Great explanation of PIC types, Bob!

--Bob


At 05:42 AM 11/26/2003, you wrote:

>All PICs address data memory 8 bits at a time. Instructions vary in width
>based on the series. Wider width allows more RAM to be addressed in each
>'bank' and more versatile instructions.
>
>PIC12 program port very easily to PIC16. Mostly the PIC16 is a direct
>superset of the PIC12. Instructions in the PIC12 are 12 bits each, in the
>PIC16 they are 14 bits. Note that some small PICs that are labeled PIC12 are
>really PIC16 inside. RAM banks are 16 bytes each.
>
>PIC17 is basically a forgotten attempt at an improvement on the PIC16.
>Although there are many applications using it (included MChips' own PicStart
>Plus), few people would choose it for a new design. It is again possible to
>port from the PIC12 or PIC16 to the PIC17. The PIC17 uses 16 bit
>instructions. RAM banks are 128 bytes each.
>
>PIC18 is a very large improvement over the three prior series. It was
>designed to more readily support C compilers. Porting from PIC12 or PIC16 to
>PIC18 is pretty straightforward. It is a little trickier moving from the
>PIC17. In all cases, there are some gotchas regarding what happens to flags
>on certain instructions. Like the PIC17, the PIC18 uses 16 bit instructions.
>RAM banks are 256 bytes each.
>
>Note that all cases of 'porting' require modifying the source code and
>rebuilding the executable.
>
>Bob Ammerman
>RAm Systems
>
>--
>http://www.piclist.com#nomail Going offline? Don't AutoReply us!
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--------------
Bob Axtell
PIC Hardware & Firmware Dev
Tucson, AZ
1-520-219-2363
"I lose some on each sale but make it up in volume."

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