1. Embedded System Software and Hardware Basics
Embedded Systems Software Training Center
Embedded System Software and Hardware Basics
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2. Assumptions for Using this Teaching Material
NEXCESS Beginner's Course
Fundamentals of Embedded Software Development Technology
Embedded System Software Basics
Copyright (C) 2006 by Nagoya University Extension Courses for Embedded Software Specialists
Copyright (C) 2006 by Hiroaki Takada and Masaki Yamamoto
The author (s) named above allow this content (including any adaptation or translation thereof) to be used, duplicated, modified, translated and/or redistributed for free only if such usage clears the requirements given in (1) to (3) below.
The copyright notice found in this box shall be duplicated in the content in its original form.
(2) When this content is adapted or translated, a mention of such adaptation or translation shall be included in the content. A copyright notice for such adapters or translators shall be given separately from the copyright notice found in this box.
(3) Users of this context shall indemnify the author(s) for any damages, direct or indirect, that may result from its use.
* Part of this content has been prepared as part of the Nagoya University Extension Courses for Embedded Software Specialists (NEXCESS), financed by a Ministry of Education, Culture, Sports, Science and Technology science and technology promotion coordination subsidy.
* Product names and service names appearing in this content are either trademarks or registered trademarks of their respective owners.
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3. Welcome Instructor Introduction Objectives and Content Class Materials
Agenda
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4. Instructor Introduction
Matveev Alexey Igorevich
Senior software developer,
DSR corp.
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5. All lectures themes Embedded System Software and Hardware Basics
Embedded Systems Peripherals
Programming for Embedded Systems and RTOS Basics
Itron Basics

6. Objectives Understand what are embedded systems
Understand the challenges and diversity of embedded systems
Understand embedded systems CPU operating principle
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7. Class Materials
Embedded Systems Software Basics diagrams and Hands-on Exercises are available on site in training materials section:
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8. Agenda What is an Embedded System?
Challenges and Diversity of Embedded Systems
Definitions of the Embedded Software
Embedded Hardware Basics
CPU operating principle
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9. Basic Knowledge of the Embedded System
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10. What is an Embedded System?
There is some ambiguity in the use of the word embedded with variation of use from person to person.
The embedded system in general terms:
An embedded system is a system that has embedded software and computer hardware, which makes it a system dedicated for an application(s) or specific part of an application or a product or part of a larger system
In a broad sense, the term "embedded system“ applies to all systems except generic purpose computers such as PCs.
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11. Where Embedded Systems are Used
The number of microprocessors used in embedded systems is nearly 98% of all produced microprocessors. 2% are used by general purpose PCs, big IT systems, and servers.
The end user usually perceives embedded software as a set of functions that the system provides.
Devices which are embedded systems:
Electrical household devices (microwaves, rice cookers, drying machine, washing machines, air-conditioners).
Audio-visual equipment (TVs, videos, digital cameras, audio equipment).
Personal information equipment (PDAs, electronic organizers, car navigation systems).
PC peripheral equipment (printers, scanners, DVD-drives).
Networking equipment (switching equipment, network routers, hubs).
Medical apparatus (blood pressure meters, electrocardiographs, X-rays, CT scanners).
Space/military (rockets, satellites, missiles, rovers).
Scientific and measurement tools (oscilloscopes, IC testers, electric power meters, DDMs).
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12. Challenges of Embedded Systems
Real time
The embedded system's timing must provide the expected action within a maximum specified time under all circumstances.
For example: engine control system
Reliability
Unexpected behavior from an embedded system might seriously damage its environment. Embedded software must operate for decades without service.
For example: sensors in home automation systems
Safety
Embedded software has an impact on people and can potentially pose a safety hazard. Safety is crucially important especially in systems such as airplanes, cars, or industrial plants.
For example: steering and brake equipment in a car
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13. Challenges of Embedded Systems (cont.)
Security
Secured I/O to avoid data loss or damage.
For example: automatic cash terminal, payment equipment, vending machines
Limited Resources
Small memory space and limited data-processing capabilities, low-cost microcontrollers, and low power consumption.
