Introduction to Embedded Systems
Contents
1. the current US Air Force front line jet fighter contains about 1 7 million LOC e The F 35 Joint Strike Fighter will contain about 5 7 million lines of code Boeing s 787 Dreamliner contains about 6 5 million lines of code e A high end BMW or Mercedes will have around 100 million LOC e The radio and navigation software in the S Class Mercedes requires over 20 million LOC and the car contains as many embedded microprocessors as the new Airbus A380 excluding the plane s inflight entertainment system e Software and ES hardware can reach 35 to 40 per cent of a new car with software development contributing about 13 to 15 per cent of the cost 2 3 ES Characteristics Ref http www jopdesign com teaching EmbeddedIntro pdf Schoeberl M 2006 ES s are dedicated to a specific task Ref BERGER pp 8 9 NOER p 5 VAHID p 1 1 Embedded microprocessors are dedicated microprocessors They are programmed to perform one and only one task The microprocessor that controls a pacemaker does not should not and never will function as a word processor Is a smart phone an ES Personally I do not consider smart phones to be ES s because they are essentially a general purpose computer They can be programmed to perform different tasks and the software is easily changeable ES s are cost sensitive BERGER pp 8 10 In many devices the cost of the microprocessor related hardware and software is the bulk of the cost of the system i2. to connect the various circuits and components SoC s can be implemented using full custom VLSI ASIC s and FPGA s and are primarily designed using reusable intellectual property IP blocks from various vendors e g an ARM microprocessor a PowerVR GPU etc The chip designer selects blocks that will permit the system to function as intended while meeting various design constraints including cost power consumption area and interoperability i e does this IP block play well with the other IP blocks in the system 59 http en wikipedia org wiki Ada_ programming language 60 VHSIC Hardware Description Language http en wikipedia org wiki VHDL 61 http en wikipedia org wiki Forth programming language 62 http en wikipedia org wiki System_on_chip 63 http en wikipedia org wiki System_in package 64 http www computerhistory org semiconductor timeline 1974 digital watch is first system on chip integrated circuit 52 html 65 am old enough to remember how cool it was to get a digital watch for Christmas in 1976 also distinctly remember getting my first 4 operation calculator around that same time calculators began to be affordable around 1973 1974 wish had kept those things Incidentally Intel purchased Microma and very quickly got out of the digital watch business as prices began to plummet c Kevin R Burger Computer Science amp Engineering Arizona State Universit
3. 25 http courses cs vt edu cs3604 lib Therac_25 Therac_1 html The Therac 25 was a radiation therapy machine which was involved in six accidents between 1985 and 1987 in which pa tients were mistakenly given massive overdoses of radiation The root cause was a certain sequence of keystrokes entered within an 8 second interval If I remember correctly a couple of patients died from their injuries and some of the others were horribly burned leading to loss of function of the affected area Ariane 5 Flight 501 http _5 Flight 501 Ariane 5 was may still be a French rocket designed to carry satellites into space On 4 June 1996 flight 501 was launched and 37 seconds thereafter it began to veer off course heading somewhere near downtown Paris and self destructed The root cause was a data conversion from a 64 bit floating point value to a 16 bit signed integer value which overflowed The destroyed rocket and its payload was valued at 500 million Lesson A 64 bit IEEE 754 floating point value can range from approximately 10 A signed two s complement 16 bit integer can represent values in the range 32768 to 32767 If my math is correct 10 is a bit larger than 32767 In a mis sion critical application you would be a fool to not check for overflow when performing such a conversion Soviet Phobos 1 Mars Probe http en wikipedia org wiki Phobos _ program Phobos was a Soviet led program which launched two probes Phobo
4. SPI Ref KL46 SRM SPI module Ch 37 A serial I O protocol originally developed by Motorola but now widely implemented by other chip vendors and widely used in ES s We will discuss this module Ethernet A standard computer networking protocol designed for local area networks LAN s Ethernet is complicated as heck and the MKL46Z MCU does not have an ethernet module so we will not discuss it Universal Serial Bus USB Ref KL46 SRM USBOTG module Ch 35 A standard serial I O protocol widely used in the PC and electronics industries USB is also complicated as heck so we will not discuss it Controller Area Network CAN An asynchronous bus protocol that is widely used in the automotive and industrial control markets The MKL46Z module does not have a CAN controller so we will not discuss it 45 Lower case b means bits upper case B means bytes Consequently 100 Kbps is 100 x 2 bits per second and 100 KBps is 100 x 2 bytes per second which is 100 x 2 x 2 bits per second 46 http en wikipedia org wiki General_Purpose_Input Output 47 http en wikipedia org wiki Universal_asynchronous _receiver transmitter 48 http en wikipedia org wiki I C2 B2C 49 http en wikipedia org wiki Serial_Peripheral_Interface_Bus 50 http en wikipedia org wiki Ethernet 51 http en wikipedia org wiki Universal_Serial_Bus 52 http en wikipedia org wiki CAN _ bus c Ke
