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Re: How to access to Open Firmware via Null-modem?

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@localhost>
To: port-macppc%NetBSD.org@localhost
Subject: Re: How to access to Open Firmware via Null-modem?


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

have fun

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.
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