ST STM32F3 Series User Manual

PM0214 Rev 10 79/262
PM0214 The STM32 Cortex-M4 instruction set
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3.4.8 LDREX and STREX
Load and Store Register Exclusive.
Syntax
LDREX{cond} Rt, [Rn {, #offset}]
STREX{cond} Rd, Rt, [Rn {, #offset}]
LDREXB{cond} Rt, [Rn]
STREXB{cond} Rd, Rt, [Rn]
LDREXH{cond} Rt, [Rn]
STREXH{cond} Rd, Rt, [Rn]
Where:
• ‘cond’ is an optional condition code (see Conditional execution on page 65).
• ‘Rd’ is the destination register for the returned status.
• ‘Rt’ is the register to load or store.
• ‘Rn’ is the register on which the memory address is based.
• ‘offset’ is an optional offset applied to the value in Rn. If offset is omitted, the address is
the value in Rn.
Operation
LDREX, LDREXB, and LDREXH load a word, byte, and halfword respectively from a
memory address.
STREX, STREXB, and STREXH attempt to store a word, byte, and halfword respectively to
a memory address. The address used in any store-exclusive instruction must be the same
as the address in the most recently executed load-exclusive instruction. The value stored by
the store-exclusive instruction must also have the same data size as the value loaded by the
preceding load-exclusive instruction. This means software must always use a load-
exclusive instruction and a matching store-exclusive instruction to perform a
synchronization operation, see Synchronization primitives on page 34.
If a store-exclusive instruction performs the store, it writes 0 to its destination register.
If it does not perform the store, it writes 1 to its destination register.
If the store-exclusive instruction writes 0 to the destination register, it is guaranteed that no
other process in the system has accessed the memory location between the load-exclusive
and store-exclusive instructions.
For reasons of performance, keep the number of instructions between corresponding load-
exclusive and store-exclusive instruction to a minimum.
Note: The result of executing a store-exclusive instruction to an address that is different from that
used in the preceding load-exclusive instruction is unpredictable.

ST STM32F3 Series Specifications

General

Series	STM32F3
Core	ARM Cortex-M4
Max CPU Frequency	72 MHz
Operating Voltage	2.0 V to 3.6 V
GPIO Pins	Up to 80
Timers	Advanced-control, general-purpose, basic timers
ADC	12-bit
DAC	12-bit
Communication Interfaces	USART, SPI, I2C, CAN, USB
Operating Temperature	-40°C to 85°C
Package	LQFP, UFQFPN, WLCSP

Summary

Introduction

1 About this document

1.1 Typographical conventions

Conventions used in the document for formatting text and code elements.

1.2 List of abbreviations for registers

Abbreviations used in register descriptions.

1.3 About the STM32 Cortex-M4 processor and core peripherals

Overview of the processor's features and integrated peripherals.

2 The Cortex-M4 processor

2.1 Programmers model

Describes the programmer's model, processor modes, privilege levels, and stacks.

2.2 Memory model

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

2.3 Exception model

Explains the exception model, states, types, handlers, and priorities.

2.4 Fault handling

Details fault types, escalation, status registers, and lockup.

2.5 Power management

Describes mechanisms for entering and waking up from sleep modes.

3 The STM32 Cortex-M4 instruction set

3.1 Instruction set summary

Overview of the instruction set and supported instructions.

3.2 CMSIS intrinsic functions

CMSIS intrinsic functions for generating Cortex-M4 instructions.

3.3 About the instruction descriptions

Explains how instruction descriptions are presented in the document.

3.4 Memory access instructions

Details instructions for accessing memory.

3.5 General data processing instructions

Covers general-purpose data processing instructions.

3.6 Multiply and divide instructions

Describes instructions for multiplication and division operations.

3.7 Saturating instructions

Explains instructions that perform saturating arithmetic.

3.8 Packing and unpacking instructions

Instructions for packing and unpacking data.

3.9 Bitfield instructions

Instructions for operating on bitfields within registers.

3.10 Floating-point instructions

Instructions for floating-point operations using the FPU.

3.11 Miscellaneous instructions

Other Cortex-M4 instructions not categorized elsewhere.

4 Core peripherals

4.1 About the STM32 Cortex-M4 core peripherals

Overview of core peripherals and their memory map in the PPB.

4.2 Memory protection unit (MPU)

Details the MPU's functionality for memory protection and region management.

4.3 Nested vectored interrupt controller (NVIC)

Describes the NVIC's support for interrupts, priorities, and tail-chaining.

4.4 System control block (SCB)

Provides system implementation info and control for exceptions.

4.5 SysTick timer (STK)

Details the SysTick timer, its registers, and usage hints.

4.6 Floating point unit (FPU)

Explains the FPU's functionality, registers, and enabling.

5 Revision history