Re: TI MSP430



On 15 Apr 2006 18:29:50 +0100, David Brown
<david@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote:

CBFalconer wrote:
David Brown wrote:
... snip ...
What is much more relevant is whether the register set and
addressing modes of the msp430 really are appropriate for their
target applications, or whether they would have been better off
with the PDP-11 arrangement. I'm far from convinced - certainly,
the example you gave (PC-relative CALL) is obscure indeed, and I
think the benefit of more registers well outweighs this missing
feature.

Hardly obscure. This, together with PC relative jumps, is what
makes object code intrinsically relocatable, and I consider it a
valuable feature. Now it becomes trivial to swap code segments in
and out as needed.


In terms of the PDP-11 (did it count as a mini or a mainframe?), making
code position independent and/or relocatable is important, and greatly
adds to the flexibility of the architecture. In terms of a small
embedded processor, running a single statically linked program with no
paging or other virtual memory arrangements, relocatable or position
independent code is irrelevant,
<snip>

It shocks me to read this from you. It is patently untrue in the case
of the MSP-430. Position independent code is important in this case,
as it enables a number of useful options. One of them is being able
to download small "programs" into the ram, allowing the downloader to
place them as the memory allocator allows, and to execute them.
Another is to allow flashable extensions to be downloaded.

If you need objective evidence, beyond my own theory about this, you
need only note that IAR already supports the production of position
independent code to a degree and is involved in broadening out that
capability in the case of the MSP-430. That fact speaks for itself.

So you have both theory and practice to dispute your comment.

Jon
.