docs/85355: [patch] Error in the pin numbers of the described connector in the Handbook (serial).

[Gary W. Swearingen]

The following reply was made to PR docs/85355; it has been noted by GNATS.

From: garys at opusnet.com (Gary W. Swearingen)
To: Julien Gabel <jpeg at thilelli.net>
Cc: bug-followup at FreeBSD.org
Subject: Re: docs/85355: [patch] Error in the pin numbers of the described
 connector in the Handbook (serial).
Date: Sat, 27 Aug 2005 13:40:19 -0700

 Julien Gabel <jpeg at thilelli.net> writes:
 
 > +	  <para>If you like making your own cables, you can construct a
 > +	    null-modem cable for use with terminals.  This table shows the RS-232C
 
 "for asyncronous communications with terminals".  (I'm not sure what
 "terminals" include, but synchronous comm needs more wires.)
 
 (I'd also kill "If you like making your own cables, ".)
 
 > +	    signal names and the pin numbers on a DB-25 connector.  More information
 > +	    and collection of cable descriptions may be found in the <ulink
 > +	    url="http://www.hardwarebook.net/cable/index.html">Hardware Book</ulink>.</para>
 
 I'd add: The standard also calls for a straight-through pin 1 to pin 1
 "protective ground" line, but it is often omitted.  Some terminals can
 get by using only pins 2, 3, and 7, while others, especially printers,
 require other configurations than the example here.  Synchronous
 communications, for example, requires more lines to be used.
 
 > +		  <entry>8</entry>
 > +		  <entry>DCD</entry>
 
 That design (after the fix) seems to be the most popular, but a book
 "RS-232 Made Easy" uses several pages developing and justifying a
 generic null-modem design like that, except he has 4 & 5 going to 8
 and vice versa.  I probably used in at least one of my cables.  Oh,
 well; that's life with RS-232.