For example: ZigBee devices with different profiles
Heterogeneity
During long lifetime environment changes: sensors and hardware parts.
For example: BT radio chip us used in different devices
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14. Main Characteristics of the Embedded System
An embedded system is a dedicated system
Strict hardware restrictions
High reliability
Real time operations
Embedded System = Embedded Software + Embedded Hardware
Hardware: Flesh and blood of an Embedded System. CPU (MPU, MCU) is the heart of an Embedded System.
Software: The spirit of an Embedded System.
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15. Basic Knowledge of the embedded software
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16. Definitions of Embedded Software
The traditional definition:
Software that is used in embedded systems.
Narrow sense definition:
Software that is considered as a part of a product, specific to the equipment.
！Java programs downloaded onto mobile phones is not embedded software.
！The BIOS of PCs is embedded software.
！Software flashed into LSI (Large Scale Integration) for control is an embedded software.
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17. Software Embedded in Equipment and in LSI
DSP – Digital Signal Processor
LSI – Large Scale Integration
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18. Challenges of Embedded Software Development
Programming closely related to hardware
Reason: differences in the structure of the hardware and peripheral devices for individual systems.
The quality of program depends on the programmer’s capabilities. It makes development difficult.
For example: different radio modules for ZB and BT, different transport layer and commands.
Low Resources for Software
Limitation of CPU, RAM, and ROM.
Need to do a lot of optimization for code size and memory usage.
Example: ZigBee stack, code size 128 Kb, memory 64 Kb.
Separation of the development and the target environment
Development on targeted systems is not always possible. An environment for cross development and a remote debug is required.
There are systems which need to be verified and debugged without being stopped.
For example: development for ARM, MIPS, JTAG can be used but only for simple tasks, main debug is done using logging.
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19. Challenges of Embedded Software Development (cont.)
Possibility of parallel development and co-design with hardware
Need to get complete product as quickly as possible.
System verification and debugging when both hardware and software are unreliable.
The need for experienced experts.
For example: For ZB development, a similar processor was used instead of a target platform.
Various platforms (hardware, OS)
The hardware and OS are optimized for each system.
For example: ZB is developed for ARM and 8051.
High costs of verification and testing
The demand for high reliability.
Indeterminacy due to timing.
Example: RDBMS in Sony multimedia center.
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20. Challenges of Embedded Software Development (cont.)
Exception processing software
Very high percentage of exception and diagnostic processing on system failure.
Exception processing could be a problem in terms of time constraints.
For example: BT, working with radio module – handle packet loss and incorrect incoming data.
Components Interaction
Components interact with each other, need to handle them correctly.
For example: distance measurement using radio signals, multiple devices interaction, and external environment influence.
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21. Breakdown of the Total Development Cost in the Operating Department
The cost of software development accounts for 40% of total development costs.
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22. Types of Targeted Processors
The 32 bits era
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23. Programming Languages
C is most popular, works well with H/W
C allows writing programs with simple flat structure
Assembler is used for DSP development and optimization
C++ is less popular because of overhead caused by programming methods
C++ cross compiler is not available on some platforms
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24. Embedded hardware basics
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25. Hardware in Embedded Software Development
Embedded software development requires knowledge of hardware
because programming is close to hardware
Embedded software is intended to control the system
Programming deals with working directly with hardware
C programming concepts are used
Pointers, ROM/RAM, device registers
Polling, interrupts
Embedded software specific
General-purpose computer technology is used
Low power consumption, debugging, reliability, etc.
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26. Embedded Hardware Basics
A computer does mainly four functions:
Receive input: Through various input devices
Process information: Perform arithmetic or logical operations on the information
Produce output: through output devices
Store information: storage device
Computer hardware falls into three categories:
Processing hardware: CPU
Peripheral devices: handle interaction between user/another computer and CPU
Memory: stores information
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27. Embedded Hardware Basics
Processor (CPU) is connected by a bus with I/O interfaces and memory
LSI (large-scale integration) is used in each separate element
Single-chip microcontroller
Peripheral device
CPU
Memory
I/O
Interface
Auxiliary
circuit
Bus
I/O interface
(LAN controller)
Memory
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28. Processor Basics ALU (Arithmetic Logic Unit)
Digital circuit that performs integer arithmetic and logical operations.
