Message-ID: <2362@nsc.UUCP>
Date: Thu, 14-Feb-85 15:06:26 EST
Article-I.D.: nsc.2362
Posted: Thu Feb 14 15:06:26 1985
Date-Received: Fri, 15-Feb-85 05:22:59 EST
Distribution: net
Organization: The Village
Lines: 13

Sigh. I've asked this before, and succeeded in misplacing the answers. Can
someone drop me a note with the pinouts I need to get a Macintosh to tie
into an RS232 line? 

Thanx,
	chuq

-- 
From left field, near the warning track:          Chuq Von Rospach
{cbosgd,fortune,hplabs,ihnp4,seismo}!nsc!chuqui   nsc!chuqui@decwrl.ARPA

Even though a poem be a thousand words, but made up of senseless words, one word
of a poem is better, which if a man hears, he becomes quiet. --The Dhammapada

Message-ID: <1841@tekig1.UUCP>
Date: Mon, 18-Feb-85 14:19:23 EST
Article-I.D.: tekig1.1841
Posted: Mon Feb 18 14:19:23 1985
Date-Received: Fri, 22-Feb-85 01:03:25 EST
References: <2362@nsc.UUCP>
Distribution: net
Organization: Tektronix, Beaverton OR
Lines: 25

From postnews Mon Feb 18 11:17:37 1985
 >  Sigh. I've asked this before, and succeeded in misplacing the answers. Can
 >  someone drop me a note with the pinouts I need to get a Macintosh to tie
 >  into an RS232 line? 

*** REPLACE THIS LINE WITH YOUR MESSAGE ***
*** NO! ***

The following four connections will make your Mac RS-422 connector into a
standard RS-232 connector.  Building a cable with a female 9-pin D connector on
one end and a female (or male, depends upon your modem) 25-pin D connector on
the other is the easiest way to do this.

	RS-422			RS-232
	(Mac 9-pin)		(Modem 25-pin)

	3			7
	5			2
	7			20
	9			3

Good telecommuning!

-Scott Phillips
Tektronix, Inc.

Message-ID: <16500011@ur-univax.UUCP>
Date: Tue, 5-Mar-85 16:13:00 EST
Article-I.D.: ur-univa.16500011
Posted: Tue Mar  5 16:13:00 1985
Date-Received: Sat, 9-Mar-85 11:40:51 EST
References: <2362@nsc.UUCP>
Organization: University of Rochester: Computing Center
Lines: 55
Nf-ID: #R:nsc:-236200:ur-univax:16500011:000:2159
Nf-From: ur-univax!ning    Mar  5 16:13:00 1985


 >  The following four connections will make your Mac RS-422 connector into a
 >  standard RS-232 connector.  Building a cable with a female 9-pin D connector
 >  on one end and a female (or male, depends upon your modem) 25-pin D connector
 >  on the other is the easiest way to do this.

 >  	RS-422			RS-232
 >  	(Mac 9-pin)		(Modem 25-pin)

 >  	3			7
 >  	5			2
 >  	7			20
 >  	9			3

I have just finish building an RS-232 cable for my Mac/modem, and it works
beautifully.  But I didn't use the diagram above, and unfortunately, the
diagram above doesn't work with software that looks for the RS-232 signal
called DCD (Carrier Detect).

The problem is the way it uses the pin 7-to-20 connection.  Pin #7 on the Mac
is a "listen" line called HSC (High-Speed Carrier?) in RS-422 lingo.  Pin #20
on a DB-25 is a "talk" line called DTR (Data Terminal Ready) in RS-232 lingo. 
The problem is that a modem doesn't send a DTR signal.  (It sends a
DSR (Data Set Ready) on pin #6, but this is irrelevant, because the Mac is
looking for a "Carrier Detect.")  The right connection for a DCD is pin #8 on
a DB-25.

Now that the two "carrier detects" are hooked up, this is what happens.
The Mac tells the modem to dial, and when the modem gets the carrier from a
remote modem, it makes true the DCD line.  When the Mac "hears" a true from
its HSC line, then it knows that a distant modem has been hooked-up.  Of
course, software that ignores the DCD will work, but it might get you sometime
in the future.

I used the diagram found in the "Open Window" section in March's issue of
MacWorld.  The article there shows how to hook a Mac up with a Volksmodem. 
So, I simply matched the signal *names* from the Volksmodem with a D-25
connector.  This was my end result:

	Macintosh	Modem		RS-232 Signal Name
	(9-pin DTE)	(25-pin DCE)

Pin #	3	<--->	7		Signal Ground (GND)
	5	---->	2		Transmit Data (TxD)
	9	<----	3		Receive Data (RxD)
	7	<----	8		Data Carrier Detect (DCD)

Note that a cable built this way will also work for a simple RS-232 line to a
mainframe.