5. designed time constraint it will only temporarily degrade the quality of the system Example an audio or video decoder that misses an event which causes a temporary degradation in the quality of the audio or video signal Hard real time A hard real time event is one that the system must react to within the designed time constraints and if it does not it will lead to complete system failure In some hard real time systems this complete system failure may be catastrophic i e result in loss of property life or cause great damage to the environment Examples the air bag system in an automobile the system must respond to a collision event within 10 50 milliseconds a pacemaker missile defense system Many ES s either use no OS or if they do use a Real Time Operating System RTOS BERGER pp 9 10 Many ES s are relatively speaking simple enough that they do not require a full blown operating system In these cases a simple task scheduling executive may be sufficient The job of the executive is to run tasks at the required rates A Real Time Operating System RTOS provides many of the features of a traditional operating system including task scheduling resource sharing and interprocess communication In addition a RTOS is specifically designed to react to soft and hard real time events Windows and Linux for that matter are not RTOS s Windows is the antithesis of real time because I frequently see the stupid hourglass icon tell
6. going completely unrecognized by the device s user Creating a precise definition of such embedded systems is not an easy task An embedded system is nearly any computing system other than a desktop laptop or mainframe computer Ref WHITE p 1 Embedded systems are different things to different people To someone who has been working on servers an application developed for a phone is an embedded system To someone who has written code for tiny 8 bit microprocessors anything with an operating system isn t very embedded embedded systems are things like microwaves and automobiles that run software but aren t computers Ref BARR pp 1 2 An embedded system is a combination of hardware and software designed to perform a specific function Frequently an embedded system is a component within some larger system If an embedded system is designed well the existence of the processor and software could be completely unnoticed by a user of the device Combining these definitions we can come up with this definition An ES is characterized by e It is a microprocessor or microcontroller based computer system e It is programmed for a specific fixed function and that function cannot be changed by the end user e It has or consumes fewer resources e g memory processor power than a typical computer system e Many ES s must be highly reliable highly available and fail safe e g those in the medical or avionics field An emb
7. values and a D A converter or DAC performs the inverse operation We will discuss the MKL46Z ADC and DAC modules in CSE325 3 5 Software Obviously the processor in the ES executes instructions and therefore the system is controlled by software Overwhelm ingly the most popular ES programming language is Other reasonably popular languages are C C compilers have advanced to the point where they can generate very efficient code so it can be used in ES s although my hunch is that it would work better in 32 and 64 bit environments with a fair amount of memory and a RTOS Interestingly there is a dialect of C Embedded C or EC which is a reduced feature variant of C specifically designed for ES s although it does not seem to be very popular Assembly Language Ah my favorite programming language Assembly is the language of choice when you want complete control over the code e g when speed or space is of the utmost concern It s also popular in ES s with few resources such as small 4 or 8 bit microprocessor with only a few bytes of RAM Rarely would a nontrivial system today be written entirely in assembler although certain time critical parts may be Another use of assembler is to perform low level microprocessor operations that cannot be performed in a HLL e g in many processor architectures there are registers that are not accessible in C Java ME If people claim they are using Java in an ES then as far
8. CSE325 Embedded Microprocessor Systems Course Notes Part 1 Intro to Embedded Systems 1 Course Introduction See the syllabus at http www devlang com cse325 2 Introduction to Embedded Systems Ref Wikipedia Embedded System 2 1 What is an Embedded System Ref HEATH p 2 There are many definitions for this but the best way to define it is to describe it in terms of what it is not and with examples of how it is used An embedded system is a microprocessor based system that is built to control a function or range of functions and is not designed to be programmed by the end user in the same way that a PC is Yes a user can make choices concerning functionality but cannot change the functionality of the system by adding replacing software An embedded system is designed to perform one particular task Ref NOER p 5 An embedded system is an applied computer system as distinguished from other types of computer systems such as personal computers or supercomputers the definition is fluid and difficult to pin down Embedded systems are more limited in hardware and or software functionality than a PC An embedded system is designed to perform a dedicated function An embedded system is a computer system with higher quality and reliability requirements than other types of computer systems Ref VAHID p 1 1 they are embedded within larger electronic devices repeatedly carrying out a particular function often
