Re: NOPs, odd bits, timings

[Wayne Morellini <waynem1@xxxxxxxxxxxxxxxxx>]

>Christophe Lavarenne <Christophe.Lavarenne@inria.fr> wrote:
>
>> The inversion of odd address and data bits is rather confusing.
>
>No more than the conversion between binary/hex/decimal.
>The confusion maybe comes from the way some cross-compilers are written.
>Forget bit inversions until you want to transfer your cross-compiled code/data
>to real memory, and only at that moment invert odd data and address bits.
>A compiler run by the MuP21 itself does not have to care about bit inversions,
>exactly as you don't care the voltage encoding of bits on other processors.
>The only moments when you have to care is when you are accessing external I/O,
>or when you are looking at the MuP21 pins with a scope.

So what you are saying is that:
- Bit inversion does not effect instructions like and, or, +, -, as it is
invisible to them.

- But bit inversion does have the effect when you hook something up to the
i/o bus, Data Bus or Address Bus, of inverting the odd pins.

This has been my understanding of it.

I heard that they didn't have to do it anymore and that future chips could
do withoout it, is this right?

Thanks Christophe.

Wayne.

>
>CL
>


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