--- allisonp <allisonp_at_world.std.com> wrote:
> >[ Its the chip used in the Apple Lisa and Mac and LOTS of other devices. ]
>
> You sure of this?? It's not really friendly to the 68k buses.
>
> Allison
I'm sure. It's in the Mac from day one, in Sun workstations since at least
the Sun3 era (and still in one form or another in various sun4c boxes) and
in every 68K-based product Software Results made after the Unibus products
(the original boards used the COM5025 like the DEC DPV11? DUV11?)
I will admit that it is not friendly to the MC68K bus. We used one or two
dedicated PALs to handle the interfacing. Additionally, we had an 8Mhz CPU
(10Mhz for the VAXBI model), but back when the Z8530 was new, 4Mhz parts
were available and later some 6Mhz, but 8Mhz parts didn't come along until
way later, long after our designs were done. There's lots of notes in the
COMBOARD source code about not wacking on the Z8530 too fast. Eventually,
we developed a kind of serial driver to handle swabbing registers, but the
first products just used macros to always space out the time between telling
the Z8530 which internal register to select and reading/writing that register.
Personally, I think it's a cool chip, much cooler than the 8250/16450/16550
family. In addition to an async console for debugging, we pumped 3780, HASP
and SNA traffic over them up to 128Kbps (our fastest modem eliminator speed).
We only ever sold products for use at 56Kbps (64Kbps in Europe).
-ethan
=====
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Received on Fri Jun 02 2000 - 00:43:43 BST