Some help hacking up some old hardware I've found.

Some help hacking up some old hardware I've found.

Post by John Oyl » Tue, 16 Jul 2002 10:22:00



Guys,
        I've come across a weird piece of hardware, and usually by this time,
I've taken the heat gun to it in an attempt to salvage any cool IC's I
might come across. However, this one does attempt to power up, and is
particularly interesting.

Central to the mainboard, is a MC68331 variant. I've dabbled with 68ks
before, assembler on an old 68000 mac and amiga, stuff like that. But
this cpu is a stranger to me... is it a member of the CPU32 family
that is hinted at in my old 68k books?

Also, on the board, there is a 2x5 .100" header. I've only been able
to follow one trace, which seems to lead to the 68331. There are 2
other traces that I can be sure of, but they lead off to a couple of
resistors, or so it would appear. Is this a JTAG interface?(The 4th
necessary trace might be hidden, I can't tell) I've done some
research, and the '060 seems to have a builtin jtag, but no other
motorola cpu's seem to have them.

But more intriguing, seems to be 4 sets of pads that surround the
'331. Each set is fine pitch, what appears to be 25 pins to the inch,
in an 2x18 arrangement. Surface mount. Naturally, some pins seem to be
empty, but most lead directly to the '331s pins. Some sort of factory
test ports, meant to have connectors soldered to them?

Finally, if I'm not totally offbase on all of this, and it is a JTAG
connector, will I be able to do anything with it? (Like read the
firmware on the device, since I don't have a programmer that can dump
it... and masked roms aren't worth keeping if you can't do that)

Thanks,
John O.

 
 
 

Some help hacking up some old hardware I've found.

Post by Eric Doenge » Tue, 16 Jul 2002 15:36:42


[ ... ]

Quote:> Central to the mainboard, is a MC68331 variant. I've dabbled with 68ks
> before, assembler on an old 68000 mac and amiga, stuff like that. But
> this cpu is a stranger to me... is it a member of the CPU32 family that
> is hinted at in my old 68k books?

Yes, the 68331 has a CPU32 core.

Quote:> Also, on the board, there is a 2x5 .100" header. I've only been able to
> follow one trace, which seems to lead to the 68331. There are 2 other
> traces that I can be sure of, but they lead off to a couple of
> resistors, or so it would appear. Is this a JTAG interface?(The 4th
> necessary trace might be hidden, I can't tell) I've done some research,
> and the '060 seems to have a builtin jtag, but no other motorola cpu's
> seem to have them.

No, it's not JTAG (which the CPU32 does not have), but probably BDM,
which is Motorola's debugging interface for the CPU32 (stands for
"background debugging mode" AFAIK). In order to use it, you will need
a BDM interface (there are several freely availible schematics
floating around the net) and a de* or something similar to drive
it (for Linux you could use gdb-5.1.1 with bdm patches).

[ ... ]

Quote:> Finally, if I'm not totally offbase on all of this, and it is a JTAG
> connector, will I be able to do anything with it? (Like read the
> firmware on the device, since I don't have a programmer that can dump
> it... and masked roms aren't worth keeping if you can't do that)

If it is a BDM port (and it does sound like it, because a 2x5 header
is standard for BDM), you can access any memory that the 68331 can.

 
 
 

1. Hacking Old Macs...

Hi,

I just acquired a bunch of old 68K Macs (LC,LCII) and was wondering if
anyone had tried to replace the Mac system PROMs in these machines with
more traditional bootproms that support serial based debugging and
downloading ? I know NetBSD and Linux run on the LCIIs, but I think
both require MacOS for booting.

Are schematics easy to get for the system boards ?

Seems like these would be fun machines to play around with for various
controller projects.

See ya, -ingo
--

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