CSL中定义的这三个宏我一直不太理解：
1.CSL_<MODULE>_<REG>_SHIFT
The number of left shift positions to reach the register bit-field of interest
2.CSL_<MODULE>_<REG>_MASK
The binary *and* mask useful to extract register bit-field of interest
3.CSL_<MODULE>_<REG>_RESETVAL
The power-on reset value assumed by the register or bit-field of interest
RESETVAL好像是RESET后寄存器的值，那MASK和SHIFT到底是什么含义？用途是什么？
还有文档中的解释里每句最后的of interest到底是什么意思？谢谢！
