Re: gEDA-user: series terminators

[DJ Delorie <dj@xxxxxxxxxxx>]

> 5 Volts?  How quaint.

Yeah, well, that's what the eval board uses.  My furnace controller
uses 5v too, because that's what the LCD panels need.  It throws in a
bunch of issues about level converting, though.

> You didn't give the thickness of the FR4 between the trace and the
> ground plane.

Double sided, 0.062.

> Series resistors for a bidirectional trace go near the middle of
> their length.  For unidirectional traces, place the resistor anywhere
> from the middle to the source end.

I figured that; they're going on the SRAM side of the DIN connector,
about in the middle of the run.

> It takes a good FET probe and a fast 'scope to characterize the
> system well enough to optimize on the bench.

I have a 32 Ms/s scope and a 500MHz logic analyzer, neither of which
is great for this kind of test, but might be close enough.

> Any resistor in the range of 25 to 150 Ohms will damp the ringing.
> Whenever I have this concern, I just put in 100 Ohms, observe that
> it works, and go on to the next chore.

Ok, sounds reasonable.

Thanks!


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