The Definitive Guide to the ARM Cortex-M0

The Definitive Guide to the ARM Cortex-M0 is a guide for users of ARM Cortex-M0 microcontrollers. It presents many examples to make it easy for novice embedded-software developers to use the full 32-bit ARM Cortex-M0 processor. It provides an overview of ARM and ARM processors and discusses the benefits of ARM Cortex-M0 over 8-bit or 16-bit devices in terms of energy efficiency, code density, and ease of use, as well as their features and applications. The book describes the architecture of the Cortex-M0 processor and the programmers model, as well as Cortex-M0 programming and instruction set and how these instructions are used to carry out various operations. Furthermore, it considers how the memory architecture of the Cortex-M0 processor affects software development; Nested Vectored Interrupt Controller (NVIC) and the features it supports, including flexible interrupt management, nested interrupt support, vectored exception entry, and interrupt masking; and Cortex-M0 features that target the embedded operating system. It also explains how to develop simple applications on the Cortex-M0, how to program the Cortex-M0 microcontrollers in assembly and mixed-assembly languages, and how the low-power features of the Cortex-M0 processor are used in programming. Finally, it describes a number of ARM Cortex-M0 products, such as microcontrollers, development boards, starter kits, and development suites. This book will be useful to both new and advanced users of ARM Cortex devices, from students and hobbyists to researchers, professional embedded- software developers, electronic enthusiasts, and even semiconductor product designers.

• The first and definitive book on the new ARM Cortex-M0 architecture targeting the large 8-bit and 16-bit microcontroller market
• Explains the Cortex-M0 architecture and how to program it using practical examples
• Written by an engineer at ARM who was heavily involved in its development

Foreword

Preface

Acknowledgments

Conventions

terms and Abbreviations

Chapter 1 Introduction

Why Cortex-M0?

Energy Efficiency

Code Density

Ease of Use

Application of the Cortex-M0 Processors

Background of ARM and ARM processors

Cortex-M0 Processor Specification and ARM Architecture

ARM Processors and the ARM Ecosystem

Getting Started with the Cortex-M0 Processor

Organization of This Book and Resources

Chapter 2 Cortex-M0 Technical Overview

General Information on the Cortex-M0 Processor

The ARM Cortex-M0 Processor Features

System Features

Implementation Features

Debug Features

Others

Advantages of the Cortex-M0 Processor

Energy Efficiency

Limitations in 8-Bit and 16-Bit Architectures

Easy to Use, Software Portability

Wide Range of Choices

Low-Power Applications

Small Gate Count

High Efficiency

Low-Power Features

Logic Cell Enhancement

Cortex-M0 Software Portability

Chapter 3 Architecture

Overview

Programmer’s Model

Operation Modes and States

Registers and Special Registers

R0━R12

R13, Stack Pointer (SP)

R14, Link Register (LR)

R15, Program Counter (PC)

xPSR, Combined Program Status Register

Behaviors of the Application Program Status Register (APSR)

PRIMASK: Interrupt Mask Special Register

CONTROL: Special Register

Memory System Overview

Stack Memory Operations

Exceptions and Interrupts

Nested Vectored Interrupt Controller (NVIC)

Flexible Interrupt Management

Nested Interrupt Support

Vectored Exception Entry

Interrupt Masking

System Control Block (SCB)

Debug System

Program Image and Startup Sequence

Chapter 4 Introduction to Cortex-M0 Programming

Introduction to Embedded System Programming

What Happens When a Microcontroller Starts?

Designing Embedded Programs

Inputs and Outputs

Development Flow

C Programming and Assembly Programming

What Is in a Program Image?

Vector Table

C Startup Code

Program Code

C Library Code

Data in RAM

C Programming: Data Types

Accessing Peripherals in C

Cortex Microcontroller Software Interface Standard (CMSIS)

Introduction of CMSIS

What Is Standardized in CMSIS

Organization of the CMSIS

Using CMSIS

Benefits of CMSIS

Chapter 5 Instruction Set

Background of ARM and Thumb Instruction Set

Assembly Basics

Quick Glance at Assembly Syntax

Use of a Suffix

Thumb Code and Unified Assembler Language (UAL)

