f28m35 m3单步调试成功，断点和全速调试出现硬foult，求助

出现硬foult后，我查了下Hard Fault Status：HFAULTSTAT=0x6000_0000，Configurable Fault Status ：FAULTSTAT=0x0002_0000，按这个错误提示好像是EPSR中的THUMB位改变了引起的硬件foult。但是在调试的时候THUMB一直是1。

THUMB 1          EPSR Thumb State. This bit indicates the Thumb state and should always be set. The following can clear the THUMB bit:
                                • The BLX, BX and POP{PC} instructions
                                • Restoration from the stacked xPSR value on an exception return
                                • Bit 0 of the vector value on an exception entry
                         Attempting to execute instructions when this bit is clear results in a fault or lockup. See “Lockup” on
                         page 116 for more information.
                          The value of this bit is only meaningful when accessing PSR or EPSR.

上面这段是EPSR.THUMB位的说明，难道用了BLX,   BX,     POP{PC}都会出现这个问题，那不是子程序都返回不了了？