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CPSR_c CPSR_x CPSR_s CPSR_f 分别代表什么

时间:2014-03-07 04:23:18      阅读:696      评论:0      收藏:0      [点我收藏+]
CPSR_c CPSR_x CPSR_s CPSR_f 分别代表什么
c 控制域 (PSR [7:0]) 
x 扩展域掩码 (PSR [15:8]) 
s 状态域掩码 (PSR [23:16]) 
f 标志域掩码 (PSR [31:24]) 



MSR
Load specified fields of the CPSR or SPSR with an immediate constant, or from the contents of a general-purpose register.

Syntax   MSR{cond} psr_fields, #imm8
MSR{cond} psr_fields, Rm 
Description   Load fields of the Program Status Register with an immediate constant or register content. 
psr is either CPSR or SPSR.

fields specifies a mask for the Program Status Register and can be one or more of the following:

c control field mask byte (PSR [7:0]) 
x extension field mask byte (PSR [15:8]) 
s status field mask byte (PSR [23:16]) 
f flags field mask byte (PSR [31:24]) 
 Note

In user mode, only the condition flags of the CPSR (CPSR_f) can be changed. In other modes, the entire CPSR can be changed. 
The T bit must never change, otherwise the processor enters an unpredictable state. 
The SPSR register that is accessed depends on Operating Mode (current setting of the mode bits in PSR). 
R15 cannot be used as Rm 
 
Condition Flags   If CPSR_f is specified flags are explicitly updated, otherwise condition flags are unchanged.  
Example       MSR  CPSR_f,R5
 
参考 
1、《ARM instruction set user‘s guide》


CPSR_c CPSR_x CPSR_s CPSR_f 分别代表什么,布布扣,bubuko.com

CPSR_c CPSR_x CPSR_s CPSR_f 分别代表什么

原文:http://blog.csdn.net/inurlcn/article/details/20648679

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