RE: [Gumstix-users] jtag questions

[Gordon K. <go...@gu...>]

So, here is the schematic.  As always:
1) it is unwarranted and may contain errors I don't know about,
2) as well as errors that I do know about but have forgotten to mention.

The error I DO recall is in the power section:  I use the MIC5207 for =
power, which in fact should be
used with a tantalum cap, but is not.  I also did not use a byp/adj cap =
that is suggested to handle
noise.

There is a huge variety of jtag circuits and of usage of tie-high/low =
resistors.  I believe this
version of the gumstix-wiggler interconnection is what I still use =
day-to-day.

Gordon


> -----Original Message-----
> From: gum...@li...
> [mailto:gum...@li...] On Behalf=20
> Of Zach Welch
> Sent: Tuesday, March 23, 2004 3:42 PM
> To: gum...@li...
> Subject: Re: [Gumstix-users] jtag questions
>=20
>=20
> Zach Welch wrote:
> > I'll keep playing with it, but Gordon might be able to shed
> some light
> > on this (i.e. are there any hidden gotchas that i'm missing?).
>=20
> Well, after having said that, I went and looked in the Design
> Guide again.  This time, I looked at the default JTAG header=20
> for the Lubbock design (whose schematics are in the back). =20
> It shows a couple of significant additions to the board,=20
> which (not having the schematics) I can not determine are=20
> on-board or need to be added to my offboard header.
>=20
> Specifically, page 11 of the diagram shows there is a pair of
> resistors (10K and 100K) giving bias to the /TRST signal=20
> (effectively pulling it high).  There is also a 75 ohm=20
> resistor in series with TDO.
>=20
> I am presently assuming these parts need to be added to the
> header, but it would be nice to hear confirmation of this=20
> stab in the dark.
>=20
> Cheers,
>=20
> Zach
>=20