Hi Russell,

At 05:58 PM 7/1/99 +1200, you wrote:
>>* As we've discussed before, the PIC architecture is
>>exceedingly beginner-friendly.
>
>I'd disagree. For the "hello world" stuff its oK but I think it's
>arcane as you write bigger programs after other more "linear" address
>space devices - it does however give you excellent code compactness
>as a result. PIC also suffers from having grown from a very very old
>design - the double barrel roll required to save context on interupt
>is bizarre and is a clear product of not having to do this
>way-back-then when there were no interupts. I appreciate MChips
>desire to make code backward c ompatible but Scenix seems to have
>addressed this very nicely (I haven't USED Scenix personally yet) by
>providing a basic context save on interupt. Also, adding things like
>a real stack in some versions would allow upwards migration while
>allowing older code to run transparently.
>

I have worked with several micros but the PIC has definately been the one I
have done the most work on. SO, as a result, I have a question about
typical micrcontroller architecture: how many microcontrollers operate at a
constant number of cycles per instruction (except branches)? I find this to
be a real time saver. I have written a fair amount of code for the 68000
series,and I am glad I never had to try to write something isochronous or
an exact delay.

I have also seen some of the MIPS architecture (which, I guess, is as flat
RISC as it gets) but I wonder how many micros in the same class as the
PIC(available in flash and with a small pin count and built-in
peripherals), but which include the features that you want (a real stack,
linear addressing, etc.), also have the constant number of cycles per
instr? Yes, I know that the SX and AVR do, but they don't have a real stack
and linear addressing, do they? (I am familiar with the SX, but not yet
with the AVR)




Sean


|
| Sean Breheny
| Amateur Radio Callsign: KA3YXM
| Electrical Engineering Student
\--------------=----------------
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