John Lam______________________________________
{allegra,seismo,inhp4}!rochester!ur-univax!jnl

PS. No flame intended. (:-)

Message-ID: <154@unccvax.UUCP>
Date: Fri, 8-Mar-85 08:57:12 EST
Article-I.D.: unccvax.154
Posted: Fri Mar  8 08:57:12 1985
Date-Received: Mon, 11-Mar-85 07:08:09 EST
References: <2362@nsc.UUCP>, <16500011@ur-univax.UUCP>
Organization: UNC-Charlotte
Lines: 17

Most of the mac<->modem pinouts I have seen on the net have neglected DTR.
Some modems require a high signal on pin 20 (DTR) in order to connect,
answer the phone, or do anything but sit there.  On some this is an
option which can be switched off.  In any case you must either turn the
option off or strap DTR high.  Most modems supply a constant high on pin
9 and jumpering it to pin 20 should do the trick.  Pin 6 (DSR) may also
be an alternate source for this signal.

*  Strapping DTR high also implies that the modem always thinks the mac
is ready and waiting to communicate so it may answer your phone when you
least expect it.  This can be very annoying to sweethearts, customers, 
and bosses, since the modem usually answers on the first ring and you
don't. So turn the modem off when not actually in use or awaiting calls.

happy telecommunicating

jsp

Article-I.D.: ur-univa.16500012
Posted: Sun Mar 17 11:12:00 1985
Date-Received: Wed, 20-Mar-85 03:25:38 EST
References: <2362@nsc.UUCP>
Organization: University of Rochester: Computing Center
Lines: 65
Nf-ID: #R:nsc:-236200:ur-univax:16500012:000:2973
Nf-From: ur-univax!ning    Mar 17 11:12:00 1985

In my previous article to this newsgroup, I gave details on how to build a
cable between a Mac and a modem.  Fortunately, that worked with my modem;
unfortunately, it doesn't necessarily work with modems that expect a "Data
Terminal Ready" as jsp@unccvax said in his/her reply to my article. Jsp
was correct in saying that my cable might not work with modems that expect
a DTR.  And mine had the option set to ignore the DTR.

I didn't realize that the cable wouldn't work until I tried to attach a
hard-wired Unix on the other end of the cable.  The problem was that the
Unix's serial ports expected a DTR and a "Request to Send" from the Mac,
and the Mac doesn't send any of these signals.

The solution that I found was to trick the Unix by "bouncing" the signals
sent by Unix back to itself.  Since the serial port on the Unix was wired
as "Data Communications Equipment," it sent the signals "Data Set Ready"
and "Clear to Send."  In RS-232 convention, these signals are analogous to
the "Data Terminal Equipment" signals of "Data Terminal Ready" and
"Request to Send."  The point of this is that I could "trick" the Unix
into thinking that my Mac was ready to accept data by sending the DSR back
into the DTR, and the CTS back into the RTS.  So whenever the Unix was
ready to send data, it would find that the Mac was ready to accept; and
whenever it was ready to accept data, it would find that the Mac was ready
to send.

This usually works, but sometimes this faked handshaking might pose a
problem. (In my case, both the Mac and Unix were ready to accept data
anyway.)  But without another kludge, the Mac can't make use of these
signals even if the Unix depended upon them:  Some mainframes that don't
use X-ON and X-OFF (DC1 & DC3 by other names) might use DSR and CTS to
tell the Mac that it is not ready to accept data.  The kludge is to wire
one of these signals (depending on how your mainframe's serial ports
toggle these signals) into the Mac's Carrier Detect, and with software the
uses the Carrier Detect, you get one-way handshaking.

So the forged handshaked, which is what I use for both the hard-wired
serial ports and my modem looks like this:

	Macintosh	Modem		RS-232 Signal Name
	(9-pin DTE)	(25-pin DCE)

Pin #	3	<--->	7		Signal Ground (GND)
	5	---->	2		Transmit Data (TxD)
	9	<----	3		Receive Data (RxD)
	7	<----	8		Data Carrier Detect (DCD)
		 +---	6		Data Set Ready (DSR)
		 +-->	20		Data Terminal Ready (DTR)
		 +---	5		Clear to Send (CTS)
		 +-->	4		Request to Send (RTS)

The one way handshake (which I haven't tried, but in theory should work)
is like the forged handshake with this exception:

		    	6		DSR
	7 HSC	<---<	or
			5		CTS

Now that you see the big mess of RS-232, you can see why people prefer
to use X-ON and X-OFF--that is, until they have to enable and disable it
in order to use XMODEM with macput and macget.

--

Happy happy Telecommunicating,
John Lam_____________________
{allegra,seismo,inhp4}!rochester!ur-univax