如果说 ARMv7-M 的不同特性, 它们或许暗示着:
(1) SP, LP, PC currently is specail register for v7M instead of using as general purpose registers sometimes under v5 Architecture.
(2) xPCR only manage APSR, IRSP and EPSR, which is different from v5 (it will save any PSR with every proess mode).
(3) Add MASK and CONTROL registers. About Control register, we found it should be specail for us to know the privilege mode, sp mode and fp extension.
尽管有这两者我们总结出的上述不同, 但是也让我们感觉到了 arm architecture 的继承性.