Herbert Graf <PICLIST@MITVMA.MIT.EDU> wrote:

> Sorry for my ignorance, but what is the difference between normal
> carry and digit carry? Can you give me an example of the
> difference.

Herbert:

The digit carry (also called "half carry") is a carry from the lower
nibble of a byte to the upper nibble... That is, from bit 3 to bit 4.
It's sometimes useful for doing packed-BCD arithmetic and other
operations on 4-bit values packed two to a byte.

For example:

    REG contains 0F hex.
    W contains 01 hex.

        ADDWF   REG

    Now REG contains 10 hex, and the digit-carry flag is set.

and:

    REG contains 0E hex.
    W contains 01 hex.

        ADDWF   REG

    Now REG contains 0F hex, and the digit-carry flag is clear.

-Andy


=== Andrew Warren - fastfwd@ix.netcom.com
=== Fast Forward Engineering - Vista, California
=== http://www.geocities.com/SiliconValley/2499