ST STM32H7 Series User Manual

The STM32 Cortex-M4 instruction set PM0214
80/262 PM0214 Rev 9
Restrictions
In these instructions:
• Do not use PC.
• Do not use SP for Rd and Rt.
• For STREX, Rd must be different from both Rt and Rn.
• The value of offset must be a multiple of four in the range 0-1020.
Condition flags
These instructions do not change the flags.
Examples
MOV R1, #0x1 ; initialize the ‘lock taken’ value try
LDREX R0, [LockAddr] ; load the lock value
CMP R0, #0 ; is the lock free?
ITT EQ ; IT instruction for STREXEQ and CMPEQ
STREXEQ R0, R1, [LockAddr] ; try and claim the lock
CMPEQ R0, #0 ; did this succeed?
BNE try ; no – try again
; yes – we have the lock
3.4.9 CLREX
Clear Exclusive.
Syntax
CLREX{cond}
Where:
‘cond’ is an optional condition code (see Conditional execution on page 65)
Operation
Use CLREX to make the next STREX , STREXB , or STREXH instruction write 1 to its destination
register and fail to perform the store. It is useful in exception handler code to force the failure
of the store exclusive if the exception occurs between a load exclusive instruction and the
matching store exclusive instruction in a synchronization operation.
See Synchronization primitives on page 34 for more information.
Condition flags
These instructions do not change the flags.
Examples
CLREX

ST STM32H7 Series Specifications

General

Brand	ST
Model	STM32H7 Series
Category	Computer Hardware
Language	English

Summary

About this document

Typographical Conventions

Defines formatting used in the document for clarity.

List of Abbreviations for Registers

Provides a list of abbreviations used in register descriptions for quick reference.

STM32 Cortex-M4 Processor Overview

Introduces the STM32 Cortex-M4 processor's architecture and key features.

The Cortex-M4 Processor

Programmer's Model

Describes registers, modes, and privilege levels for software execution.

Memory Model

Details the processor's memory map, access behavior, and bit-banding features.

Exception Model

Explains exception states, types, priorities, and handling mechanisms.

Fault Handling

Covers fault types, escalation, status registers, and lockup conditions.

Power Management

Describes mechanisms for entering and exiting low-power sleep modes.

The STM32 Cortex-M4 Instruction Set

Instruction Set Summary

Lists supported Cortex-M4 instructions and their organization.

Memory Access Instructions

Details instructions for loading and storing data from/to memory.

General Data Processing Instructions

Explains instructions for arithmetic, logical, and data manipulation.

Multiply and Divide Instructions

Describes instructions for multiplication and division operations.

Floating-Point Instructions

Details instructions for FPU operations, including VFPv4-SP extension.

Miscellaneous Instructions

Covers instructions like breakpoints, barriers, and supervisor calls.

Core Peripherals

About the STM32 Cortex-M4 Core Peripherals

Introduces the core peripherals accessible via the Private Peripheral Bus (PPB).

Memory Protection Unit (MPU)

Explains the MPU for memory region definition and access control.

Nested Vectored Interrupt Controller (NVIC)

Describes the NVIC for managing interrupts and exceptions with priority levels.

System Control Block (SCB)

Details registers for system control, configuration, and exception reporting.

SysTick Timer (STK)

Explains the 24-bit SysTick timer for system timing and RTOS ticks.

Floating Point Unit (FPU)

Describes the FPU for single-precision floating-point operations.

Revision History