Instruction List

Moving Data within the Processor

Memory Accesses

Stack Memory Accesses

Arithmetic Operations

Logic Operations

Shift and Rotate Operations

Extend and Reverse Ordering Operations

Program Flow Control

Memory Barrier Instructions

Exception-Related Instructions

Sleep Mode Feature━Related Instructions

Other Instructions

Pseudo Instructions

Chapter 6 Instruction Usage Examples

Overview

Program Control

If-Then-Else

Loop

More on the Branch Instructions

Typical Usages of Branch Conditions

Function Calls and Function Returns

Branch Table

Data Accesses

Simple Data Accesses

Example of Using Memory Access Instruction

Data Type Conversion

Conversion of Data Size

Endian Conversion

Data Processing

64-Bit/128-Bit Add

64-Bit/128-Bit Sub

Integer Divide

Unsigned Integer Square Root

Bit and Bit Field Computations

Chapter 7 Memory System

Overview

Memory Map

Code Region (0x00000000e0x1FFFFFFF)

SRAM Region (0x20000000e0x3FFFFFFF)

Peripheral Region (0x40000000e0x5FFFFFFF)

RAM Region (0x60000000e0x9FFFFFFF)

Device Region (0xA0000000e0xDFFFFFFF)

Internal Private Peripheral Bus (PPB) (0xE0000000e0xE00FFFFF)

Reserved Memory Space (0xE0100000e0xFFFFFFFF)

Program Memory, Boot Loader, and Memory Remapping

Data Memory

Little Endian and Big Endian Support

Data Type

Effect of Hardware Behavior to Programming

Data Alignment

Access to Invalid Addresses

Use of Multiple Load and Store Instructions

Memory Attributes

Chapter 8 Exceptions and Interrupts

What Are Exceptions and Interrupts?

Exception Types on the Cortex-M0 Processor

Nonmaskable Interrupt (NMI)

Hard Fault

SVCall (SuperVisor Call)

PendSV (Pendable Service Call)

SysTick

Interrupts

Exception Priority Definition

Vector Table

Exception Sequence Overview

Acceptance of Exception Request

Stacking and Unstacking

Exception Return Instruction

Tail Chaining

Late Arrival

EXC_RETURN

Details of Exception Entry Sequence

Stacking

Vector Fetch and Update PC

Registers Update

Details of Exception Exit Sequence

Unstacking of Registers

Fetch and Execute from Return Address

Chapter 9 Interrupt Control and System Control

Overview of the NVIC and System Control Block Features

Interrupt Enable and Clear Enable

Interrupt Pending and Clear Pending

Interrupt Priority Level

Generic Assembly Code for Interrupt Control

Enable and Disable Interrupts

Set and Clear Interrupt Pending Status

Setting up Interrupt Priority Level

Exception Masking Register (PRIMASK)

Interrupt Inputs and Pending Behavior

Simple Interrupt Process

Interrupt Latency

Control Registers for System Exceptions

System Control Registers

CPU ID Base Register

Application Interrupt and Reset Control Register

Configuration and Control Register

Chapter 10 Operating System Support Features

Overview of the OS Support Features

Why Use an Embedded OS?

The SysTick Timer

SysTick Registers

Setting up SysTick

Using SysTick Timer for Timing Measurement

Process Stack and Process Stack Pointer

SVC

PendSV

Chapter 11 Low-Power Features

Low-Power Embedded System Overview

Low-Power Advantages of the Cortex-M0 Processor

Overview of the Low-Power Features

Sleep Modes

Wait-for-Event (WFE) and Wait-for-Interrupt (WFI)

Wait for Event (WFE)

Wait for Interrupt (WFI)

Wakeup Conditions

Sleep-on-Exit Feature

Wakeup Interrupt Controller

Chapter 12 Fault Handling

Fault Exception Overview

What Can Cause a Fault?

Analyze a Fault

Accidental Switching to ARM State

Error Handling in Real Applications

Lockup

Causes of Lockup

What Happens during a Lockup?

