The Definitive Guide to ARM® Cortex®-M0 and Cortex-M0+ Processors, Second Edition

742 Pages·2015·61.42 MB·English

by  Joseph Yiu

The Definitive Guide to
® ®
ARM Cortex -M0 and
Cortex-M0+ Processors
Second Edition
Joseph Yiu
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This book is dedicated to the memory of my sister, Lucia Yiu
.
Adventurous, supportive, loads of fun and full of energy
the whole family miss you.
Foreword
I started my professional career in 1982, working in a microprocessor software department,
and focused for years on the 8051 as this microcontroller architecture wasdduring the
1990sdthe engine for all types of embedded applications. Over decades, I was part of a
booming embedded industry that created a wide spectrum of processor architectures. During
this time, the microcontroller market became extremely fragmented with numerous silicon
vendors and technologies. Some years ago, every embedded application was created from
scratch with no software reuse and ground-up training for engineers to cope with the project
challenges.
But over the years, microcontroller systems became increasingly complex and demanded even
higher performance to fulfil thewishes for more features and convenient operations. Often
these systems are also price sensitive and therefore increasingly microcontroller systems are
designed as single-chip designs based on high performance 32-bit processors, which are
dominant today. Meanwhile, cost pressure and challenging software development require
standardization, while, at the same time, a diverse I/O connectivity requires a range of devices.
(cid:1) (cid:1)
To solve these challenges, the embedded industry has established the ARM Cortex -M
processor series as the de-facto standard microcontroller architecture. These processors are
licensed to more than 200 companies that produce devices ranging from standard
microcontrollers to domain-specific sensors to complete radio communication systems for
the Internet of Things.
To support a wide range of applications ARM launched multiple processors that implement
the Cortex-M architecture. At the low-end of the spectrum, the Cortex-M0 and Cortex-M0+
is available for applications that were previously dominated by 8-bit microcontrollers. It is
no surprise that these processors are today widely used for low-cost devices.
With the availability of even more capable microcontrollers, software development for these
devices has become increasingly complex. Use of real-time operating systems is rapidly
becoming an industry best practice and the use of prebuilt middleware as well as software
reuse is gaining importance for productive software engineering. Combining software
building blocks often poses a problem for developers, but industry standards are a great way
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Foreword
to reduce system development costs and speed up time-to-market. And the Cortex-M
processor architecture along with the CMSIS software programming standard is the basis
for this hardware and software standardization.
Joseph’s book, The Definitive Guide to ARM(cid:1) Cortex(cid:1)-M0 and Cortex-M0+ Processors,
gives you the foundation for designing and creating applications for all devices that are
based on ARM Cortex-M0 or Cortex-M0+ processors. I recommend this reading for
practical every embedded engineer as it gives you in-depth ground-up knowledge for your
day-to-day work.
Reinhard Keil
Director of MCU Tools, ARM
xxii
Preface
Embedded system technologies have changed a lot since 2011, when the first edition of this
book was published. In 2012, ARM(cid:1) announced the Cortex(cid:1)-M0þ processor and, in 2014,
the Cortex-M7 processor was announced. Today, the Cortex-M processor is used in many
microcontrollers, as well as in a range of mixed signals and wireless communication chips.
In addition to processor design, embedded software development technologies have also
moved on. As the use of the ARM Cortex-M microcontrollers has become more common,
this has enabled microcontroller software developers to write more sophisticated
applications. At the same time, the quest for better battery life and energy efficiency
continues, along with improvements in development suites.
Withallthesechanges,microcontrollerusersneedtoadapttonewtechnologiesquicklyand
thustheavailabilityoftechnicalliteratureisbecomingmoreandmoreimportant.This
neweditionisthereforefullofnewinformationandenhancement.Inadditiontothenew
informationrelatedtotheCortex-M0þprocessor,examplesofusingseveralpopular
developmentsuitesarealsocovered.Forexample,thebookhasdetailedexamplesofutilizing
low-powerfeaturesinmicrocontrollersandillustrationsofusingRTOSinasimpleapplication.
As the Internet of Things (IoT) is getting more attention and becoming more main-stream,
there are more people taking an interest in and starting to learn about embedded
