🚀 go-pugleaf

On Fri, 30 Oct 2009 10:23:51 +1100, the renowned "David L. Jones"
<altzone@gmail.com> wrote:

>Mark Harriss wrote:
>> DJ Delorie wrote:
>>> "David L. Jones" <altzone@gmail.com> writes:
>>>> http://www.youtube.com/watch?v=3YUvlrVlNao
>>>
>>> Sigh, I've been in that type of meeting before.  Not as Mr Head, of
>>> course.
>>
>>
>> What's the PIC architecture like these days?, I heard it was always
>> pretty messy in terms of memory and a real pain to program in
>> assembly.

There are really several PIC architectures.. the 12-bit instruction,
(PIC16F54, PIC12F509 etc.) the 14-bit instruction (most other PIC16F,
16 bit instructions (PIC18) (PIC17 is a dead end), the PIC24/DSPIC,
and the PIC32. They've also extended the instruction sets in a couple
of families. The 12-bit type is the most limiting, but also the most
parsimonious with resources. Even C can't hide the ugliness there, but
in most cases you won't notice or care because the tasks are
relatively simple. For example, IIRC constant arrays can't exceed a
page in size (256 bytes).  

>Tons better.
>They have the PIC18 series which is more C friendly than the old 16 series, 
>the 16 bit PIC24 series which is quite nice, and the new 32 bit PIC32 series 
>based on a MIPS 4K core. Plus the dsPIC too.
>And why would you want to program in assembler anyway for all but niche 
>areas?

IThe PIC18 is quite pleasant to program in assembler... just use
access ram for everything you can, and you don't have to think much
about banking. About the only thing I miss is an indexed plus offset
addressing mode, and I think they have that in the extended
instruction set mode, but I have not played with that (there are some
trade-offs or it would not have to be another mode). 

As to the C vs. asm question.. well, if you have to have a USB or
Ethernet (or Bluetooth) stack then you're in C territory. For less
than 16 k bytes of program memory, assembler probably deserves a look,
especially if you're not doing C-like things. And it depends on the
skill set and prior experience the programmer has, as well as whether
it's worth wringing out what is usually a << 2:1 improvement in
program memory size and performance. 

>Even the old 16 series is not messy if you use a good C compiler, it takes 
>care of any issues for you.
>
>Dave.

The Hitech C compiler (even the free 'lite' one) works pretty well,
though I've found some irritating bugs. It will even generate useful
code for the 12-bit instruction chips. 


Best regards, 
Spehro Pefhany
-- 
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