[fpc-devel] More on arm4, armi and thumb

[Marco van de Voort]

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> On 11/1/07, Marco van de Voort <marcov at stack.nl> wrote:
> > So it seems you only have to do something special for ARMI (vs ARM4) if you
> > do thumb?
> 
> My current theory is that the user library present on my phone is
> built for thumb. So, when a pure arm4 application tryes to access it,
> it crashes.
> 
> The armi application would succed.

It seems that when you branch, in the instruction you can encode if the
 instructionset of the target is thumb or not.

>From my Arm architecture manual (2nd ed) :

The BX (Branch and Exchange) instruction branches to an address held in a
register Rm with an optional switch to thumb execution.

Architecture :v5+ and T versions of v4.

If you want more stuff looked up, yell.