Bill Studenmund writes:
>
>Howdy!
>
>The new version of the serial driver might be done soon, and I'd like to
>get it to work with some of Apple's low-end laser printers. Mainly the
>ones which you have to turn off in order to get NetBSD to boot.
>
>Unfortunately I don't have one of these, so I can't figure out what's
>wrong, though I think I know. So I need other people to help. I need
>either someone who can find jucy technical info from the printer manual,
>or someone with either an oscilliscope or a logic analyser.
>
>Basically, I think these printers are sending the Mac a reference clock
>so the Mac can send data to the printer faster. I need confirmation.
>Also, I need to know how the data speed compares with the clock speed
>(if the data's at 230 k baud, is the clock at 230 kHz, or at 3.6 MHz?).

Hmm...

I ran into a possibly related problem trying to get my StyleWriter
driver (which currently works with the old StyleWriter 1) to work with
the Color StyleWriter 2400.  Basically, talking to the printer over the
serial port from a userland program causes the machine to hang when the
printer should start sending data back.  Unplugging the serial cable
causes things to start happening again for a few seconds, but the
machine hangs again a short time later.  Rebooting without unplugging
the cable also causes the machine to crash again sometime during the
boot sequence.

(BTW, this thing has some wierd energy-saving behavior.  It turns
itself off after being idle for a certain amount of time, and turns
itself on again when it starts getting serial data.  It might make
sense for such a beast to only start up an external clock signal when a
print job starts, I suppose...)

If the StyleWriter were pulling the same trick as these laser printers,
could it cause the symptoms I described?

Unfortunately, I don't have access to anything like an oscilliscope
that I could use to look into this.  If I can compile -current kernels,
is there anything I can do to find out if this might be my problem?
(i.e. do you have test code you could send me that would tell us
anything useful?)

I do have the Zilog book on the SCC.  I'll take a look at it when I get
home and see if it says anything about external clock signals.  It may
be that the chip necessarially defines the way they work.

-- monroe
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Monroe Williams                                      monroe@teleport.com