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authorFrancis Rowe <info@gluglug.org.uk>2015-04-11 02:51:44 (EDT)
committer Francis Rowe <info@gluglug.org.uk>2015-04-11 02:51:44 (EDT)
commit592610afc44807632c5720c0ab4446be2f2a20b4 (patch)
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docs/tasks.html: more notes about wp/hold
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</ul>
</li>
<li>
- Apparently, leaving HOLD# and WP# pins floating (unconnected) isn't a good idea.
+ Apparently, leaving HOLD and WP pins floating (unconnected) isn't a good idea.
Information online says that this needs to be connected along with 3.3V - look into this.
(it is specific to each flash chip, so read the datasheets).
+ <ul>
+ <li>
+ eg http://flashrom.org/FT2232SPI_Programmer -
+ &quot; The WP# and HOLD# pins should be tied to VCC! If you leave them unconnected you'll likely experience strange issues.&quot;
+ </li>
+ <li>
+ &lt;pehjota&gt; stefanct: We've never had any &quot;strange issues&quot; with leaving WP# and HOLD#
+ unconnected on the Macronix and Atmel SOIC-8 and SOIC-16 flash chips on the X200.
+ IIRC, the datasheets don't say how those pins are wired internally or whether they can
+ be left unconnected. But I tested their voltages while flashing, and they float high
+ on their own, so they seem to support it fine.
+ </li>
+ <li>
+ &lt;pehjota&gt; fchmmr: You would connect the WP# and HOLD# pins to 3.3 V (on an ATX PSU you'd
+ hook up more cables to the other orange pins, with your PSU I guess you'd wrap more wires
+ around the 3.3-V screw), just like you do VCC. But as I said above, it doesn't seem to
+ be necessary (WP# and HOLD# seem to be held high already).<br/>
+ &lt;pehjota&gt; I got a solid ~3.3 V (i.e. pulled high, not floating between high and low)
+ from WP# and HOLD# with just VCC, GND, MOSI, MISO, CS#, and SCLK connected. Plus, we haven't
+ had any write protection issues as I'd expect from floating WP# and HOLD#, AFAIK.<br/>
+ &lt;pehjota&gt; fchmmr: These pins do nothing if they're held high. The "#" (not) means they cause different behavior when held low.
+ </li>
+ <li>
+ &lt;stefanct&gt; fchmmr: pehjota: it may not be a problem if the chip is soldered to the x200, but it surely is when it isnt.
+ </li>
+ <li>
+ &lt;stefanct&gt; yes...
+ &lt;stefanct&gt; a small note noting that would be appreciated because there are enough people out there already that ignore those pins and get stuck
+ &gt;pehjota&gt; stefanct: You mean a note in the libreboot documentation explaining why we don't have to connect HOLD# and WP# to anything and how they would have to be tied to VCC on a chip not soldered to a board?
+ &lt;Kamilion&gt; How about a more useful note that explains the whole discussion you two had succinctly?
+ &lt;Kamilion&gt; Not everyone is going to be an EE to know about the # indicating the pin should be pulled low to be active.
+ &lt;Kamilion&gt; reminds me, I need to pull out my pomona and try to fix some intel NIC roms
+ &lt;stefanct&gt; pehjota: yes
+ </li>
+ </ul>
</li>
<li>
Adapt the notes at <a href="install/bbb_setup.html#stability">install/bbb_setup.html#stability</a>