[fpc-devel] cortex-m0 support

David Welch dwelch at dwelch.com
Thu Jan 5 03:35:37 CET 2012

With the cortex-m0 parts now hitting the market I think it is time to 
bring up the topic of thumb support again, not arm not thumb2 but thumb 
(the only common instruction set across almost the entire arm family 
(the exception being the pre-armv4t)).

cortex-m0 and -m1 are armv6-m based, the -m3 and -m4 are armv7m based.

I count something like 20 armv6m instructions that are not in the all 
thumb variants category.  something like 148 armv7m that are not 
supported by armv6m nor all thumb variants.  Just a rough count.

This is why you will see folks saying that the cortex-m0 and -m1 are 
thumb only not thumb2.

The cortex-m0 based mbed's have hit the street btw, available at 
sparkfun and other places.  Note that gcc and llvm fail to build working 
code for the cortex-m0, when you specify cortex-m0 you get thumb2 code 
which fails miserably.


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