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From: panek@hp-and.HP.COM (Jon Panek)
Newsgroups: comp.sys.hp
Subject: Re: How to test serial port?
Message-ID: <13060008@hp-and.HP.COM>
Date: 29 Nov 90 14:38:56 GMT
References: <1990Nov28.111522@dali.gatech.edu>
Organization: HP Andover Division (Massachusetts)
Lines: 64

|	Some hardware guru help me please!!!!  Is there a hardware HP
| number I can call and yell (calmly) into?  
|
|	Does anybody know what each of the 9 pins in a HP 9000 370
| do?  So far I've guessed:
|	pin	function
|	---	------
|	1	chassis ground
|	2	transmit data
|	3	receive data
|	5	clear to send
|	6	data set ready
|	7	signal ground
|
|	Are these right?

The complete pin-out for a 9-pin RS-232 connector (DCE) is as follows:

        pin     function
        ---     ---------------
         1      CD  Carrier Detect
         2      RX  Receive Data
         3      TX  Transmit Data
         4      DTR Data Terminal Ready
         5      GND Chassis Ground
         6      DSR Data Set Ready
         7      RTS Request To Send
         8      CTS Clear To Send
         9      RI  Ring Indicator

And so to get this to work, you need to connect 

        DCE         DTE
        ---         ---
         TX          RX
         RX          TX
        GND         GND
        DTR         DTR
        DSR         DSR
        RTS         RTS
        CTS         CTS

You can safely ignore RI and CD, usually.

The lowest-level "handshake" are the RTS/CTS and DTR/DSR signals.  The
DTR/DSR are supposed to be used for "On-Line" or "Connected" type info-
rmation, and has been used as a level 1 handshake.

Depending on how the software is written, the RTS/CTS lines may or may
not make a difference.  Some port drivers require these lines to be set
correctly before they'll squirt information out the port.

I would recommend you buy the correct, full-fledged cable for your application
and see what happens.  I have spent, literally, days of accumulated time
hacking up RS-232 cables of various flavors and vintages, and still find
that I can spend additional hours on each one connecting, cross-connecting,
looping back, or grounding any or all of the various hardware handshake lines.

Good Luck.

Jonathan Panek
Hewlett-Packard, Andover Division
panek@hp-and.an.hp.com
(508) 687-1501