Em 15/2/2010 14:44, sergio masci escreveu:
>
> On Mon, 15 Feb 2010, Isaac Marino Bavaresco wrote:
>
>   =

>> There is an interesting implementation which is used by MPLAB-C18
>> library (file itobcd.asm).
>> It is a very efficient serialized method, it uses only shifts and adds.
>> It is worthy a try.
>>     =

> Hi Isaac,
>
> Thanks for the pointer but in this case I was trying to explain the =

> fundamentals and in particular why getting to grips with 16 bit arithmati=
c =

> on an 8 bit PIC is a GOOD thing. The whole thing would have been really =

> trivial had the OP been comfortable with 16 bit arithmetic in the first =

> place.
>
> Regards
> Sergio Masci
>   =



I understand, but this method doesn't use 16-bit math at all. All the
math is done nibble-by-nibble, no carry is propagated during the additions.
The only part that uses carry propagation is during the shifts, that
shifts the whole 16-bit (or 9-bit in this case) value. It works for
values with any number of digits.

If you don't already know this method, I would suggest to study it, it
is very enlightening. Shows a very different approach that exploits
curious properties of binary and BCD numbers. It is being used for a
while by the CPLD/FPGA guys, because it is easily implemented using just
shift-registers and adders.


Best regards,

Isaac
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