s3c2410a Samsung Semiconductor, Inc., s3c2410a Datasheet - Page 87

• Manufacturer Part Number: s3c2410a
• Description: 16/32-bit Risc Arm Microprocessor
• Manufacturer: Samsung Semiconductor, Inc.

S3C2410A
BRANCH AND EXCHANGE (BX)
This instruction is only executed if the condition is true. The various conditions are defined in Table 3-2.
This instruction performs a branch by copying the contents of a general register, Rn, into the program counter, PC.
The branch causes a pipeline flush and refill from the address specified by Rn. This instruction also permits the
instruction set to be exchanged. When the instruction is executed, the value of Rn[0] determines whether the
instruction stream will be decoded as ARM or THUMB instructions.
INSTRUCTION CYCLE TIMES
The BX instruction takes 2S + 1N cycles to execute, where S and N are defined as sequential (S-cycle) and non-
sequential (N-cycle), respectively.
ASSEMBLER SYNTAX
BX - branch and exchange.
BX {cond} Rn
{cond}
Rn
USING R15 AS AN OPERAND
If R15 is used as an operand, the behavior is undefined.
31
Cond
Two character condition mnemonic. See Table 3-2.
is an expression evaluating to a valid register number.
28
27
0 0
[3:0] Operand Register
If bit0 of Rn = 1, subsequent instructions decoded as THUMB instructions
If bit0 of Rn =0, subsequent instructions decoded as ARM instructions
[31:28] Condition Field
0
24
1
Figure 3-2. Branch and Exchange Instructions
23
0 0
1
20
0
19
1 1
1
16
1
15
1 1
1
12
1
11
1 1
1
1
8 7
0 0
0
ARM INSTRUCTION SET
1
4 3
Rn
0
3-5