Michael Rigby-Jones wrote:
>> 32-bit may provide for quicker development if you want to write in C
>> (and there's talk of C++ at Microchip) but at the most basic level
>> the ALU of a 32 bit chip is always going to be switching more gates
>> than one with fewer bits, thus using more energy per cycle, if you
>> care about battery life.
>
> But a calculation can likely be completed in fewer cycles, especially
> if it involves values larger than 8 bits, and multiple bit shifts etc.

That may be true for some cases, but not most I think.  Having a 32 bit ALU
is good when you're banging around data that really is 32 bits wide.  Most
things microcontrollers do is rather mundane management.  Sure there is som=
e
math on data, but most of the cycles are bumping counters, checking flags,
saving and restoring interrupt state, grabbing data from a hardware
register, bumping a index, checking for wrap, decrementing the loop counter
and checking for done, jumping back to the top of the loop, etc.

When your inputs are 10 or 12 bit A/D readings and your outputs 10 bit PWM
periods, even 16 bits is enough for most data values.

If speed of the math operations isn't a issue, then using multiple cycles i=
n
the relatively rare case when you're doing 32 bit math and using less power
the rest of the time is a win.


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