Laptop User Manual

THUMB INSTRUCTION SET S3C2440A RISC MICROPROCESSOR
4-16
FORMAT 6: PC-RELATIVE LOAD
15 0
0
14
10
[7:0] Immediate Value
[10:8] Destination Register
Word 8
00
13 12
11
Rd0 0
87
Figure 4-7. Format 6
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.
Table 4-7. Summary of PC-Relative Load Instruction
THUMB assembler ARM equivalent Description
LDR Rd, [PC, #Imm] 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.
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 Word 8. 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.