9. It is in no way typical of an ES Some ES s are built around 4 or 8 bit microprocessors Some operate with as few as 16 to 256 bytes or RAM and in many cases 64 or 128 KB of RAM would be considered a significant amount of memory Processor speeds may be as low as 1 MHz Fancy screens and user interfaces are a rarity Cost and performance are major criteria for evaluating parts going into an ES with the goal of minimizing cost and maximizing performance but only to the point that the system will meet its requirements Sure you could put a 64 bit ARMv8 A chip running at 1 4 GHz with 512 KB of SRAM in a coffee maker and no doubt it would make a decent cup of coffee but it wouldn t be very cost effective when a 4 bit 0 5 MHz microcontroller with 32 bytes of SRAM and 1 KiB of ROM would do the same job and for a lot less in dollars Code stored in ROM BERGER pp 9 13 ES s typically do not contains hard drives CD or DVD drives or other forms of permanent storage other than some form of ROM flash is dominant today We will talk about memory and ROM later in the course but realize that when an ES is powered up the code must be present in ROM and ready to run Often the code or only part of it will be copied from ROM to RAM from where it will be executed but of course RAM is volatile so the code and data must be stored in a permanent form of memory when the system is powered down ES microprocessors have special debug circuitry BE
10. Memory vender bed package with a memory package on the top 66 67 68 69 c Kevin R Burger Computer Science amp Engineering Arizona State University Fall 2015 https en wikipedia org wiki Apple_ A8 https en wikipedia org wiki System _in _ package http am renesas com products package trend sip index jsp http en wikipedia org wiki Package on package CSE325 Embedded Microprocessor Systems Course Notes Part 1 Intro to Embedded Systems References ARM ARM ARM CALL ARM ISQR ARM M0 DUG ARM M0 TRM ARM V6M BARR BERGER FRDM KL46 PIN FRDM KL46Z QSG FRDM KL46 SCH FRDM KL46Z UM HEATH KL46 SDS KL46 SRM NOER OPENSDA VAHID WHITE ARM Architecture Reference Manual Rev I ARM 2005 Procedure Call Standard for the ARM Architecture Rev E 2 09 ARM 2012 ARM and Thumb 2 Instruction Set Quick Reference Card Rev M ARM 2008 Cortex M0 Device User s Guide ARM 2012 Cortexz M0 Technical Reference Manual Rev r0p1 ARM 2012 ARMv6 M Architecture Reference Manual Rev C 2010 Barr M Programming Embedded Systems in C and C O Reilly 1999 Berger A Embedded Systems Design CMP Books 2002 FRDM KL46Z Pinout FRDM KL46Z Quick Start Guide Rev 1 Freescale 2013 FRDM KL46Z Schematic Rev C Freescale 2013 FRDM KL46Z User s Manual Rev 1 0 Freescale Heath S Embedded Systems Desig
11. R Burger Computer Science amp Engineering Arizona State University Fall 2015 Page 2 CSE325 Embedded Microprocessor Systems Course Notes Part 1 Intro to Embedded Systems Therefore design B will lead to an additional profit of 40 320 000 40 315 000 5 000 5K may not seem like a lot but realize that for every penny we save in design B we earn an additional 5 000 over the lifetime of the product If de sign A uses a microprocessor which costs 3 53 and the engineers realize they can achieve the same product requirements by using a 1 17 microprocessor less powerful but powerful enough to meet the requirements in design B the overall savings would be 3 53 1 17 x 5000 1 180 000 and that would pay your salary for a year or two thus keeping you employed This example leads to an important point to understand when choosing a microprocessor for a design a design goal should always be to consider for adoption the least expensive microprocessor that will get the job done ES s often must meet real time constraints Ref BERGER pp 8 10 VAHID p 1 2 WHITE p 1 A real time system is one that must react to external events when they happen or as shortly thereafter as possible ES s are generally real time systems Real time events can be partitioned into two broad categories based on the consequences of missing a deadline Soft real time A soft real time event is one that if the ES does not react to it within the
12. RGER pp 9 15 Because of the limitations of ES processors most newer chips intended for ES s are manufactured with debugging circuitry built into the chip Motorola developed the first microprocessors with such circuitry in their 683xx processor family they called this Background Debug Mode BDM ARM chips employ the CoreSight debug and trace technology using either a JTAG or Serial Wire Debug SWD interface Require special development tools BERGER pp 9 14 WHITE pp 1 3 ES s can be more difficult to debug than a program for a PC because of the lack of hardware resources and real time requirements so there are various debugging tools and techniques that are commonly used As mentioned above modern microcontrollers for the ES market contain specialized dedicated debug hardware built into the processor The software debugger runs on a PC and communicates with the microcontroller usually over USB Freescale puts an OpenSDA debug interface on their Kinetis development boards including the FRDM KL46Z board we will use in this course OpenSDA consists of a Kinetis K20 MCU which interfaces the PC based software debugger to the target Kinetis MCU OpenSDA also provides the ability to program the flash of the target MCU Freescale provides a customized version of Eclipse called CodeWarrior which includes the C C IDE compiler assembler linker software libraries and other tools 14 The Renesas wPD67 68 69 family http do
13. and these can be very expensive to design and manufacture an ASIP less expensive to design and manufacture can be reprogrammed via software But unlike a general purpose processor which most likely implements many instructions that are unneeded an ASIP has a limited set of instructions a custom datapath that are applicable to implementing certain types of programs Probably the most common type of ASIP is a Digital Signal Processor DSP which a processor customized for digital signal processing applications think audio and video coding and decoding One very common digital signal processing application is in cell phones where an analog signal your voice must be quickly digitized converted into digital format and processed or coming the other direction the digital signal coming from the cell tower must be converted into analog format and sent to the speaker ASIP advantages include e Will achieve better performance power and size than a GP processor e More programmable flexibility than a SP processor Disadvantages e NRE and unit costs may be very high but not as high as a SP processor e Special software tools such as a custom compiler may need to be built if they are not available from other vendors e Ifa special compiler is not available one can always code a large part of the application in assembly language but this slows down software development 3 1 2 Processor Implementation Ref VAHID p 1 8 Every pro
