Sean Alcorn - Avion Sydney wrote:
>
> Hi Guys,
>
> I am just about to embark on my next project, and am in the planning stages.
>
> Whilst I understand the difference between BCD and straight binary, I am a
> little confused about what actually determines whether a value is stored as
> BCD or straight binary.
>
> For example, the command;
>
> RETLW    99
>
> Would return the value 99 as BCD in W right?

Nope. The value '99' that the assembler will read is dependant on the
RADIX setting at the time of assembly. Usually this defaults to HEX.

So RETLW 99 would generate 0x3499 as the HEX code, or return with 0x99
in W. (153dec)

If the RADIX is decimal then RETLW 99 will generate 0x3463, or return
with 0x63 in W. (99dec)


> But what about;
>
> RETLW    255
> or
> MOVLW   99
> or
> MOVLW    255
>
> Obviously the 255 gets stored as straight binary, but how is that 'decision'
> made? Is 99 the maximum for BCD?

Same rules apply.

The PIC doesn't work directly with BCD numbers and you would have to
write code that handles them yourself.

The RADIX can be set manually in your code using the RADIX command, or
by setting it in the pop-up screen that appears when you assemble the
asm file.

--
Best regards

Tony

mICros
http://www.bubblesoftonline.com
mailto:sales@bubblesoftonline.com

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