Earlier today, I wrote:

> the PIC16's Carry flag is actually a combination of the Cout bit
> and an internal "overflow" bit... This means that, after an
> addition or subtraction, you can use the state of the Carry flag as
> an under/overflow indicator.

    Please forget that I said that... It's not accurate.  Everything
    else in that message is fine, though.

    Also, Jonathan King suggested reading the following two articles:

> "A minus B = A + not(B) + 1 (Part 1)" EDN Dec 5 1996, p199-204
> "A minus B = A + not(B) + 1 (Part 2)" EDN Jan 2 1997, p119-128

    I took Honathan's advice and read those articles today... They're
    pretty good.  The author doesn't explain two's-complement math in
    much detail, but he does give an interesting overview of ALU
    design.

    -Andy

=== Andrew Warren - fastfwd@ix.netcom.com                 ===
=== Fast Forward Engineering - Vista, California          ===
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