14. as I am concerned it s not really an ES Sure Android apps are written in Java but since a smart phone ain t an ES that don t count C See Java ME I am clueless 53 http en wikipedia org wiki Programmable_Interrupt__Controller 54 http en wikipedia org wiki Analog to digital converter 55 http en wikipedia org wiki Digital to analog converter 56 http blog vdcresearch com embedded_sw 2010 09 what languages do you use to develop software html Although the data is 5 years old doubt the distribution has changed much ES programmer seem much less likely to jump on X is the next best language bandwagon the way web developers are because C is such a great language 57 http en wikipedia org wiki Embedded _C 2B 2B 58 http en wikipedia org wiki Java_Platform Micro Edition c Kevin R Burger Computer Science amp Engineering Arizona State University Fall 2015 Page 13 CSE325 Embedded Microprocessor Systems Course Notes Part 1 Intro to Embedded Systems Ada Ada is a statically typed imperative and OO programming language designed under contract to the US Department of Defense in the early 1980 s It was specifically designed for embedded and real time systems programming It is based on the Pascal programming language and if you ve studied any VHDL you will notice that VHDL syntax is similar in many respects to Ada In the mid 1980 s Ada was widely percei
15. c tor companies is called a pure play foundry The largest of these is the Taiwan Semiconductor Manufacturing Company TSMC c Kevin R Burger Computer Science amp Engineering Arizona State University Fall 2015 Page 9 CSE325 Embedded Microprocessor Systems Course Notes Part 1 Intro to Embedded Systems Disadvantages e Very high NRE cost design and long turnaround times weeks to months before the chip is manufactured e Only cost effective in very high volume applications e Post production bugs can be very expensive to fix Semi Custom Application Specific Integrated Circuit ASIC VAHID p 1 8 A standard cell ASIC is a design in which the lower layer the transistor layer is fully or mostly built and the engineer designs the middle logic gate and upper wiring layers In a gate array ASIC the transistor and gate layers are prebuilt and the engineer simply designs the wiring layer ASIC s are widely used in ES s to implement single purpose and ASIP designs as they still provide very good performance power and size with less NRE cost than a full custom design But they are still costly to design although gate array ASIC s are less costly than standard cell ASIC s have relatively long turnaround times and design mistakes can still be very costly to correct Programmable Logic Device PLD VAHID p 1 9 In a PLD all of the layers transistor logic gate wiring exist Programming consists of creating o
16. cessor must eventually be implemented in silicon as an integrated circuit IC or chip At an abstract view semiconductor chips consist of three layers on top a silicon substrate Wiring Logic Gates Transistors Silicon Full Custom VLSI Design VAHID p 1 8 In a full custom design Very Large Scale Integration or Ultra Large Scale Integration the engineer designs the chip from the bottom silicon layer up and then sends the design to an IC fab for fabrication e g Intel TI IBM Samsung and many other companies will do this for you This is exactly the way chip makers such as AMD and Intel design their microprocessor IC s Advantages e Will yield the best performance power consumption and size of any implementation 31 http en wikipedia org wiki Digital_signal__processor 32 http en wikipedia org wiki Integrated _ circuit 33 The future is in 3D integrated circuits which stack multiple layers wiring gates transistors on top of each other 34 VLSI circuits consist of 100 000 transistors The term ULSI is used by some to refer to IC s that integrate 1 000 000 transistors 35 http en wikipedia org wiki Fab semiconductors A company that manufacturers their own chips as well as fabricating chips for customers is known as a foundry A company owning a fab that does not design their own chips but rather operates the fab for implementing the designs of fabless semicondu
17. cumentation renesas com doc DocumentServer U14935EJ2V1DS00 pdf The venerable Intel 8 bit 8051 archi tecture https en wikipedia org wiki Intel_MCS 51 is still widely used 15 That s not a typo meant bytes For example the PIC1OF20x family http ww1 microchip com downloads en DeviceDoc 40001239E pdf which comes in two flavors with a whopping 16 or 24 bytes of SRAM 16 http en wikipedia org wiki Background Debug Mode _interface http www freescale com files microcontrollers doc app__note AN3335 pdf 17 http www arm com products system ip debug trace 18 http en wikipedia org wiki Joint_Test_Action Group http www corelis com education JTAG Tutorial htm 19 http www arm com products system ip debug trace coresight soc components serial wire debug php 20 http www freescale com webapp sps site prod__summary jsp code OPENSDA c Kevin R Burger Computer Science amp Engineering Arizona State University Fall 2015 Page 6 CSE325 Embedded Microprocessor Systems Course Notes Part 1 Intro to Embedded Systems ARM has developed the mbed suite of web based development tools for the ARM architecture mbed provides a free C C software library the mbed SDK the mbed Hardware Development Kit and the mbed C C IDE The platform is designed for rapid prototyping of produces based on ARM microcontrollers We will not be using mbed in CSE325 but you might
