15 Feb
2008
15 Feb
'08
9:54 a.m.
On Feb 14, 2008, at 8:56 PM, Chuck Guzis wrote:
Are they really that bad? How so?
Doubtful,
as it's just the same architecture, and far from the
same implementation. The 8X30x chips are bipolar, if memory
serves. But
either way, I'm not sure what the point would be, aside from
possibly
building new boards using an existing 8X30x MSCP implementation.
As one who has had the extreme displeasure of programming both the
8X300 and an 8X305, I'd have to say that the two have about as much
in common with a PIC as a pocket knife to an CNC EDM system. The
instruction sets aren't even close, nor is the data path
architecture. In some respects, the bipolar chip has a bit more
flexibility (e.g. variable-length operations and an "execute"
instruction) even with its limitation of an instruction set of size
8.
...
Do you have a cite that states that the PIC1640 is a
direct
descendent of the SMS 300? Microchip certainly doesn't admit it--and
I'd be hard pressed to find the similarity beyond both being Harvard
architecture binary CPUs.
I went to gather references and I found that I may have
misunderstood something a very long time ago! Here's a quote from
the PIC FAQ:
The roots of the PIC originated at Harvard university
for a Defense
Department project, but was beaten by a simpler (and more reliable
at the time) single memory design from Princeton. Harvard
Architecture was first used in the Signetics 8x300, and was adapted
by General Instruments for use as a peripheral interface controller
(PIC) which was designed to compensate for poor I/O in its 16 bit
CP1600 CPU. The microelectronics division was eventually spun off
into Arizona Microchip Technology (around 1985), with the PIC as
its main product.
I (more than a decade ago) took that to mean that the processor
architecture (the instruction set and register layout, not just
"Harvard") was traced back to the 8X300. It was *Harvard
architecture* that was used by GI, not the 8X300 architecture...does
that make more sense? In that case, I stand corrected and apologize
for my error!
That said, what can you tell us about the 8X30x processors? I
don't think I've ever known anyone else who designed with them.
-Dave
--
Dave McGuire
Port Charlotte, FL