ARM7TDMI Datasheet, PDF (122/268 Pages) List of Unclassifed Manufacturers – general purpose 32-bit microprocessors

THUMB Instruction Set
5.6 Format 6: PC-relative load
15 14 13 12 11 10 9
8
76
5
4
3
2
1
0
01 0 0 1
Rd
Word8
Immediate value
Destination register
Figure 5-7: Format 6
5.6.1 Operation
This instruction loads a word from an address specified as a 10-bit immediate offset
from the PC.
The THUMB assembler syntax is shown below.
THUMB assembler
LDR Rd, [PC, #Imm]
ARM equivalent
Action
LDR Rd, [R15, #Imm]
Add unsigned offset (255 words,
1020 bytes) in Imm to the current
value of the PC. Load the word
from the resulting address into Rd.
Table 5-7: Summary of PC-relative load instruction
Note
Note
The value specified by #Imm is a full 10-bit address, but must always be word-aligned
(ie with bits 1:0 set to 0), since the assembler places #Imm >> 2 in field Word8.
The value of the PC will be 4 bytes greater than the address of this instruction, but bit
1 of the PC is forced to 0 to ensure it is word aligned.
5-16
ARM7TDMI Data Sheet
ARM DDI 0029E