BX - Branch and Exchange

Syntax

BX[condition] dest

where:

condition	One of 16 conditions. Refer to Condition Code Status.
dest	Destination register

Description

The BX instruction branches to the specified dest containing an ARM* or Thumb* instruction and optionally executes it. To select an ARM instruction bit[0] of the destination register needs to be set to 0. To select a Thumb instruction bit[0] of the destination register needs to be set to 1. The condition needs to be a valid value; else the instruction is rendered an NOP.

Addressing Mode

No operands.

Flags Affected

N	Z	C	V	Q	S	I	F	T
T	T	T	T					M

Encoding

31		28	27	26	25	24	23	22	21	20	19		16	15		12	11		8	7	6	5	4	3		0
condition			0	0	0	1	0	0	1	0	SBO			SBO			SBO			0	0	0	1	dest_ addr

Example

1                          ;@.text
2
3                          ;@.globl funcbx
4
5                          ;@.align 0
6
7                          ;@ * * * BX * * *
8
9
10                     AREA example, CODE, READONLY
11                     label1
12   00000000   E3A0B001   MOV   R11, #1
13   00000004   E2AB0001   ADC   R0, R11, #1
14   00000008   E4107000   LDR   R7, label2
15
16   00000012   E12FFF17   BX    R7
17
18   00000016   E3A0B001   MOV   R11, #1
19   00000020   E21B0001   ANDS R0, R11, #1
20
21                     label2
22                         DCD   0xdeadbeef
23                         DCB   "string"
24
25                         END   26