CPU (Central Processing Unit)
Performs data transfers, ALU, stack and input/output operations.
MPU (Microprocessor Unit)
Includes CPU and additional (FPU, caches, pipeline, etc.) blocks in single VLSI chip.
MCU (Microcontroller Unit)
Includes CPU, memory and several hardware units – peripheral (GPIO, timers, interrupt controller, etc.) in single VLSI chip.
SoC (System on chip)
Contains MCU, digital, analog and often radio-frequency units.
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29. Processor Basics(cont.)
Memory
Peripherals
Control Unit RF
ALU
transceiver
Registers
Bus
CPU
MCU
SoC

30. Embedded Processors Diversity
Wide spectrum of embedded hardware: from 8- to 64-bit processors
Electronic thermometer:
ATMEL AVR ATtiny15 (8 bit, 1.6MHz, 1kB ROM, No RAM)
Wrist watch:
Texas Instruments MSP430F5212 (16 bit, 25 MHz, 128kB ROM, 8kB RAM)
Smart Home control panel:
ARM Cortex-M3 STM32F207VGT6 (32 bit, 120 MHz, 1MB ROM, 128kB RAM)
Wi-Fi routers, printers:
WRTnode MIPS24KEc (32 bit, 600 MHz, 32M ROM, 128M RAM)
Car navigation systems:
ARM Cortex-A7 Allwinner A20 (32 bit, 1GHz, 4GB ROM, 512MB RAM)
ATMs, POS terminals:
even x86-64 processors (64 bit, 2.2 GHz, 120GB ROM, 2GB RAM )
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31. RISC and CISC
Processor architecture classification by the type of instruction set
CISC
Complex Instruction Set Computer
Variable length and complex instructions
Example: PDP-11, VAX, x86
RISC
Reduced Instruction Set Computer
Easy to increase frequency
Fixed-length instruction set, one instruction per clock
Load-store architecture, all modifications are done in registers
Simplified MMU (memory management unit), interrupt and exception handling
Example: ARM, Atmel AVR, MIPS, DEC Alpha
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32. Reading instruction fetch data
Registers
Register is fast memory available as part of a CPU
Registers are used to store data and processor state
Program data is stored in memory
The processor can not directly operate with values stored in memory
Put the value in the register, perform calculations, write back to memory
c = a + b;
Compiling results
Address
Register
load r1, 0x10
0x01
Reading instruction fetch data
load r2, 0x11
CPU
ROM (program)
add r1, r2
store r1, 0x12 r1 5
a(3)
0x10 r2 2
b(2)
0x11
RAM (data)
c(5)
0x12
Data write
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33. The Cortex-M3/M4 registers
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34. Type of Registers Link register Program Counter (PC)
General purpose registers (R0-R12)
R0-R12 are 32-bit general-purpose registers for data operations.
Registers r0-r7 are accessible by all instructions that specify a general-purpose register.
Registers r8-r12 are accessible by all 32-bit instructions that specify a general-purpose register.
Registers r8-r12 are not accessible by all 16-bit instructions.
Stack pointer
Register r13 is used as the Stack Pointer (SP).
Because the SP ignores writes to bits [1:0], it is autoaligned to a word, four-byte boundary.
Link register
Register r14 is the subroutine Link Register (LR).
Program Counter (PC)
Stores address of instruction to execute by the processor
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35. Type of Register (cont.)
Program Status Register
The Program Status Register (PSR) combines:
Application Program Status Register (APSR)
Interrupt Program Status Register (IPSR)
Execution Program Status Register (EPSR).
Exception mask registers
The exception mask registers disable the handling of exceptions by the processor. Disable exceptions where they might impact on timing critical tasks.