18. e ES market 3 3 1 Timers and Counters All computer systems must be able to count and keep track of time A typical microcontroller will contain several different types of timers and counters timers and counters are closely related as timers are implemented using counters Watchdog Computer Operating Properly COP Timer Ref KL46 SRM SIM module 3 4 10 A programmable countdown timer that must be kicked periodically to prevent the counter from reaching zero If the counter reaches zero the watchdog can be programmed to trigger a system reset In a correct program the watchdog timer will never expire so these are used to reset the system when a bug manifests itself and causes the system to lock up or go off the deep end We will probably not do anything with the COP in CSE325 other than to disable it at startup Programmable Interval Timer Ref KL46 SRM PIT module Ch 32 A programmable timer that is designed to generate interrupts at a desired rate We will study this timer module in CSE325 Input Capture Ref KL46 SRM TPM PWM module 31 4 4 A timer feature that can monitor an I O pin for a change in signal When the change occurs the timer will store the value of the timer counter in a register and if desired generate an interrupt We will use this module in CSE325 Output Compare Ref KL46 SRM TPM PWM module 31 4 5 A timer feature that can set or clear an I O pin when the timer counter reaches a pro
19. e The system will generally be of lower cost because one part replaces many The system may use a smaller PCB due to the reduced parts count e The system may be more reliable because fewer packages means fewer solder joints and fewer interconnects e A microcontroller may offer better performance than a microprocessor because all signals stay on the chip e A microcontroller design may radiate less RF energy fast signals on a PCB radiate RF energy Single Purpose Processor Ref VAHID p 1 6 A single purpose processor is one designed to execute exactly one program these types of processors are sometimes referred to a co processors because they are part of a system containing a microprocessor or microcontroller and the microcontroller offloads some of the work to the co processor or accelerators because they are employed to speed up a compute intensive task and or to offload the task from the microcontroller The basic difference between a single purpose and general purpose processor is that where a general purpose processor has an execution unit designed to execute a wide variety of instructions a single purpose processor will have an execution unit designed to execute a specific set of instructions making up a program think of it like a software program implemented in hardware An example would be an MP3 codec chip Advantages of designing a single purpose processor include e May achiever better performance power consumption and si
20. edded system is often just one of many component of a larger system e The user of the ES is often not aware that it is a computer based system e g my coffee maker or a microwave 2 2 Where are Embedded Systems Found In just about any device that is controlled by electricity In the Home Appliances Refrigerators Washers Dryers Microwaves Coffee makers Ovens Entertainment TV s DVD s Stereo s DVR s Cable boxes Remote controls Camcorders Cameras Wireless routers MP3 players Other Security systems Garage door openers Alarm clocks Exercise equipment Toys Thermostats c Kevin R Burger Computer Science amp Engineering Arizona State University Fall 2015 Page 1 CSE325 Embedded Microprocessor Systems Course Notes Part 1 Intro to Embedded Systems In the Office Fax machines Copiers Laser printers Digital telephones IVR systems Security systems Printers Environmental monitoring HVAC control In the Automobile Electronic fuel ignition Environmental monitoring ABS Instrumentation Security systems Transmission control Air bag system Climate control Keyless entry GPS navigation Communication Entertainment system Active suspension Literally Almost Everywhere ATM s Airplanes Trains Medical devices Industrial control Satellites Aerospace The list goes on and on and on aes http spectrum ieee org green tech advanced cars this car runs on code 2009 The avionics in the F 22 Raptor
21. es in the world that does not officially mandate use of the metric system When I was a kid in elementary school in the early 70 s some of our days in mathematics were filled with exercises in converting imperial units to metric units and learning about the metric system as the USA was finally in the mid 70 s on the verge of moving to the metric system That was 40 years ago and where are we at now Soda now comes in 2 liter bottles instead of the old 32 oz bottles Quite frankly I don t think America is on the whole composed of enough citizens of above dullard intelligence that we will ever be able to convert Patriot Missile Failure http www ima umn edu arnold 455 f96 disasters html During the Gulf War in 1991 an American Patriot missile system failed to intercept an incoming Iraqi Scud missile which struck an Army barracks killing 28 people The root cause was an incorrect calculation of time due to a rounding error in the fraction 1 10 The Patriot missile system was not designed to be left continuously operating without rebooting and over the course of the several days that it was the resulting roundoff error was magnified leading to the timing error Lesson It is generally not a good ideal in safety critical systems to try to work around roundoff errors Also one should try to avoid floating point data types and operations at all costs 13 4 P The Risk s Digest is an interesting read on various software failure
