今天看porteus官网，对M3内核支持还不完善啊

2019-08-16 18:50发布

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The following is a listing of known limitations in the current version of the ARM® Cortex™-M3:

Bitband alias regions are of type XN (Execute Never).
Cache information is not used.
Systick calibration value register (SYST_CALIB) is ignored.
Data Barrier instructions (DMB,DSB) are treated as NOP.
Register PLLCFG is not modelled.
Clock Verification Timers and Internal brown-out detector not modelled.
Registers DR2R,DR4R,DR8R,SLR are not modelled.
Loopback feature of the I2C Module is not documented and therefore not modelled.