Re: Sun widget

[Don NetBSD <netbsd-embedded%gmx.com@localhost>]

On 11/30/2018 4:34 AM, Julian Coleman wrote:
> Hi,
>
> > I have some little (3 inch) widgets with an RJ45 plug on one end and
> > jack on the other.  Carrying a (Sun?) part number of 422764100011.  I
> > suspect they may have been part of the Netra T5220 I recently acquired.
> >
> > First thought was perhaps a crossover adapter?  But, the Netra's inet
> > ports are Gbe so that shouldn't be necessary.  Unless it is intended for
> > use with the (100Mb?) "management port"?
> >
> > Or, perhaps a means of converting the serial management port's DB9<->RJ45
> > adapter to DCE/DTE pinout??
>
> The last.  If I remember correctly, this stems from Sun's interpretation of
> the serial standard, particularly which end was the computer and which end
> was the terminal.  Sun serial ports were wired as a computer, but PC's
> (maybe everyone copied the IBM PC?) were wired as a terminal.  When RJ45
> serial connectors replaced DB25/DB9 connectors, Sun continued to have the
> different wiring (also shared by Cisco) for its console connections.  So,
> if you connect a terminal server to a Sun or Cisco console, you'll need a
> crossover adapter.  The Avocent/Cyclades ADB0039 is the same, e.g.:
>
>    https://www.kvm-switches-online.com/adb0039.html

Another respondent (offlist) suggested similarly.

However, I finally sat down with an ohm-meter (my cable checker has
a faulty display... should get around to fixing that, one of these days!)
and a magnifying glass (eyes don't work as well as they used to) to
sort out the pin mapping.

It is *exactly* one-to-one.  I.e., it's just a 3 inch "extender cable".

Perhaps to make the tightly spaced network connectors on the rear of
the box more accessible to folks with fat fingers?  (That seems
ludicrous).

On closer inspection (now that I have the magnifying glass in hand), the
RJ45S end of the adapter is a *true* RJ45S and not just an 8P8C.  So,
while likely not something for which I'll have a frequent need, they're
still worth tossing in the box of "miscellaneous widgets" as *when*
needed, there won't be any practical alternatives (short of replacing
the cable)!