[PD] Re: [PD-dev] small gizmos

Martin Peach martinrp at vax2.concordia.ca
Fri Sep 10 19:32:22 CEST 2004


I'm not sure the PIC is the best choice here, because it has separate 
data and program memory: you can't execute code that resides in RAM. The 
only way it will work is as a byte-by byte interpreter I'm starting to 
think the ST7 would be better here:
http://www.st.com/stonline/products/support/micro/st7/st7lite.htm
It has a very similar architecture and instruction set to the 65XX 
series, it's even cheaper than most PICs. I'm only starting to read the 
docs but it seems that you could download small blocks of code and have 
them execute in RAM using a bootstrap loader (at least I haven't found 
where it says that you can't do so). Using a PIC you would need to 
preprogram all possible routines and use selector bytes to call them as 
needed, as in a BASIC interpreter.
Martin


Tom Schouten wrote:

>On Thu, Sep 09, 2004 at 08:54:25AM +0200, Tom Schouten wrote:
>  
>
>>i just stumbled on the (or part of) the solution for the
>>pic bootstrap interpreter here:
>>
>>in fact this illustrates that the idea is not exactly new.
>>
>>    
>>
>
>sorry, url was this:
>http://pygmy.utoh.org/3ins4th.html
>
>also check this:
>http://www.forthfreak.net/wiki/index.cgi?ForthScripts
>
>btw, pygmy forth itself (for DOS and also some ARM dev board)
>is a nice example of a self-contained forth written in forth
>with a built in block editor.
>
>i'm not a big fan of block editors, except for the one
>in ColorForth, but it's a nice piece of forth history.
>
>cheers
>tom
>
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