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From: amarcum@next.com (Alan M. Marcum)
Newsgroups: comp.sys.next
Subject: Re: Connecting a modem to Next running 2.0
Message-ID: <206@rosie.NeXT.COM>
Date: 22 Jan 91 01:26:58 GMT
References: <7636@plains.NoDak.edu> <1991Jan19.224552.14895@nntp-server.caltech.edu>
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madler@pooh.caltech.edu (Mark Adler) in <1991Jan19.224552.14895@nntp-server.caltech.edu>:
> Also, does anyone know if any Mac's?wire RTS and CTS like the 040 NeXT's.
> Maybe it's not so non-standard.

Last I checked (a few months ago) I found at least six different
"Mac-Modem" cables.  For example, I've seen different cables with one
(or more) of the following:

	Signal	DB-25	MiniDIN
	CTS	5	2
	DSR	6	2
	DTR	20	2
	DCD	8	2
	RTS	4	1

One cable had both DSR and DCD connected to MiniDIN Pin 2.

The specs for a modem cable on both 030 and 040 NeXT machines are to
have DCD, Pin 8 on the DB-25, connected to MiniDIN Pin 2.  In order
for /dev/cua (for example) to work, Pin 2 must see a signal which
reflects the presence or absence of a remote carrier.  Typically, this
will be DCD (assuming correct modem setup).

If you want hardware flow control, I doubt strongly whether you'll
find a Mac-Modem cable which meets NeXT's pin-out specifications.

All this is documented in the UNIX Manual Pages under zs [zs(4) for
the UNIX types], along with the interlocks between cuX (dial-out) and
ttydX (dial-in).  For now, yes, you'll either have to build your own
cable or have a custom cable vendor build it for you.  No, this is not
an ideal situation.

For those wondering, for those without UNIX manual pages available for
our system, here are the modem cable specs from the manual page.  Note
that the zs manual page included in the 2.0 version of the Network and
System Administration Manual is the 1.0, not the 2.0, manual page.
The cable spec in the manual page in the Admin Manual shows the
correct pin-outs for a 68030-based computer (with the caveat the
MiniDIN Pin 2 SHOULD be called DCD, not CTS).  Also, the modem cable
for a 68040-based computer is specified in Chapter 13, Attaching
Peripheral Devices.

	68030-to-modem (no flow control available)
	MiniDIN-8	DB-25
	1 DTR		20 DTR
	2 DCD		8 DCD
	3 TxD-		2 TxD
	4 GND		7 GND
	5 RxD-		3 RxD
	6 TxD+		-not connected-
	7 RTxC/+5V	-not connected-
	8 RxD+		7 GND

(Note that on the 68030-based machines, Port A's Pin 7 is RTxC while
Port B's Pin 7 is +5 volts.)

	68040-to-modem
	MiniDIN-8	DB-25
	1 DTR		20 DTR
	2 DCD		8 DCD
	3 TxD		2 TxD
	4 GND		7 GND
	5 RxD		3 RxD
	6 RTS		4 RTS
	7 RTxC		-not connected-
	8 CTS		7 CTS
-- 
Alan M. Marcum
NeXT Technical Support
amm@NeXT.COM