[rescue] Sun serial cable pinout question (null modem)

[jodys at helluin.org]

On Thu, Aug 15, 2002 at 12:28:00PM +1200, Gavin Hubbard wrote:
> Hi Guys
> 
> I'm going to make up some null modem cables for my new Sun systems (using
> DB9/25-RJ45 shells).
> 
> The two pin-outs that I've seen for the Ultra 2 are:
> 
> 2-3
> 3-2
> 7-7

That will work, but only for software flow control, if making db-9 
connectors you will probably need
2-3
3-2
5-5
as db9 uses different pin wirings (pin 5 on db9 and pin 7 on
db25 are signal ground which you definitely need.

> 
> and
> 
> 2-3
> 3-2
> 7-20
> 20-7

This is slightly funny, it's connecting signal ground to dtr. Which,
I think, would mean that DTR is always low. Why you would want it
I don't know. For hardware flow control with DB25 you would want
something like, 

2-3
3-2
7-7
8-20
20-8  

which would connect DTR to DCD allowing hardware flow control, 
mostly (assuming you are not connecting to some ancient weirdly
wired serial device).

You might want to check out the Yost serial device wiring standard
http://yost.com/Computers/RJ45-serial/. It's certainly saved me 
a lot of headache.

Jody