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Wed, 06 Jun 2007

Locking in SuperH.


Shame on me, I did not mention tas.b instruction, which does exactly what is needed for spinlock implementation - it reads a byte, specified in register, then sets a bit in the returned value, and writes it back. If value read is zero, special bit is set. All operations are performed with locked bus, so it is atomic.
I read description for that instruction many times, but failed to translate or understand. But, whatever it was, spilocks are pefectly valid on SH-4 family, so it would be possible to create SMP system, since I even found multiprocessor serial communication in 7750R, which allows to transfer data between multiple CPUs, where each receiver is addressed via unique ID.

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