14 Feb
2008
14 Feb
'08
5:56 p.m.
Date: Thu, 14 Feb 2008 13:01:04 -0500
From: Dave McGuire
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.
On the other hand, the PIC1640, developed for the CP1600 in 1976 is
clearly recognizable as a cousin to the modern PIC, right down to the
W register.
The odd thing was that the PIC1640 used a 12-bit instruction word,
while the CP1600 used 10 bits of the instruction word, even though it
was a 16-bit CPU. The CP1600 wasn't particularly deficient in I/O
operations--it simply didn't have any. Couple that with a 1MHz clock
and multi-word instructions and you had a very slow system, even
compared to a 2MHz 8080. On the other hand, the instruction set was
very pleasant and fairly orthogonal--it might remind one of a PDP-11
instruction set.
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.
Cheers,
Chuck