Hello!

I have an application where I need to connect a few serial
terminals to a NetBSD host.  They'll be closer than 15m, so
I shouldn't need any fancy RS-422 adaptors or anything.

My normal DTE-DTE 'null-modem' cable crosses over the data
lines, RTS and CTS, and uses DTR at one end to drive both
DSR and DCD at the other.  If there's at least one DB25
connector, I connect the cable's screen to the frame ground
at one end only.  It's a configuration that has worked well
for me over the years.

Being the cheapskate that I am, I was wondering whether
NetBSD normally uses the DTR, DSR or DCD pins to convey
useful information between a host and a terminal.  If not,
I was thinking that I could use 5 core cable instead of my
usuall 7 core.  I'd loop back DTR to the DSR and DCD inputs
at each end.

Off-the-shelf cables may work out cheaper, but that aside,
is there any compelling reason why I shouldn't use the
alternative wiring I've described?

   My normal DTE - DTE cable       Possible Alternative?

   9D                    25D
   3 TXD -----\/----- TXD  2       TXD -----\/----- TXD
   2 RXD <----/\----> RXD  3       RXD <----/\----> RXD

   7 RTS -----\/----- RTS  4       RTS -----\/----- RTS
   8 CTS <----/\----> CTS  5       CTS <----/\----> CTS

   4 DTR -----\/----- DTR  20      DTR --,      ,-- DTR
   6 DSR <-+--/\--+-> DSR  6       DSR <-+      +-> DSR
   1 DCD <-'      `-> DCD  8       DCD <-'      `-> DCD

   5 SG  ------------ SG   7       SG  ------------ SG

The host in question is a PC, and the PC serial port may
have some quirks <blatantly tenuous attempt to justify
posting to port-i386 ;->

Regards,
  - Andy Ball