22. gister File Bus Interface Control Unit Cache GP processors are not commonly used in ES s because in many cases they are overkill i e offer more performance than the system requires consume too much power and or also cost more than alternative processors They also lack many of the peripheral components that ES s rely on and although these components can be added to the design they will be ex ternal to the processor and thus increase the size of the printed circuit board PCB 21 mbed https developer mbed org 22 mbed SDKhitps developer mbed org handbook mbed SDK 23 mbed HDK https developer mbed org handbook mbed HDK 24 mbed Compiler https developer mbed org handbook mbed Compiler 25 http en wikipedia org wiki Microprocessor c Kevin R Burger Computer Science amp Engineering Arizona State University Fall 2015 Page 7 CSE325 Embedded Microprocessor Systems Course Notes Part 1 Intro to Embedded Systems General Purpose Processor Microcontroller Microcontrollers are specifically designed for ES applications and 4 8 16 32 and 64 bit microcontrollers are widely used FYI Texas Instruments developed the world s first microcontroller the TMS 1000 in 1971 RAM Clocking s Oscillator Microprocessor PLL ROM 1 0 Interface Peripherals Cache Microcontrollers have numerous advantages over microprocessors in ES s Ref BERGER p 34
23. grammed value Can be used to generate a periodic waveform e g a square wave Pulse Width Modulation PWM Ref KL46 SRM TPM PWM module Ch 31 Generates a synchronous series of pulses on an output pin with programmable period and duty cycle We will use this module in CSE325 Real Time Clock RTC Ref KL46 SRM Real time clock module Ch 34 Maintains time of day and provides stopwatch and alarm functionality 38 http en wikipedia org wiki Watchdog _ timer 39 http en wikipedia org wiki Programmable_interval_timer 40 http en wikipedia org wiki Interrupt 41 http en wikipedia org wiki Input capture 42 http en wikipedia org wiki Output compare 43 http en wikipedia org wiki Pulse width modulation 44 http en wikipedia org wiki Real time_clock c Kevin R Burger Computer Science amp Engineering Arizona State University Fall 2015 Page 11 CSE325 Embedded Microprocessor Systems Course Notes Part 1 Intro to Embedded Systems 3 3 2 Input Output and Communication Communication among ES components whether inter chip intra chip on the same or a different PCB or with the external environment is an integral part of all ES s We will spend quite a bit of time in CSE325 on communication but for now here are few characteristics you should know e Communication speeds are measured in bits per second bps kilobits per second Kbps megabits per second Mbps g
24. igabits per second Gbps or terabits per second Tbps e A communication channel can be synchronous clocked or asynchronous unclocked e The direction of data transfer in a communication channel can be one direction only bidirectional but in only one direction at a time or simultaneously bidirectional e Parallel communication or transfer is the process of sending multiple bits simultaneously while serial communication or transfer is the process of sending data sequentially one bit after the other There are advantages and disad vantages to each which we will discuss later in the course Discrete or General Purpose 1 0 Ref KL46 SRM PORT and GPIO modules Chs 11 42 All microcontrollers have pins which can be configured for input or output mode The number of pins will vary from family to family and even within families One of the most important selection criteria for a microcontroller is to make sure you select one that has an adequate number of I O pins for your application We will discuss the Kinetis MKL46Z GPIO module soon Universal Asynchronous Receiver Transmitter UART Ref KL46 SRM UART modules Chs 39 40 Handles the RS 232 serial I O protocol in hardware We will discuss this module in CSE325 Inter Integrated Circuit I C or IIC or 12C Ref KL46 SRM I2C Module Ch 38 A standard serial I O protocol commonly used in ES s We will discuss this module Serial Peripheral Interface
25. ing me to wait on it One characteristic of a RTOS is that it provides consistency concerning the time it takes to recognize an event and complete the event s task handler variability in this time is referred to as jitter and for hard real time events zero jitter is the goal which cannot realistically be met so in practice the system is designed so the maximum delay is less than some epsilon where epsilon is relatively small RTOS s provide advanced scheduling algorithms for running tasks at various rates and ensuring that higher priority tasks are never preempted by lower priority tasks 3 Although in some cases the microprocessor selection is limited to a certain manufacturer because of company policy or because you already have all of the development tools you need for a certain microprocessor and switching families or vendors would result in having to purchase all new development tools http www drdobbs com a simple real time executive 184402613 http en wikipedia org wiki Real time _ operating _ system Embedded Linux is a RTOS see http en wikipedia org wiki Embedded _ Linux A preemptive system is one in which a lower priority task may be interrupted by a higher priority task which runs to completion before control returns to the lower priority task Some ES s use preemptive schedulers and some do not see http en wikipedia org wiki Preemption computing NOOO FS c Kevin R Burger Computer Scie
26. n 2nd ed Newnes 2003 Kinetis KL46 Sub Family Data Sheet Rev 5 Freescale 2014 Kinetis KL46 Sub Family Reference Manual Rev 3 Freescale 2013 Noergaard T Embedded Systems Architecture 1st ed Newnes 2005 OpenSDA User s Guide Rev 0 93 Freescale 2012 Vahid F and Givargis T Embedded System Design John Wiley amp Sons 2002 White E Making Embedded Systems O Reilly 2011 c Kevin R Burger Computer Science amp Engineering Arizona State University Fall 2015 Page 16
