LDM 和STM编码时有一个参数P,官方文档里的解释如下:
P==1
indicates that the word addressed by Rn is included in the range of memory locations accessed, lying at the top (U==0) or bottom (U==1) of that range.
P==0
indicates that the word addressed by Rn is excluded from the range of memory locations accessed, and lies one word beyond the top of the range (U==0) or one word below the bottom of the range (U==1).
我理解是P==1时为类似空栈的方式( Rn指的内存单元将会被使用 )
P==0时为类似满栈的方式( Rn指的内存单元将不会被使用 )
可是我又发现当LDMIA时显示P==0 (INCREASE AFTER,类似空栈)
LDMIB时P==1(INCREASE BEFORE,类似满栈)
越看越晕,不知道到底是怎样了,请大家释疑,谢谢 |
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