🚀 go-pugleaf

In a recent article by brianw@microsoft.UUCP (Brian Willoughby):
>I've been interested for some time in getting a simple DSP board up and
>running in my Apple II Plus.  Please don't laugh, I would basically be
>using the Apple as a source of power and a cheap interface to a SCSI hard
>disk.  Since the 56000 host interface is 8 bits anyway, this seems like
>a feasable project.  Anyone have any experience with designing for the
>56000 from the ground up?

In my spare time I've designed a 56K based system that resides on a board
for the PC/AT family.  Layout/design for the chip is fairly trivial, so long
as you are conservative in calculating external I/O and RAM/ROM access times
(i.e. don't skimp).  Fast static RAMs (such as the 16KX4 and 64KX4 parts) are
relatively inexpensive, and their prices are dropping rapidly.  My first proto
was wire-wrapped, and I suggest that you take great care in layout if this
is the method you wish to use.  Use bypass caps liberally.

>I realize that assembling programs would be difficult without a
>cross-compiler that would run on the Apple itself.  I do have a full C
>compiler which claims System 5 library compatibility.  Does anyone know
>of a simple 56000 cross-assembler, perhaps from Motorola?

One of the advantages in using the PC (or the Mac II, for that matter) is
the relatively cheap assembler/simulator available from Moto.  The C compiler,
though far from bug-free, provides a very useful algorithm prototyping
enviroment, and is also available from Moto.  After designing the structure
of the program in C, you can hand optimize (through in-line assembly), as well
as write time-critical sections in assembly.

As far as using the Apple II for this purpose, I can't say that I would
really recommend it unless you can find a PD assembler.  Writing an assembler
for the chip is non-trivial, since the 56K is more of a microcode engine
than a `regular' microprocessor (this is a positive attribute in my opinion,
however one must accept the differences).  I hope you can find something, but
I wouldn't count on it (let me know if you do).

Good luck with your project!

Mike
Tektronix, Inc.
mhorne@ka7axd.wv.tek.com

Michael T. Horne                                      VSG/ITD, Tektronix, Inc.
mhorne@ka7axd.wv.tek.com                                        (503) 685-2077