SUMMARY: Default serial speeds - how to change (late...)

From: Hans C Larsson (
Date: Sun Dec 06 1992 - 09:39:57 CST

A while ago I asked the net how to change the *default*
serial line speed on Sun's.

I was having problem connecting to an old Hidem 2400 modem.

If I disabled the DTR-pin in the modem a connection could
be made but this has some disadvantages (e.g the modem doesn't
see when the line process exits).

My idea was that when carrier was established (DCD) the getty(8)
would open the port, the kernel would change the line speed,
and the ol' Hidem would be "upset" and hang up.

Further testing concluded that the problem was the V.42bis/MNP
negotiation from the calling ("modern") modem.
If I disabled that (with various Hayes-commands) the connection
worked out fine.

However, I still don't know why disabling the DTR-pin could
help ??!!

However again, I received one reply on how to change the default
speed (in the kernel) from " (Jim Thompson)".

His reply below for interested adb(1)'ers :-)

B9600 is '13', so what you need to do is look for a instruction
that loads a '13' into a location that later gets used in the
context of 'zsopen()'.

Look at location zsopen+0x10c (sun4c,SunOS4.1.2), it should be a
instruction like:

        _zsopen+0x10c: mov 0xd, %i4

I forget what it would look like on a motorola box, and I don't
have one here.

If you get to a call to 'zsgetspeed' you're not quite far enough, if
you get to a call to 'zsparam', you've gone too far.

        Hans C Larsson			Email:
	Saab Missiles, Sweden		Motto:	"keep it short"

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