INSTRUCTION SET
S3C4510B
FORMAT 18: UNCONDITIONAL BRANCH
11
10
15
14
13
12
0
Offset11
1
1
1
0
0
[10:0] Immediate Value
Figure 3-47. Format 18
OPERATION
This instruction performs a PC-relative Branch. The THUMB assembler syntax is shown below. The branch offset
must take account of the prefetch operation, which causes the PC to be 1 word (4 bytes) ahead of the current
instruction.
Table 3-25. Summary of Branch Instruction
THUMB Assembler
ARM Equivalent
Action
B label
BAL label (half-word offset) Branch PC relative +/- Offset11 << 1, where label is PC
+/- 2048 bytes.
NOTE: The address specified by label is a full 12-bit two¢s complement address,
but must always be half-word aligned (ie bit 0 set to 0), since the assembler places label >> 1 in the Offset11 field.
Examples
here
B here
; Branch onto itself. Assembles to 0xE7FE.
; (Note effect of PC offset).
B jimmy
...
; Branch to 'jimmy'.
; Note that the THUMB opcode will contain the number of
; half-words to offset.
Jimmy
...
; Must be half-word aligned.
3-94
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