CONTROL register
The CONTROL register controls the stack used and the privilege level for software execution when the processor is in Thread mode and, if implemented, indicates whether the FPU state is active.
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36. Bus and Memory COPYRIGHT © 2016 DSR CORPORATION36

37. Serial Bus and Parallel Bus
A bus is a subsystem that transfers data between components inside a computer
Parallel Bus
Sends several data signals simultaneously over several parallel channels
SCSI, PCI, ISA, VMEBUS, AMBA…
Serial Bus
Sends data one bit at a time, sequentially, over a communication channel
PCI Express, IEEE1394, CAN, USB, Ethernet…
Parallel bus timing should be synchronized for all data channels that limits data rate for long distances. Therefore, for establishing connection between distant peers, serial bus is used.
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38. Processor Bus
Processor bus connects the processor with peripheral devices and memory, usually it is parallel bus
The main characteristics: transfer speed, combination of several bus types (peripheral and high-performance buses, for example)
Master
Sends read and write requests to the bus
Processor, DMA (Direct Memory Access), …
Slave
Receives read and write requests from the bus
Memory, I/O Interface (GPIO, UART), ...
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39. System Bus Address bus Is used to specify a physical address.
The width of the address bus determines the amount of memory a system can address
Can be wider than data bus (e.g., 16-bit address bus vs 8-bit data bus)
Data bus
Is used to transfer actual data
Consists of multiple bits of data
Example: If 16-bit, 2-byte
Control bus
Carries commands from the CPU and returns status signals from devices
Read/write request, wait command, external interrupt request
Bus width
Address range
Addressable size
8 bits
0x00-0xFF
256 bytes
16 bits
0x0000-0xFFFF
64 KB
32 bits
0x xFFFFFFFFF
4 GB
64 bits 
16 EB
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40. Bus Interaction Address bus Data bus Control bus Master Slave Slave
Master output, slave input
Data bus
Reads: master input, slave output
Write: master output, slave input
Control bus
Signal depends on situation
Master
Slave
Slave
CPU
Memory
I/O Interface
Control bus
Data bus
Address bus
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41. Bus Slave Selection Port enable (chip select)
Only one slave device is active and accepts requests from the bus
Decode address: get the most significant bits of the address
Memory Map
Port enable
0x0000
Memory 1
Master
Slave
Slave
0x4000
Memory 2
CPU
Memory 1
Memory 2
0x8000 EN EN
Address Decoder
“00” active
0x1000 :
0x2000 :
0x4000 :
0x5000 :
The upper 2 bits
Chip Select
“01” active
Address signal
16-bit
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42. Memory A system usually deals with several kinds of memory:
RAM： Volatile
DRAM (dynamic RAM)： Large and relatively fast, must be refreshed
SRAM (static RAM)： Refresh is not needed, fast access
ROM： Nonvolatile
Mask ROM, PROM (programmable), UV-EPROM (ultra-violet erasable), EEPROM
Flash Memory: Nonvolatile
Can be rewritten in blocks
There is a limited re-write number
The write speed
Bus State Controller
Timing is different for each memory access, controller changes the settings according to the memory specification
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43. Endian
Endian is byte ordering when storing large data in external memory
Big-endian
store the most significant byte first
Little-endian
store the least significant byte first
Big-endian, little-endian terms come from “Gulliver’s travel” book – conflict how to crack boiled eggs
Example: 8-bit memory address 0x bytes of data store 0x
Big-endian
Little-endian
0x12
0x34
0x56
0x78
0x1000
0x1001
0x1002
0x1003
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44. Endian (cont.) Endianness of the processor
Processors: big-endian or little-endian
Switchable endian (bi-endian): allows to switch endianness on OS initialization or using a jumper
Different endian often causes an error while porting application or implementing communication between devices
The value of c variable:
In the big-endian， c == 0x12
In the little-endian ， c == 0x78
int i = 0x ;
char c = *（（char *） &i）;
Big-endian
Little-endian i
0x1000
0x12 i
0x1000
0x78
0x1001
0x34
0x1001
0x56
0x1002
0x56
0x1002
0x34
0x1003
0x78
0x1003
0x12
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45. BASIC KNOWLEDGE OF CPU OPERATING

46. Processor Basics Program is placed in memory (ROM or RAM):
Program instructions are initially stored in ROM;
Program can be executed directly from ROM;
Some processors can execute program from RAM – need to copy the program from ROM to RAM before execution;
Every time the CPU executes an instruction, it takes a series of steps called the machine cycle:
Fetching: fetches the instruction from the memory
Decoding: decode the program
Executing: execute the command, CPU carries out the instruction in order by converting them into microcode
Storing: store the results into registers
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47. Processor Booting Modern PCs:
User switches the system
CPU (x86) executed the code stored in ROM (BIOS) at 0xFFFF0 address
BIOS checks hardware and search for boot device
When boot device is found, execute OS from boot device.
