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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: <firstname.lastname@example.org> <email@example.com> <3DAF907C.54D0567F@webaccess.net>
Date: Fri, 18 Oct 2002 04:55:34 GMT
NNTP-Posting-Date: Thu, 17 Oct 2002 21:55:34 PDT
Chuck Simmons wrote:
> 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 left
> > my books at works but here is what I could quickly find on the net to prove
> > my point.
> Binary MSB inverted Binary value MSB inverted as 2's comp value
> 111 011 7 3
> 110 010 6 2
> 101 001 5 1
> 100 000 4 0
> 011 111 3 -1
> 010 110 2 -2
> 001 101 1 -3
> 000 100 0 -4
> That looks right to me.
I forgot to mention that in a micro, you can sign extend and convert to
2's complement with a subtract. The three bit binary above sign extends
to 8 bits by subtracting 100. You can sign extend with an add of
11111100 as well but the status register negative bit will be wrong.
... 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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