[Arm-netbook] [EOMA68-A20] SATA testing

luke.leighton luke.leighton at gmail.com
Wed Sep 4 23:15:32 BST 2013


On Wed, Sep 4, 2013 at 8:14 PM, joem <joem at martindale-electric.co.uk> wrote:
>
> um... anyone got any ideas as to why the voltage levels on Tx+ and Tx-
> are 0.5V?  is that normal?
>
> --
> Yes its a differential interface that works on current instead of using voltage signaling.

 yyyyeeuuurgh.  ok.

> If you want to see the signals, you could cut the track, put a serial 0.1R resistor
> attach the scope probes across the resistor, and turn up the scope sensitivity.
> You might see the packets flying past but probably not the signal itself as that
> is running into GHz range. Higher values of resistor may work, but it all depends...

 ok.  current signalling.  via capacitors.  wow.  so what the heck is going on?

 hmmm... let me check the track lengths, make sure they're precisely balanced...



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