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 14:52:19 GMT
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Original-From:
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Brian Schmalz <BRIAN.S@LOGICPD.nomorespamCOM>
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Reply-To:
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<brian.s@logicpd.com%stopspammers%>
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Viewed:
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839 times
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> 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.
Anyway, some technical gobledy-gook always does the reader good. So there
you have it.
*Brian Schmalz
Embedded Systems Engineer
Embedded Logic
Minneapolis, MN
--
Did you check the web site first?: http://www.crynwr.com/lego-robotics
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Message has 1 Reply:
 | | RE: H8 & unaligned word accesses
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| (...) 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 (...) (25 years ago, 11-May-99, to lugnet.robotics)
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Message is in Reply To:
| | RE: H8 & unaligned word accesses
|
| (...) 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 (...) (25 years ago, 11-May-99, to lugnet.robotics)
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