Well shoot... I got out my meter and tested continuity between all the
pin assignments. Come to find out I have one "null modem" cable that is
missing the 20/6<->8 assignment on both sides, and the other not-so-null
cable has some 4/5<->20 with 8<->8!!
I don't know whose idea these cables were if the chart below is the _real_
way, but I'll either have to warm up the soldering iron or see if my local
retailer has a _real_ one.
So to my next question, "Where's the standard?" Is the pin assignment
below the honest, documented null modem standard? Is it a Linux special?
What's with the other two I have that don't even agree with each other?
I don't remember my RS232 protocols from CSC404, but their can't
possibly be multiple ways of doing it... Is this another case of
manufacturers being lazy?
And another thing--that first cable--the one missing the 20/6<->8
connection--I used it to provide a console for a VME rack running
Solaris SPARC on a Force CPU card. It had no frame buffer, so we
plugged this cable in between the first serial port and a 486-Linux
box. It worked, so why not now?
Brendan
> If you build your own cable anyway it's best if pin 20 is tied to the remote
> pin 6 as well as 8 rather than pulling 6 high locally.
> jepp
>
> >
> > Pin Name Pin Pin
> > Tx Data 2 ----------------------------- 3
> > Rx Data 3 ----------------------------- 2
> > RTS 4 ----------------------------- 5
> > CTS 5 ----------------------------- 4
> > Ground 7 ----------------------------- 7
> > DTR 20 -\--------------------------- 8
> > DSR 6 -/
> > RLSD/DCD 8 ---------------------------/- 20
> > \- 6
> >
> > And here is my rather cryptic 9 pin to 25 pin map:
> >
> >
> > 5 4 3 2 1 f 1 2 3 4 5 6 7 8 9 10 11 12 13 m
> > 9 8 7 6 14 15 16 17 18 19 20 21 22 23 24 25
> >
> > 1 rlsd=cd 8 2 rd 3 3 xd 2 4 dtr 20 5 gnd 7 6 dsr 6 7 rts 4 8 cts 5
> > 9 ring 22 xcl 9 -xcl 11 rcl 18 -rcl 25
> >
> > You might find the Serial-HOWTO helpful, too.
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