27. nce amp Engineering Arizona State University Fall 2015 Page 3 CSE325 Embedded Microprocessor Systems Course Notes Part 1 Intro to Embedded Systems Popular RTOS s a more comprehensive list of RTOS s can be found at INTEGRITY http en wikipedia org wiki Integrity operating system LynxOS http en wikipedia org wiki LynxOS OSE http en wikipedia org wiki Operating System Embedded QNX http en wikipedia org wiki QNX VxWorks http en wikipedia org wiki VxWorks Windows CE http en wikipedia org wiki Windows CE Embedded Linux https en wikipedia org wiki Linux_on embedded systems Embedded Linux is not exactly a RTOS but it is commonly used in ES s According to Wikipedia the primary disadvantage of embedded Linux over a RTOS is the relatively large memory footprint and a complex device drivers framework a device driver is software that interfaces to a hardware device essentially it becomes part of the OS if you tweak the right things A program running in an ES which does not use a RTOS is said to be running on bare metal In CSE325 we will not use a RTOS so our programs will run on bare metal Software failure can be catastrophic BERGER pp 9 11 NOER p 6 WHITE p 1 We touched on this when we discussed real time event response However catastrophic failures can manifest themselves in nonreal time ways Six notorious failures are discussed below Therac 25 http en wikipedia org wiki Therac
28. ncluding development and manufacturing Saving a few cents on a part can result in substantial savings over the product s lifetime For example consider two designs A and B for an device containing an ES Production volume is estimated to be 100 000 units per year with a product lifetime of 5 years Retail cost is 100 The parts for design A are 7 37 and for design B 7 36 and the manufacturing costs are otherwise identical say 12 so design A s manufacturing cost will be 19 37 and design B s 19 36 Research and development costs for both designs are the same How much savings would design B lead to over design A Number of units manufactured over the product lifetime 100 000 x 5 500 000 Manufacturing cost for design A 500 000 x 19 37 9 685 000 Manufacturing cost for design B 500 000 x 19 36 9 680 000 Gross profit 500 000 x 100 50 000 000 Net profit for design A 50 000 000 9 685 000 40 315 000 Net profit for design B 50 000 000 9 680 000 40 320 000 1 In contrast the NASA space shuttle s computer systems were relatively old fashioned and underpowered with the primary flight control software consisting of just 400 000 LOC running on a system with 1 MB of memory and a processor running at 1 4 MIPS Ref http www nasa gov mission__pages shuttle flyout flyfeature__shuttlecomputers html 2 Similar to an iPhone which of course retails for about a klokzillion dollars c Kevin
29. nt of the Apollo 11 lunar module carrying Neil Armstrong and Buzz Aldrin to the moon at 6000 feet above the surface the navigation and guidance computer began to issue code 1201 and 1203 alarms These alarms indi cated executive overflows meaning the guidance computer could not complete all of its tasks in real time and had to post pone some of them The root cause was a radar switch that was in the wrong position due to an error in the astronaut s checklist manual which caused a flood of spurious data thus leading to the executive failure Armstrong was forced to semi automatically pilot the lander while attempting to locate a boulder free area and finally landed with just 25 seconds of fuel remaining Lesson The software essentially functioned as designed and the root cause of the failure was the erroneous checklist man ual Don t let the clueless write manuals Mars Climate Orbiter http mars jpl nasa gov msp98 news mco991110 html This probe was launched by NASA on 11 Dec 1998 to study the Martian climate On 23 Sep 1999 communication was lost as the probe went into orbital insertion Ultimately the probe entered the atmosphere at an incorrectly low altitude and burned up The root cause was ground based software producing an output in Imperial units or British units instead of the metric units which the probe was expecting Lesson The United State is along with those bastions of freedom Burma and Liberia one of only three countri
30. r destroying connections between wires that connect gates to implement the design Unlike ASIC s which must be fabricated by an IC fab a PLD is user programmable i e the design does not have to be sent to a fab Field Programmable Gate Arrays FPGA s are a particular type of programmable logic device that have become extremely popular since the early 1990 s They are essentially user programmable gate array ASIC s You will learn all about these in CSE320 Advantages of PLD s and FPGA s are low NRE costs user programmability quick turnaround time and flexibility Disadvantages are that they will achieve lower performance than an VLSI or ASIC design will be larger will consume more power and will have higher unit costs Often an FPGA will used during prototyping to prove the design before final implementation in VLSI or an ASIC 3 2 Storage 3 2 1 Read Only Memory ROM ROM stores bits instructions and data permanently when the system is powered off Various types of ROM have been developed over the years and we will discuss memory technology in more detail later in the course so this is just a high level overview Mask ROM A ROM designed and manufactured at the transistor level A fab will build these for you Programmable ROM PROM Similar to a mask ROM but user programmable Most PROM s are one time programmable Erasable Programmable ROM EPROM A PROM that can be erased and reprogrammed multiple times Erasure is pe
