This device can read from its own FLASH, so it would be possible to
embed two 7-bit characters in each 14-bit program-word and read them back.


Isaac


Em 22/6/2010 14:00, Dwayne Reid escreveu:
> Good day to all.
>
> We've got an existing product where we are now being asked to 
> extend.  I'm trying to avoid PCB changes (for now) because the 
> current layout is certified for use in a hazardous location (Class 1, 
> Div 1, Groups C&D)  and any changes to the layout cost us significant 
> fees for re-certification.
>
> The current PIC is a 16F77 with about 600 words free.  The engineer 
> working on this project estimates that he will need about 1.5 K words 
> - give or take a few.
>
> I see a few options:
>
> 1) Go to a larger PIC that has the same footprint (DIP 40).
>
> 2) Optimize his existing code to make it smaller.  Having seen his 
> code, I'd bet that I can easily squeeze out 20% of space.
>
> 3) Find a better way of dealing with text strings.
>
> I'm leaning in the direction of #3 above.
>
> There is almost 2 K words of text stored in the 8K of program space 
> in the 'F77.  I recall reading about a technique where one can store 
> 2 ASCII chars in each word, then retrieve as needed.
>
> I suspect that I'd have to move to something like the 'F877 but that 
> is no problem.
>
> Any pointers and suggestions gratefully accepted.
>
> Many thanks!
>
> dwayne
>
>   
>
>
>
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