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From: drew@cup.portal.com (Andrew E Wade)
Newsgroups: comp.sys.mac
Subject: Re: best deal on new/used 2400 baud Mac-compatible modem?
Message-ID: <22896@cup.portal.com>
Date: 8 Oct 89 21:37:11 GMT
References: <459@janus.UUCP> <6651@hubcap.clemson.edu>
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Organization: The Portal System (TM)
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>Ok, so MNP slows down interactive.  Is it possible to turn it off, via
>hardware or software?

>John Yen  (RSVP to robert@toaster.sfsu.edu; this is a friend's account.)

Answer:  sure.  Here's how (caveat:  I don't claim, expertise in datacomm;
just read the manual and tried it; also, although I think the MNP commands
are standardized, like the rest of the AT commands, I certainly don't know
for sure and haven't tried this except on Practical Peripherals and Macs).

To make it act like Hayes modem, I do
AT&F&D3L1&W
where &F means reset to factory specs (which is non-RELiable mode)
	&D3 allows it to be interrupted by call waliting (which I like)
	L1 lowers speaker volume; obviously not critical...
	&W saves it in eprom so when you power down modem it remember it

To make it use the MNP error correction and compression, I do:
AT&FL1&D3\N3\J0\Q1\C2\T60%A13&W
where	&F as above, for clean, known starting state
	&D3, L1 as above (and not really relevant)
	&W as above, and important
	\N3 turn on auto-reliable mode
	\J0 turn off bps adjust, so link between computer and modem can be
		different from modem-modem link, with buffering; e.g., former
		might be 9600 baud, while later is 2400 baud.  I'm guessing
		this is critical for compression, since less data goes
		modem-to-modem.  Some computer/software combinations might
		have trouble with this (red ryder and quickmail seem to 
		understand it; netserial doesn't).  It might be possible to
		run without this, but I didn't figure it out.
	\Q1 means use sw xon/xoff (^s/^q) flow control.  Some flow control is
		probably necessary for buffered mode (see \J0).  \Q3 means
		hw flow control, which might be better if your hw has it.
	\C2 means that if this is the receiving modem, and if the caller
		sends the character specified in %A command (carriage return),
		then don't go through the 4 second attempt to estable a
		RELiable connection.  That means that non-MNP modem calling
		up to this modem force it to behave like non-MNP, without
		an annoying 4 sec delay.  This works fine.  We have both
		kinds of modems (modi?) calling.  If modem reports
		CONNECT 2400 it's normal (non-REL or non-MNP) connection,
		while CONNECT 2400/REL means MNP or RELiable connection.
	\T60 is really irrelevant:  it means that if the line is innactive
		for 60 minutes, modem should automatically hang up.
	%A13 (see \C2 above) means <CR> is the character that, when received,
		tells the receiving MNP modem that caller is non-MNP.  This
		works well because most callers/scripts include <CR>.
For the callee modem you might well want to set it to auto-answer (S0=1 to
answer on first ring).
To see all non-MNP status, do AT&V
To see MNP status, do AT\S.  If it reports DIR \N1, it's acting non-MNP.
If it reports AUT \N3, it's acting REL.

Again, no warranties of any kind, but above seems to be working fine for us.
I'm curious about (don't understand) several things:  \G (flow control between
computer and modem); \L (stream vs. block mode -- can it be used if modem
is used interactively?  must it be used to get speed advantage over non-MNP
for batch transfers?  seems inconvenient to have to turn this on and off).
I tried \J1, which forces computer-modem serial speed to be same as
modem-modem (2400 in my case), and it did seem to work, though presumably would
slow down transfer of compressed data, hoping that it would speed up the
interactive stuff, but no luck.
\N0 might be useful when you know you're calling a non-MNP modem, but I didn't
try it.

Also, I don't understand why they don't just put in a one-pager with above
cookbook settings.  Instead I had to pour througha 162-page manual!  Can you
believe it!

All the other registers were fine in their default settings.  Here's a summary:
(output of at\s command, which shows all MNP-special settings):
at\s

IDLE
MODEM BPS	2400	AT
MODEM FLOW	OFF	AT\G0
MODEM MODE	AUT	AT\N3
AUTO ANS.	OFF	ATS0=0		[set to S0=1 for auto-answer]
SERIAL BPS	9600	AT		[or higher if your modem/sw handles it]	
BPS ADJUST	OFF	AT\J0
SERIAL FLOW	X-ON	AT\Q1
PASS XON/XOFF	OFF	AT\X0
PARITY		8N	AT		[8 bits,no parity,1 stop bit is common]
BREAK		5	AT\K5
EXIT CHAR	043	ATS2=43
CMD ECHO	ON	ATE1
RESULTS		ON	ATQ0

  - STRIKE ANY KEY TO CONTINUE -

RESULT TYPE	LONG	ATV1\V0
DATA ECHO	OFF	AT\E0
INACT TIMER	060	AT\T60
CMPRESSION	ON	AT%C1
MAX BLK SIZE	64	AT\A0
AUTO BUFF	2	AT\C2
AUTO CHAR	013	AT%A13
MNP BLOCK	OFF	AT\L0
PAUSE TIME	002	ATS8=2
DTR		3	AT&D3
CARR DET	0	AT&C0
SPEAKER CTRL	1	ATM1
LEASE LINE	OFF	AT&L0
DIAL MODE	4	ATX4
PULSE DIAL	US	AT&P0
GUARD TONE	0	AT&G0
BELL		ON	ATB1

drew@objy.com