Subject:
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RE: H8 & unaligned word accesses
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Newsgroups:
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lugnet.robotics
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Date:
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Tue, 11 May 1999 15:52:08 GMT
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Viewed:
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976 times
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Brain wrote:
> > Right you are Matt. This created a bit of trouble when I was
> > porting the original
> > pbFORTH code over to the H8. I THINK this is because the H8
> > core is extensible
> > to a full 16 bit machine - or even 32. The "8" in H8 is a
> > misnomer except at
> > the bottom end of the family where we are, of course, stuck.
>
> I am currently using the H8S/2144 processor at work. The above statement is
> totally correct - the H8 series is directly compatible with the 16-bit H8S
> series. Because the H8S is a true 16 bit processor, internal memory is
> always accessed as a word (16 bits). Now it is possible with some of the
> instructions to do byte wide manipulations, and it is even possible to load
> and store single bytes (even or odd addresses). However, every word access
> must be word-aligned. When you use Hitachi's E6000 in circuit emulator,
> there is a feature that breaks whenever you access an odd address. This
> allows you to debug your code that otherwise would just assume that the
> lowest address bit is 0 and keep marching on like nothing's wrong.
Brian, how does the rest of the Hitachi H8 line stack up? Up until now, I
have been using Motorola exclusively, except for the odd PIC design and
even a 4 bit NEC 75000 series design!!!
The Hitachi gnu chain seems pretty decent, even the simulator worked well
enough for me to get the RCX running without much crash and burn coding...
It's a neat part, so far - I think the LEGO designers must have had a pretty
big decision to make since so much of the MIT work was based on Motorola
processors.
Have you tried pbFORTH yet?
Cheers,
Ralph Hempel - P.Eng
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Check out pbFORTH for LEGO Mindstorms at:
<http://www.bmts.com/~rhempel/lego/pbFORTH/default.html>
--------------------------------------------------------
Reply to: rhempel at bmts dot com
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Message is in Reply To:
 | | RE: H8 & unaligned word accesses
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| (...) I am currently using the H8S/2144 processor at work. The above statement is totally correct - the H8 series is directly compatible with the 16-bit H8S series. Because the H8S is a true 16 bit processor, internal memory is always accessed as a (...) (25 years ago, 11-May-99, to lugnet.robotics)
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