the 512k chips, it's
A18, so it has to change. For now, I have a pullup on it, and a switch
to the bankswitching latch(A18). So when the switch is open, there is no
support for 512k chips, but smaller should be fine... I should be able
to take care of this in software though. I guess just have it turn the
line on at init, and drop it if the probe determines a 512k+ chip.
There's only a few bits of the latch used, so the others can be used for
general purpose outputs. Right now I have two of the bits tied to LEDs,
and the code set to turn on one or the other, depending whether it is in
a write or read routine.
With some hardware work, off the other outputs - I should be able to
switch higher voltages to Vpp for the 27xxxx EPROM, I hope, but that's
for another day.
Here's a photo of the current card. Not very pretty, but once I get the
kinks out, I should be able to get some (much smaller) add-on PCBs made,
that will just plug into the stock plug on the NIC.
Schematic, as is:
Schematic (minimalistic version):
I think for the demo board, Maybe I'll add another decoder and an 8255..
then I'll have 3 bytes of GPIO - for whatever.
Schematics, pictures, etc, related to this are CC-SA if you want them
Anyways, any ideas, comments, criticism, etc, would be welcome :-)
Oh yeah - one thing I've noticed, after read, write, or erase, the
shutdown routine is called, but it *isn't* called after a probe. (on
3com NICs at least). Is that correct behaviour..?
I noticed this, because the latch leaves LEDs on after a probe, but not
after R/E/W (the shutdown function clears the bankswitching latch).
More information about the flashrom