[ell-i-developers] Re: Instructions before asynchronous exception

  • From: Pekka Nikander <pekka.nikander@xxxxxx>
  • To: ell-i-developers@xxxxxxxxxxxxx
  • Date: Wed, 5 Feb 2014 07:38:36 +0200

> I am trying to find out how many instructions can be executed between an 
> asynchronous exception is triggered and the handler is entered (for making 
> sure that the behaviour of PendSV is the desired one, as at some point we 
> will use blocking synchronization primitives)

My suggestion would be to use a synchronous interrupt for entering from a 
blocking primitive, e.g. SVCall.  Remember too that if we don't have a separate 
user mode and supervisor mode, it may be sufficient just to block the 
interrupts and do the thing there, on the spot, not to separately enter an 
interrupt routine through a vector.  That would save a number of cycles as 
well, making the primitive faster.

> For Cortex M-0, i can't find it... Does anyone know about any reference or 
> document where it can be found, just to speed up the searching process?

At least I don't know, but hopefully someone else does?


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