ARM VERSION 1.2 - Manual (Page 229)

Thumb Instruction Reference
ARM DUI 0068B Copyright © 2000, 2001 ARM Limited. All rights reserved. 5-35
5.4.3 BX
Branch, and optionally exchange instruction set.
Syntax
BX Rm
where:
Rm is an ARM register containing the address to branch to.
Bit 0 of Rm is not used as part of the address.
If bit 0 of Rm is clear:
• bit 1 must also be clear
• the instruction clears the T flag in the CPSR, and the code at the
destination is interpreted as ARM code.
Usage
The BX instruction causes a branch to the address held in Rm , and changes instruction set
to Thumb if bit 0 of Rm is set.
Architectures
This instruction is available in all T variants of the ARM architecture.
Examples
BX r5