ARM9 mode of operation, register, addressing mode

Working mode

A RM has 7 Modes of Operation :

Name	Referred	Brief introduction
User	U SR	The normal User program execution mode (Linux under the user program is executed in this mode.) ）
FIQ	F IQ	Fast Interrupt Mode
Irq	I RQ	Normal Interrupt Mode
S Upervisor	S VC	A mode that gives the operating system the protection mode, the privilege is high, the Linux kernel is running in this mode
A bort	A BT	For example, access to virtual memory, resulting in an exception, is to enter this mode.
U ndefined	U nd	Running a command that is not supported by a processor goes into this mode.
S ystem	S Ys	A rmv4 and above version only. Use less.

Register Device

the registers have a total of 37 x , 31 Universal registers, 6 status registers. The approximate structure is as follows, a total of 18, not enough 37, the remainder is actually the register of the banked, in different modes, the packet register and the program status register with different physical registers.

Below two

The following two registers require special attention:

R13 for Stack Register

R14 for LR Register

With regard to the program status Word register in arm, he is equivalent to the status Word register in M3, interrupt screen register, control register, and some of its more important bits are described below:

The N and z bits represent the state of the result of the operation, the comparison jumps, and the conditional execution instructions are used to get them.

The I and f bits are controls for fast interrupts and normal interrupts.

m[] bit is the control of the operation mode and the use of the banked register.

Note: CPSR and SPSR content is the same, but SPSR can be used as an archive for CPSR, Rough said: That is, before entering other modes to save the contents of CPSR in SPSR, after the return of CPSR after the value has been destroyed, but can be SPSR reply.

addressing mode

aRM has 5 ways of addressing, as follows:

immediate number addressing

Register Addressing

Register Indirect Addressing

base Address variable address addressing

relative addressing

From for notes (Wiz)

ARM9 mode of operation, register, addressing mode