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Re: Big-Endian vs. Little-Endian

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And?

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It may be intuitively clear, but for what purpose?  How
often do you wish to address the LSbyte of a multi-byte
value?

Re: Big-Endian vs. Little-Endian


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I do it all of the time, but I don't see having it at
the same address as the longword as being any intuitively
clearer. In fact, I find the opposite to be slightly more
intuitive.

How about 4-bit processors?  I am sure that I am not
the only one here who like them...  Any opinions about
Big-Endian vs. Little-Endian when using multiple nybbles
to make bytes?
 


Re: Big-Endian vs. Little-Endian
Everett M. Greene ??:
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network packets' header use the bigedian, but no need to call converting
fuctions to convert the value in packet header if use bigedian machine

BZ


Re: Big-Endian vs. Little-Endian
Usually the processor manufacturer made the choice for you
by implementing the instruction set. Even for 8bit machines.

Rene
--
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& commercial newsgroups - http://www.talkto.net

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Re: Big-Endian vs. Little-Endian
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You've missed the point that some processors can be used in either big
or little endian mode.

--
Paul Black                        mailto: snipped-for-privacy@oxsemi.com
Oxford Semiconductor Ltd          http://www.oxsemi.com
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Re: Big-Endian vs. Little-Endian

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Yes, but many of these have a prefererance for one mode.  The PPC
architecture, for example, perfers big-endian - some implementations (like
the MPC56x) don't support little-endian at all, while those that do have
certain restrictions - I believe the string instructions only function in
big-endian mode, for example.  This is because all cpus have are
fixed-endian at heart (normally big- or little-endian, though there have
historically been computers with all sorts of arrangements), and the
non-native mode is handled using thunking - the bytes of multi-byte data are
re-arranged on the fly as data is moved into and out of the cpu.




Re: Big-Endian vs. Little-Endian
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The one I'm most familar with is the ARM where the endianness is set by
an external line.


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CPUs internally have no endianness. The endianness only comes into play
when accessing memory.


--
Paul Black                        mailto: snipped-for-privacy@oxsemi.com
Oxford Semiconductor Ltd          http://www.oxsemi.com
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Re: Big-Endian vs. Little-Endian
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Now that you're talking about the question I raised, which
choice do people make when they have a free choice?

Re: Big-Endian vs. Little-Endian
On Mon, 23 Aug 2004 08:09:25 PST, snipped-for-privacy@mojaveg.iwvisp.com (Everett

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The issue is so low down in the priority list that I can't imagine a
situation where the endianness of the processor would make the
difference, unless there was something in the application itself that
made one choice or the other preferable for compatibility with other
components of the system.



-Robert Scott
 Ypsilanti, Michigan
(Reply through this forum, not by direct e-mail to me, as automatic reply
address is fake.)

Re: Big-Endian vs. Little-Endian

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Do processors with high end at the lower address tend to have a more
regular instruction set than the reverse persuasion? I'm thinking of the
Motorola mindset (6800, 6803, 6809 of blessed memory, 68000) v the
nightmares of 8085/Z80/80x86. In the days when I used to write a lot of
assembler, I know which ones I preferred!

Paul Burke


Re: Big-Endian vs. Little-Endian

[...]
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The VAX was _very_ regular (too regular for its own good), and was
little-endian.

The AVR is little-endian.  

Regards,

                               -=Dave
--
Change is inevitable, progress is not.

Re: Big-Endian vs. Little-Endian
On Mon, 23 Aug 2004 08:09:25 PST, snipped-for-privacy@mojaveg.iwvisp.com (Everett

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The only application we've found where endianness might matter
is for a comms stack where the protocol defines data to be in
a particular (usually big-endian) format. In practice, this
has very little impact on performance. For example, in a TCP/IP
stack, checksum generation is far more important than the
impact of endianness.

Stephen
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Stephen Pelc, snipped-for-privacy@INVALID.mpeltd.demon.co.uk
MicroProcessor Engineering Ltd - More Real, Less Time
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Re: Big-Endian vs. Little-Endian
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And then there is the USB, which is little-endian.
IIRC, at least one of the descriptors has unaligned
members as well.


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Michael N. Moran           (h) 770 516 7918
5009 Old Field Ct.         (c) 678 521 5460
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Re: Big-Endian vs. Little-Endian
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USB was originally described by Intel, so what would you
expect?

Did you ever get the feeling that the first Little-Endian
machine was a mistake and rather than correct the error,
it was decided to market it as a FUG?  [FUG = "it's a
feature, not a bug"]

Re: Big-Endian vs. Little-Endian
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Oh ... I got what I expected ;-)

[Off-topic]
In all fairness, however, I think that much of the
USB design is quite good. In particular, the various
service types (bulk,interrupt,control,isochronous)
are IMHO, well considered. I find it "funny" that most
vendors (or is it their engineering staff) use bulk
transport for almost everything, even when there are
more appropriate mechanisms. I suspect it is because
of familiarity with the operation of UART serial ports
that the USB is to replace.

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For better or worse, business decisions rule. It's a
money thing ... I wouldn't understand ;-)

--
Michael N. Moran           (h) 770 516 7918
5009 Old Field Ct.         (c) 678 521 5460
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Re: Big-Endian vs. Little-Endian

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The one that matches the byte-order of I/O devices, for example.

--
Wil

Re: Big-Endian vs. Little-Endian
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When dealing with bitstreams such as raster lines, big-endian is
way better. The ultimate machine for these apps have large words
and are big-endian.

Bulk operations such as applying masks are not affected, but some
operations such as shifting, shearing, and bit-bending are way
easier on a natural order machine when having to cast around
types.

I say natural order - maybe that should be anthropic order. We read
numbers LtoR, MSD to LSD.

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Re: Big-Endian vs. Little-Endian
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Do you have troubles reading a UART stream from a scope then ?
A minimum of flexibility is expectable from people working
embedded...

Rene
--
Ing.Buero R.Tschaggelar - http://www.ibrtses.com
& commercial newsgroups - http://www.talkto.net

Re: Big-Endian vs. Little-Endian
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Can you say "non sequitur"?


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Re: Big-Endian vs. Little-Endian
On Tue, 24 Aug 2004 05:10:25 GMT, Bryan Hackney

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Latin for "it does not follow."

Except it does.  If you look at the serial stream from a UART on a
scope, the bits appear left to right, LSb to MSb.  And depending on
where you hook into the circuit, ones may be low and zeros high.  Does
take some getting used to.

OTOH, if the serial stream is an ASCII text string, it DOES tend to be
transmitted leftmost character first...

Regards,

                               -=Dave
--
Change is inevitable, progress is not.

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