OS starts and provides UI for interaction.
How does embedded system CPU know the address to execute the first instruction?
Answer: It uses Reset Exception address

48. Processor Booting (cont.)
Reset Exception
Each time when the system powers on or
soft reset is performed, it starts execution
from specific address called
“Reset Exception Vector”.
On startup:
PC = 0xFFFFC
PC = address(<Reset_handler>)
initialize user (USP) and
interrupt stack pointers (ISP)
execute main program
0xFFFFF
jmp <Reset_handler>
0xFFFFC
jmp <NMI_handler>
0xFFFF8
jmp <DBC_handler>
0xFFFF4 …
<Reset_handler>
mov.w USP,0x1000
mov.w ISP,0x2000
jmp main
nop … 48

49. Program Execution
This program runs successfully on PC but fails on MCU.
What’s wrong? Answer: Undefined behavior.
main.c
int main() {
uint8_t a = 1;
uint8_t b = 2;
uint8_t c;
c = a + b;
return 0; }
main.asm
...
load r1, 0x1000
load r2, 0x1001
add r1, r2
store r1, 0x1002
mov r1, 0
ret
There is no return from the main() function in embedded systems!

50. Program Execution (cont.)
This program runs successfully on MCU (but freezes on PC).
main.c
int main() {
uint8_t a = 1;
uint8_t b = 2;
uint8_t c;
c = a + b;
while(1) {}
return 0; }
main.asm
...
load r1, 0x1000
load r2, 0x1001
add r1, r2
store r1, 0x1002
jmp label1
label1:
Super-loop architecture:
MCU should continuously calculate something to be alive

51. Homework
Some application is implemented to run on a Windows 32 platform. You get a request to port it on some mobile device. What characteristics should you know about the mobile device platform? What parts of the initial application will be changed/added/removed? What challenges could you meet during porting?
You get a request to develop software for some part of the embedded system that could be ported later to another device. What should you take into account while developing the software? What subsystem, in general, will be in your application?
Tabulate the advantages and disadvantages of using programming languages as follows:
Machine coding
Assembly coding C
C++
Java
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52. Homework
Make data and functions prototype in C for interface that handles packet received from remote side. Packet is received in little-endian. Interface maybe compiled to run on big-endian or little-endian CPU. Prototype shows what data structure is used to store received data and how it is filled
Packet structure:
Packet header
Configuration Bit Mask
Length: 4 bytes
stack_profile:4
protocol_version:4
Packet type: 2 bytes
reserved:2
Configuration: 2 bytes, bitmask
capacity:1
Value A: 1 byte
device_depth:4
Value A: 1 byte
end_device_capacity:1
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53. Authors Basic knowledge of the embedded system
Hiroaki Takada (Nagoya University)
Basic knowledge of the embedded software
Masaki Yamamoto (Nagoya University)
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54. References Embedded systems:
Raj Kamal, “Embedded Systems: Architecture, Programming and Design – 2ed”
Christof Ebert, Jurgen Salecker, “Embedded Software-Technologies and Trends”
Steve Heath, “Embedded Systems Design - 2ed”
Michael Barr; Anthony J. Massa, “Programming embedded systems: with C and GNU development tools”
System and local bus.
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