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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
register set. However, the assembly language programmer has limited access to
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
register, and from a Hi register to a Lo register, using special variants of the MOV
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.