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<p class="MsoNormal"><span style="color:#1F497D">Leigh,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo3"><![if !supportLists]><span style="color:#1F497D"><span style="mso-list:Ignore">1)<span style="font:7.0pt "Times New Roman"">
</span></span></span><![endif]><span style="color:#1F497D">Yes this is an acceptable approach. It’s not the cleanest solution, but it should work as long as your power up sequence is followed.<o:p></o:p></span></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo3"><![if !supportLists]><span style="color:#1F497D"><span style="mso-list:Ignore">2)<span style="font:7.0pt "Times New Roman"">
</span></span></span><![endif]><span style="color:#1F497D"> Just remember the i2c interface on the HSE is at 1.8V , so if you are connecting it up to the mPCIe connector you will need to level shift it to 3.3V. make sure you include the appropriate caps in
series for the PCIE_TX pair coming from the HSE. <o:p></o:p></span></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l0 level1 lfo3"><![if !supportLists]><span style="color:#1F497D"><span style="mso-list:Ignore">3)<span style="font:7.0pt "Times New Roman"">
</span></span></span><![endif]><span style="color:#1F497D">The two implementations we have tested use the PWROK or a basic RC for the PERST# signal on the mPCIe connector. In fact all of the designs we have tested have zero ohm resistor options so either may
be used. I would not recommend using the #PMC_PLTRST_R_V1P8 signal.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Feel free to post schematics for review! Good luck with the design!<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Thanks<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D">Dave Anders<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b>From:</b> elinux-MinnowBoard [mailto:elinux-minnowboard-bounces@lists.elinux.org]
<b>On Behalf Of </b>Leigh Gawne<br>
<b>Sent:</b> Monday, March 9, 2015 5:10 AM<br>
<b>To:</b> elinux-minnowboard@lists.elinux.org<br>
<b>Subject:</b> [MinnowBoard] System power/reset control architecture with PCIe<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span lang="EN-GB">Hi all,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">I am in the process of designing a custom expansion board for the MinnowboardMax (really liking my experience with this board so far BTW :-) and have a question regarding PCIe power supplies.
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">One of the interfaces I am implementing on the expansion board is a Mini PCIe card slot. On my expansion board, I have all the required power suppliers for card slot, and hence don’t need to rely on any power coming from
the MinnowboardMax expansion connector.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">There is a requirement in the Atom e38xx documentation (actually a PCI Express 2.0 spec requirement) that all power rails associated with PCIe should be valid for ~100ms prior to PMC_CORE_PWROK assertion.
<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">From what I can see in the MinnowboardMax schematic, there is an RC which controls the assertion of SYS_PWRGD providing 100ms delay as part of the power sequencing. My understanding is that as long as I ensure that my
PCIe supplies are up before providing 5V to the MinnowboardMax, then I should be meeting this requirement. So a couple of questions just for clarification:<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l1 level1 lfo2"><![if !supportLists]><span lang="EN-GB"><span style="mso-list:Ignore">1)<span style="font:7.0pt "Times New Roman"">
</span></span></span><![endif]><span lang="EN-GB">Is this an acceptable approach to take given the MinnowboardMax power supply architecture? I have a seen there is a Lure expansion board that includes mini PCIe and I presume this derives the required supplies
from those provided on the expansion header (perhaps the +5VSB supply, which should also mean this constraint is met).<o:p></o:p></span></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l1 level1 lfo2"><![if !supportLists]><span lang="EN-GB"><span style="mso-list:Ignore">2)<span style="font:7.0pt "Times New Roman"">
</span></span></span><![endif]><span lang="EN-GB">Any other recommended design approach? Backfeeding is always one area of concern I have which I need to manage carefully – just want to make sure there is nothing else I am overlooking/am not aware of.<o:p></o:p></span></p>
<p class="MsoListParagraph" style="text-indent:-.25in;mso-list:l1 level1 lfo2"><![if !supportLists]><span lang="EN-GB"><span style="mso-list:Ignore">3)<span style="font:7.0pt "Times New Roman"">
</span></span></span><![endif]><span lang="EN-GB">I am intending on using #PMC_PLTRST_R_V1P8 as the system reset signal for PCIe card slot and some other devices (with appropriate buffers) – any thoughts here?<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Many thanks for any information/clarification!<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Regards,<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB">Leigh<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-GB"><o:p> </o:p></span></p>
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