CPSR有4个8位区域：
标志域（F）、状态域（S）、扩展域（X）、控制域（C）
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>, #immed_8r MSR{cond} <psr>_<fields>, Rm where: cond is an optional condition code. <psr> is either CPSR or SPSR. <fields> specifies the field or fields to be moved. <fields> can be one or more of:
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]).
immed_8r is an expression evaluating to a numeric constant.
The constant must correspond to an 8-bit pattern rotated by an even number of bits within a 32-bit word. Rm is the source register.
C 控制域屏蔽字节(psr[7:0])
X 扩展域屏蔽字节(psr[15:8])
S 状态域屏蔽字节(psr[23:16])
F 标志域屏蔽字节(psr[31:24])
常用于MRS或MSR指令,用于psr中的值转移到寄存器或把寄存器的内容加载到psr中.
如:
msr cpsr_c,#0xd3 @进入管理模式
msr cpsr_c,#0xd2 @ 进入中断模式