programming. There are also more universities and colleges that are now moving on from
teaching about legacy 8-bit and 16-bit microcontrollers to starting to teach students about
32-bit embedded processors- like ARM Cortex-M processors. Therefore, many parts of this
book have been rewritten and many basic examples have been included to make this even
more suitable for beginners, students, hobbyists, etc.
There are of course audiences who demand in-depth information such as professional
embedded software developers, researchers, or even semiconductor product designers. To
cater for their needs, this book also covers a wide range of technical details and advanced
examples.
I hope that you will find this book helpful and enjoy using Cortex-M processors in your
next embedded projects.
xxiii
Acknowledgment
Many people have assisted me during the time I have been writing this book and this
includes the assistance given when I wrote the first edition.
First of all, many thanks to the various readers who have provided feedback for the first
edition, enabling me to improve the contents of this second edition.
There are also a number of people in ARM, including Colin Jones and Edmund Player for
reviewing the contents. A number of companies have also provided me with a deal of
assistance, including ST Microelectronics, Freescale and IAR Systems.
Of course, without the successful first edition, the second edition would not be here.
I would therefore like to express my gratitude to the following people for their help in the
first edition: Amit Bhojraj, Bob (Robert) Boys, David Donley, Derek Morris, Dominic
Pajak, Drew Barbier, Jamie Brettle, Jeffrey S. Mueller, Jim Kemerling, Joe Yu, John Davies,
Jon Marsh, Kenneth Dwyer, Milorad Cvjetkovic, Nick Sampays, Reinhard Keil, Simon
Craske, William Farlow.
I would also like to thank the staff from Elsevier for their professional work in getting this
book published.
And finally, a big thank you to all of my friends for their encouragement and for forgiving
me for being slightly anti-social (I hear you ☺), while I was working on this book.
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Terms and Abbreviations
Abbreviations Definitions
AAPCS ARMarchitectureprocedurecallstandard
AHB Advancedhigh-performancebus
ALU Arithmeticlogicunit
AMBA Advancedmicrocontrollerbusarchitecture
APB Advancedperipheralbus
API Applicationprogramminginterface
ARMARM ARMArchitectureReferenceManual
BE8 Byteinvariantbigendianmode
BPU Breakpointunit
CMSIS Cortexmicrocontrollersoftwareinterfacestandard
CMOS Complementarymetaloxidesemiconductor
CPU Centralprocessingunit
DAP Debugaccessport
DDR Doubledatarate(memory)
DS-5 DevelopmentStudio5
DWT Datawatchpointandtraceunit(unit)
EABI/ABI Embeddedapplicationbinaryinterface
EWARM IARembeddedworkbenchforARM
EXC_RETURN Exceptionreturn
FPGA Fieldprogrammablegatearray
GPIO Generalpurposeinput/output
GPU Graphicprocessingunit
gcc GNUCcompiler
HAL Hardwareabstractionlayer
ICE In-circuitemulator
IDE Integrateddevelopmentenvironment
ISA Instructionsetarchitecture
ISR Interruptserviceroutine
JTAG Jointtestactiongroup(astandardoftestanddebuginterface)
LR Linkregister
LSB Leastsignificantbit
MCU Microcontrollerunit
MDK/MDK-ARM ARM(cid:1)Keil(cid:3) MicrocontrollerDevelopmentKit
MSB Mostsignificantbit
Continued
xxvii
Terms and Abbreviations
dcont’d
Abbreviations Definitions
MTB Microtracebuffer
MSP Mainstackpointer
NMI Non-maskableinterrupt
NVIC Nestedvectoredinterruptcontroller
OS Operatingsystem
PC Programcounter
PCB Printedcircuitboard
PSP Processstackpointer
PSR/xPSR Programstatusregister
RTC Real-timeclock
RVDS ARMRealViewDevelopmentSuite
RTOS Real-timeoperatingsystem
RTX KeilReal-TimeeXecutivekernel
SCS Systemcontrolspace
SCB Systemcontrolblock
SoC System-on-a-Chip
SP Stackpointer
SPI Serialperipheralinterface
SWD Serialwiredebug
TAP Testaccessport
TRM TechnicalReferenceManual
UART Universalasynchronousreceivertransmitter
ULP Ultralowpower
USB Universalserialbus
WIC Wakeupinterruptcontroller
xxviii
Conventions
Various typographical conventions have been used in this book, as follows:
(cid:129) Normal assembly program codes:
MOVR0,R1;MovedatafromRegisterR1toRegisterR0
(cid:129) Assembly code in generalized syntax; items inside “< >” must be replaced by real
register names:
MRS<reg>,<special_reg>;
(cid:129) C program codes:
for(i=0;i<3;i++){func1();}
(cid:129) Pseudo code:
if(a>b){.
Values:
1. 4’hC, 0x123 are both hexadecimal values
2. #3 indicates item number 3 (e.g., IRQ #3 means IRQ number 3)
3. #immed_12 refers to 12-bit immediate data
4. Register bitsdTypically used to illustrate a part of a value based on bit position.
For example, bit[15:12] means bit number 15 down to 12.
Register access types:
1. R is Read only
2. Wis Write only
3. R/Wis Read or Write accessible
4. R/Wc is Readable and cleared by a Write access
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