Preventing Lockup

Chapter 13 Debug Features

Software Development and Debug Features

Debug Features Overview

Debug Interface

Halt Mode and Debug Events

Debug System

Chapter 14 Getting Started with Keil MDK

Introduction to Keil MDK

First Step of Using Keil MDK

Create the Blinky Project

Create the Project Code

Project Settings

Compile and Build the Program

Using the Debugger

Other Project Configurations

Target, Source Groups

Compiler and Code-Generation Options

Simulator

Execution in RAM

Customizing the Startup Code in Keil

Using the Scatter Loading Feature in Keil

Chapter 15 Simple Application Programming

Using CMSIS

Using the SysTick Timer as a Single Shot Timer

UART Examples

Simple Input/Output

Retargeting

Developing Your Own Input and Output Functions

Simple Interrupt Programming

General Overview of Interrupt Programming

Dial Control Interface Example

Interrupt Control Functions

Different Versions of CMSIS

Chapter 16 Assembly Projects and Mixed-Assembly and C Projects

Project Development in Assembly

Recommended Practice in Assembly Programming

Structure of an Assembly Function

Simple Assembly Project Example

Allocating Data Space for Variables

UART Example in Assembly

Additional Text Output Functions

Complex Branch Handling

Mixed-Language Projects

Calling a C Function from Assembly

Calling an Assembly Function from C Code

Embedded Assembly

Accessing Special Instructions

Idiom Recognitions

Chapter 17 Using Low-Power Features in Programming

Overview

Review of Sleep Modes in the Cortex-M0 Processor

Using WFE and WFI in Programming

Using the Send-Event-on-Pend Feature

Using the Sleep-on-Exit Feature

Wakeup Interrupt Controller (WIC) Feature

Event Communication Interface

Developing Low-Power Applications

Example of Using Low-Power Features on the LPC111x

Chapter 18 Using SVC, PendSV, and Keil RTX Kernel

Introduction

Using the SVC Exception

Using the PendSV Exception

Using an Embedded OS

Keil RTX Real-Time Kernel

Features Overview

OS Startup Sequence

Simple OS Example

Intertask Communications

Event Communications

Mutual Exclusive

Semaphore

Mailbox Messages

Periodic Time interval

Other RTX Features

Application Example

Chapter 19 Getting Started with the ARM RealView Development Suite

Overview

Simple Application Example

Using the Scatter Loading File

Example with Vector Table in C

Using MicroLIB in RVDS

Using Assembly for Application Development in RVDS

Flash Programming

Debugging Using RealView Debugger

Using Serial Wire Debug with the RealView Debugger

Retargeting in RVDS

Chapter 20 Getting Started with the GNU C Compiler

Overview

Typical Development Flow

Simple C Application Development

CodeSourcery Common Startup Code Sequence (CS3)

Using a User-Defined Vector Table

Using Printf in gcc

Inline Assembler

SVC Example in gcc

Hard Fault Handler Example

Flash Programming and Debug

Chapter 21 Software Porting

Overview

ARM Processors

Differences between the ARM7TDMI and the Cortex-M0

Operation Mode

Registers

Instruction Set

Interrupts

Porting Software from the ARM7TDMI to the Cortex-M0

Startup Code and Vector Table

Interrupt

C Program Code

Assembly Code

Atomic Access

Optimizations

Differences between the Cortex-M1 and the Cortex-M0

Instruction Set

NVIC

System-Level Features

Porting Software between the Cortex-M0 and the Cortex-M1

Differences between the Cortex-M3 and the Cortex-M0

Programmer’s Model

NVIC and Exceptions

Instruction Set

System-Level Features

Debug Features

Porting Software between the Cortex-M0 and the Cortex-M3

Porting Software between the Cortex-M0 and the Cortex-M4 Processor

Porting Software from 8-Bit/16-Bit Microcontrollers to the Cortex-M0

Common Modifications

Memory Requirements

Nonapplicable Optimizations for 8-Bit or 16-Bit Microcontrollers

Example: Migrate from the 8051 to the ARM Cortex-M0

Chapter 22 Cortex-M0 Products

Overview

Microcontroller Products and Application-Specific Standard Products (ASSPs)

NXP Cortex-M0 Microcontrollers

NuMicro™ Microcontroller Family

Mocha-1 ARM Cortex-M0 Configurable Array

Melfas MCS™-7000 Series Touch Screen Controllers

Compilers and Software Development Suites

Keil Microcontroller Development Kit (MDK)

TASKING VX-Toolset for ARM

IAR Embedded Workbench for ARM

CrossWorks for ARM

Red Suite

LabView C Code Generator

Development Boards

LPCXpresso

IAR KickStart Kit for LPC1114

LPC1114 Cortex-M0 Stamp Module

Keil Cortex-M0 Boards

Appendix A: Instruction Set Summary

Appendix B: Cortex-M0 Exception Type Quick Reference

Appendix C: CMSIS Quick Reference

Appendix D: NVIC, SCB, and SysTick Registers Quick Reference

Appendix E: Debug Registers Quick Reference

Appendix F: Debug Connector Arrangement

Appendix G: Linker Script for CodeSourcery G++ Lite

Appendix H: Example Code Files

Appendix I: Troubleshooting

Index