PM0214 datasheet(143/245 Pages) STMICROELECTRONICS

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PM0214

The STM32 Cortex-M4 instruction set

244

3.9.6

CBZ and CBNZ

Compare and branch on zero, compare and branch on non-zero.

Syntax

CBZ Rn, label

CBNZ Rn, label

where:

•

‘Rn’ is the register holding the operand.

•

‘label’ is the branch destination.

Operation

Use the CBZ or CBNZ instructions to avoid changing the condition code flags and to reduce

the number of instructions.

CBZ Rn, label does not change condition flags but is otherwise equivalent to:

CMP

Rn, #0

BEQ

label

CBNZ Rn, label does not change condition flags but is otherwise equivalent to:

CMP

Rn, #0

BNE

label

Restrictions

The restrictions are:

•

Rn must be in the range of R0 to R7

•

The branch destination must be within 4 to 130 bytes after the instruction

•

These instructions must not be used inside an IT block.

Condition flags

These instructions do not change the flags.

Examples

CBZ

R5, target ; Forward branch if R5 is zero

CBNZ

R0, target ; Forward branch if R0 is not zero

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