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Programmer’s Model

ARM7TDMI Data Sheet

ARM DDI 0029E

3-7

Open Access

• THUMB state LR maps onto ARM state R14

• The THUMB state Program Counter maps onto the ARM state Program

Counter (R15)

This relationship is shown in ➲

Figure 3-5: Mapping of THUMB state registers onto

ARM state registers

Figure 3-5: Mapping of THUMB state registers onto ARM state registers

3.7.4 Accessing Hi registers in THUMB state

In THUMB state, registers R8-R15 (the

Hi registers

) are not part of the standard

them, and can use them for fast temporary storage.

A value may be transferred from a register in the range R0-R7 (a

Lo register

) to a Hi

instruction. Hi register values can also be compared against or added to Lo register

values with the CMP and ADD instructions. See ➲

5.5 Format 5: Hi register operations/

branch exchange

on page 5-13.

R10

R11

R12

Stack Pointer (R13)

Link Register (R14)

Program Counter (R15)

Stack Pointer (SP)

Link Register (LR)

Program Counter (PC)

CPSR

SPSR

THUMB state

ARM state

R4R4

Lo registersHi registers

1 2 ... 28 29 30 31 32 33 34 35 36 37 38 ... 41 42

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ARM ARM7TDMI Scheda Tecnica Pagina 33