I use 38400 8N1 /TYPICALLY/ some four-fingered salutes will return the 
mobo to its factory condition. I think 7 rounds of Meta+Alt+P+R clears the 
PRAM of ALL settings. (Including current date/time and total uptime, on 
some (?all) systems.) Then the meta+alt+O+F should put you at the prompt. 
feq counters, silly-scopes can help narrow it down, or a pair of 
headphones if you are really really good.

For The Record: My e250s have two single-channel DB25 DTE sockets.

Also for the record:

Remember the Mac has differential RS422 (or better) signaling that 
garantees voltage relative to ground at the transmitter,good for backwards 
compatability OR long distance+highspeed.

You probably want to ground the common ground on the Mac (PIN 4), the TX+ 
and the RX+ to the signal ground of the RS232 jack AT the rs232 jack (PIN 
7 if DB25) (running all three gets better signal) twist the tx pair and 
the rx pair for echo cancelation. Ground the shell ("pin 0") to the shell 
using an non-twisted conductor.

Use the least number of non-soldered connections; if you can make your own 
cables, then do so!


bonne chance!


On Tue, 1 Jan 2008, Jdrm wrote:

> Date: Tue, 1 Jan 2008 08:28:17 -0800 (PST)
> From: Jdrm <jacobo.da.riva@gmail.com>
> To: port-macppc@NetBSD.org
> Subject: Re: How to access to Open Firmware via Null-modem?
> 
>
> Hi
>
>
>
> Use ttya ( should be labeled 'modem' or something like that ) on the
> mac, make sure to disable any handshaking on the PC.
>
>> I've do something similar with a Sun's Enterprise 250 and works fine!
>
> What kid of cable did you use? One intended for Macs or Suns or
> something completely different? Macs serial ports are different from
> Sun and SGI ones even though they're using the same connector and the
> data lines are on the same pins - everything else, like handshake for
> instance - is different. So if you configured hardware handshake it
> will stall. If you configured software handshake you'll likely get
> funny results since OpenFirmware doesn't enable it and I'm not sure
> it even supports it.
> Play a little bit with your terminal settings, early Apple OF doesn't
> always behave logically or as documented.
>
> Finally, I dimly remember using 57600kBit/s but that might be a wrong
> memory.
>
> have fun
> Michael
>
>
> -- 
> I've different cable to connect to Sun E250 and to connect to Mac.
>
> The mac adapter is connected from ttya (the connector with a modem) to the
> serial in my PC (Debian). No one software are using that port. I use minicom
> to connect via modem.
> I'm testing different configurations in minicom (from 9600 kBit/s to 576000)
> but i don't have any signal from the Mac. I'll trying again.
> -- 
> View this message in context: http://www.nabble.com/How-to-access-to-Open-Firmware-via-Null-modem--tp14566316p14567831.html
> Sent from the port-macppc mailing list archive at Nabble.com.
>