CoreMP7

10

v2.6

The Relationship Between ARM State and Thumb State Registers

The Thumb state registers relate to the ARM state registers in the following way:

•

Thumb state r0–r7 and ARM state r0–r7 are identical.

•

Thumb state CPSR and SPSR, and ARM state CPSR and SPSR are identical.

•

Thumb state SP maps onto ARM state r13.

•

Thumb state LR maps onto ARM state r14.

•

The Thumb state PC maps onto the ARM state PC (r15).

These relationships are shown in Figure 6.

Note: Registers r0–r7 are known as the low registers. Registers r8–r15 are known as the high registers.

Figure 6 •

Mapping of Thumb State Registers to ARM State Registers

Thumb State

r0

r1

r2

r3

r4

r5

r6

r7

r8

r9

r10

r11

r12

Stack Pointer (r13)

Link Register (r14)

Program Counter (r15)

Current Program Status Register

(CPSR)

Saved Program Status Register

(SPSR)

r0

r1

r2

r3

r4

r5

r6

r7

Stack Pointer (PC)

Link Register (LR)

Program Counter (PC)

Current Program Status Register

(CPSR)

Saved Program Status Register

(SPSR)

ARM State