Re: [flashrom] SOIC8 test clip - cant write to BIOS SPI flash chip - flashrom

Oct. 17, 2015

      Dear Nico,
...
It might be easier to help if we knew your Laptop model. Also, please
provide a full log of the failing flashrom run with the -V switch, you
can specify a log file with -o.
Right now I'm away from that laptop and cant remember its model
(or provide a flashrom log) However I remember the most important thing:
the model of BIOS SPI flash chip is EON EN25QH32 which is supported by 
flashrom since version 0.9.6 . I got a latest datasheet at official EON
website
( here it is - http://www.eonssi.com/upfile/p2013114174725.pdf )
...
Please further define "without problems". Did you try several reads
and
...
compared the contents?
Yes I tried several reads and the contents of flash chip are always the
same.
Moreover, I was able to successfully write 00s and FFs for a few times,
and
right now the contents of SPI flash chip: 00's - first 1MB , FF's - last
3MB
...
By guessing two possible issues come in mind: 1. Your programmer
doesn't provide
...
enough power for erasure. 2. The write protection pin of your flash
chip is asserted.
Because I was able to write at least some stuff, I believe that your 1st
theory is true:
maybe a part of current that should be going to flash chip for a
successfull write,
is powering a half of the surrounding circuit instead...
...
I'd try with the AC adapter. In that case Vcc must _not_ be connected
to
...
your programmer. GND, OTOH, has to stay connected.
Not forbidden. It's sometimes even encouraged because there are boards
where the Vcc pin of the flash chip is directly connected to other
chips, which would draw down the power from the programmer.
Thank you very much for advice, Nico! As soon as I get back to equipment
I am
going to disconnect a Vcc pin from a programmer to avoid the overvoltage
(just checked the datasheet above and Vcc is the 8th leg of that flash
chip)
Hopefully it will be powered good enough by the AC adapter ;-)

Just not sure what to do with a CMOS battery, too afraid to connect it
back
together with AC adapter - if there would be overvoltage I am screwed...
...
...
Or its better to try to power Vcc of flash chip from "USB to TTL"
adapter - which has this 3V3 (3.3V) voltage pin?
It really depends on your machine.
EN25QH32 datasheet tells that this flash chip supports between 2.7V and
3.6V,
3.3V seems OK and I would probably try taking it to Vcc from "USB to TTL
adapter"
if the solution with a laptop's AC adapter will not work...

AC adapter would also powering EC controller, so what if EC will setup a
write protect?

Best wishes,
Robert Brown

<-----Original Message----->
...
From: Nico Huber [nico.h at gmx.de]
Subject: Re: [flashrom] SOIC8 test clip - cant write to BIOS SPI flash
chip

...
On 17.10.2015 02:07, Robert Brown wrote:
...
But here is a problem: I could read a dump from this BIOS chip
without
...
...
problems, however
...
it fails when I am trying to write - so the contents of BIOS flash
chip
are remaining unchanged.
Log please. By guessing two possible issues come in mind: 1. Your pro-
grammer doesn't provide enough power for erasure. 2. The write protec-
tion pin of your flash chip is asserted.
...
Should I connect to motherboard a laptop's power battery, or small
CMOS
battery, or AC adapter of laptop,
I'd try with the AC adapter. In that case Vcc must _not_ be connected
to
your programmer. GND, OTOH, has to stay connected.
...
so that this Vcc pin would be powered by them, or it is forbidden to
do
it while using SPI programmer in the same time?
Not forbidden. It's sometimes even encouraged because there are boards
where the Vcc pin of the flash chip is directly connected to other
chips, which would draw down the power from the programmer.
...
Or its better to try to power Vcc of flash chip from "USB to TTL"
adapter - which has this 3V3 (3.3V) voltage pin?
It really depends on your machine.
Nico
.
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Re: [flashrom] SOIC8 test clip - cant write to BIOS SPI flash chip

Robert Brown

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