From: Bruce Boyes Systronix <bboyes@sy...> - 2000-11-06 00:16:52
Michael Schmitt wrote:
> Has anybody some experience with the new Dallas CPU 89C420 ? I am a bit
> confused about the In System Programable functionality.
Yes, we are using it. Sort of. There are some significant errata in the
current silicon. There is a data sheet link from our web site and also at
Dallas'. Some current samples are available from Dallas but, to be honest,
they are only marginally useful. We're able to make some limited progress
with the current parts. We can run in 8051 compatability mode from external
memory and load a small program in flash.
We're creating a development board which should be available when the
revised silicon is ready. No, I don't know exactly when -- Dallas recently
told us end of Nov.
The part has 16 KBytes of flash and an internal bootstrap loader. You put
the part into a special bootstrap reset mode and talk to the loader. You
can then program the internal flash. There are other ways, too. The two
banks can be ping-ponged, you can execute out of one while programming the
other (you would need some of your own code to do this). The banks can be
swapped so that either bank boots up at internal location 0.
It's a very promising looking part. 50 MIPs is pretty hard to beat. Our
development board will support the 420 page mode 1 out of external memory
for maximum speed. There are a number of subtleties to using the part and
getting the most performance out of it. We'll have boards and documentation
when the revised parts are ready. Dallas will have a special promotional
We have a preliminary C420 page on our website with provision to email you
when the page changes: http://www.systronix.com/c420/c420.htm
We might like to be able to offer sdcc support for the C420 to users of the
board. There are some non-trivial subtleties in using the part in any of
the higher performance modes with external memory. Our development board
and accompanying code will address these. Any interested parties can email
me off-line if interested in working with sdcc on the C420, or stay tuned
to the web site.
- Bruce Boyes
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