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From: Chuck Simmons
Organization: You jest.
X-Mailer: Mozilla 4.61 [en] (X11; U; Linux 2.0.33 i586)
Subject: Re: DSP 2's complement vs straight binary
References: <3DAF907C.54D0567F@webaccess.net> <firstname.lastname@example.org>
Date: Fri, 18 Oct 2002 05:16:24 GMT
NNTP-Posting-Date: Thu, 17 Oct 2002 22:16:24 PDT
> >Chuck Simmons email@example.com
> >Thomas Magma wrote:
> >> Ya, I don't know what Analog is trying to say there but I'm sure that
> >> inverting the MSB does not convert straight binary to 2's complement. I
> >> my books at works but here is what I could quickly find on the net to prove
> >> my point.
> Perhaps I am having a senior moment or 2's complement has acquired a new
> I learned 2's complement to do subtraction by an add operation (hardware
> To get 2's complement you invert the entire word -- not the high order bit.
> So if you want to subtract 3 from 5
> 5d-> 0101b -> 2's complement 1010b
> 3-> 0011b
> add 1010b + 0011b = 1101b
> ->1101b -> 2's compliment again 0010b ->2 decimal
> and 5-3=2
You unkindly deleted the table I laboriously created with my ten
incredibly nimble thumbs. However, reference to that table will quickly
show that the column of signed decimal numbers I gave converts using 2's
complement exactly to the column of 2's complement numbers obtained from
the original binary column by means of inverting the MSB. The method is
used for A/D and D/A converters where the mid binary code corresponds to
the common mode or zero.
I note that John Larkin has concluded that you can lead a horse to water
but you can't make him drink.
... The times have been,
That, when the brains were out,
the man would die. ... Macbeth
Chuck Simmons firstname.lastname@example.org
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