31. rformed by exposing the chip to UV light Electrically Erasable Programmable ROM EEPROM An EPROM that can be erased by applying current to the transistors Flash Flash ROM is a form of EEPROM that is very similar but also different than traditional EEPROM 36 http en wikipedia org wiki Gate array 37 http en wikipedia org wiki Field programmable_gate _ array c Kevin R Burger Computer Science amp Engineering Arizona State University Fall 2015 Page 10 CSE325 Embedded Microprocessor Systems Course Notes Part 1 Intro to Embedded Systems 3 2 2 Random Access Memory RAM RAM stores bits instructions and data for a program which is currently being executed The primary difference from ROM is that RAM will lose its contents when power is removed RAM is volatile There are as many or more types of RAM than there are ROM RAM is broadly classified into two categories static RAM SRAM and dynamic RAM DRAM The basic difference between the two is that SRAM is generally faster less dense stores fewer bits per mm and more expensive than DRAM 3 3 Peripherals Peripherals are components that provide various functionality that is often required in an ES These are called peripherals because historically the chips were located outside the microprocessor chip Microcontrollers have peripherals embedded on the same die as the microprocessor and this is why microcontrollers have become so popular in th
32. s Power constraints BERGER 9 11 VAHID 1 1 WHITE 1 ES s often run on batteries or in environments where something like this is not feasible that is a huge heat sink and a fan sitting on top of a microprocessor cooling it down In some ES s the batteries are nonrechargeable because they are not easily accessible and the system must run for months or years on battery power 11 Imagine the carnage that would take place on the roads And I m being optimistic 12 1 10 has a nonterminating binary expansion 13 http catless ncl ac uk Risks c Kevin R Burger Computer Science amp Engineering Arizona State University Fall 2015 Page 5 CSE325 Embedded Microprocessor Systems Course Notes Part 1 Intro to Embedded Systems Environmental conditions BERGER pp 9 12 ES s are found miles underwater on mountaintops underground and in space Some may need to operate in temperatures ranging from 200 degrees C to 100 degrees C They must be designed to handle moisture pressure acceleration high g forces and other factors that no desktop PC will ever experience Fewer resources than a desktop system BERGER pp 9 13 WHITE pp 1 4 I got a new office computer this year It s a Dell latitude laptop with a 2 GHz Intel i7 processor 16 GB of RAM and a 256 GB solid state drive It has a 14 touch LCD about a thousand keys on the keyboard a touchpad and a host of external interfaces e g ethernet USB firewire
33. s 1 and 2 to study Mars and its moons Phobos 1 launched on 7 July 1988 and operated normally until controllers lost communication with the probe The root cause was a bug in software uploaded on 29 Aug which deactivated the attitude thrusters This caused Phobos 1 to lose its lock on the Sun which was critical for aligning the solar arrays to charge the batteries and eventually the batteries failed and the probe was lost Interestingly the software which turned off the attitude control was intended to only be used during test ing on the ground However the software was coded in PROMS and so removing the test code before launch would have required removing and replacing the entire computer system Because of the time pressure from the impending launch a decision was made to leave the code intact knowing that it would never be activated During the software upload on 29 Aug a single character error resulted in the offending code being executed 10 Lesson See 8 http en wikipedia org wiki List_of _ real time operating __ systems 9 Approximately 3 times larger 10 http en wikipedia org wiki Murphy s _law c Kevin R Burger Computer Science amp Engineering Arizona State University Fall 2015 Page 4 CSE325 Embedded Microprocessor Systems Course Notes Part 1 Intro to Embedded Systems Apollo 11 Lunar Module http www hg nasa gov office pao History alsj al1 a11 1201 pa html During the desce
34. ved to be the next great programming language and the lan guage to end all languages This never came to pass and today Ada is mainly used only in military and aerospace appli cations FORTH I like FORTH and it has a small but devout following in the ES community but it s not very popular 4 System on Chip SoC and System in Package SiP Design SoC stands for either system on chip or system on a chip Regardless of which you prefer the intent is the same to squeeze pretty much an entire computer system onto a single chip According to the first SoC was constructed in 1974 to power a Microma digital watch but it was not until the last ten or so years that SoC s have become widely used specifically in the smart phone and pad computer markets An SoC will contain one or microprocessors and or microcontrollers and some or all of these components e Other application specific digital circuits e A digital signal processing DSP core this is a form of ASIP e Memory RAM ROM EEPROM or flash e A graphics processing unit GPU e Clocking sources oscillators and PLL s e Various peripherals e g timers counters real time clocks PWM e External I O interfaces e g Ethernet UART Firewire USB C SPI SATA GPIO HDMI memory e A D and D A converters e Voltage regulators and power management circuits e Analog and mixed signal circuitry including RF circuitry e Interconnect circuitry i e
35. vin R Burger Computer Science amp Engineering Arizona State University Fall 2015 Page 12 CSE325 Embedded Microprocessor Systems Course Notes Part 1 Intro to Embedded Systems 3 3 3 Direct Memory Access DMA Ref KL46 SRM DMA module Ch 23 A feature in many microprocessor and microcontroller systems which permits hardware devices other than the CPU to access system memory and transfer blocks of data from and to memory with little processor interaction 3 3 4 Interrupt Controller Ref ARM M0 DUG NVIC module 4 2 An interrupt is an event either hardware generated or software generated that interrupts the microprocessor s normal execution sequence and causes it to execute the code of an interrupt service routine ISR Interrupts are very common and extremely useful in all computer systems so we will spend quite a bit of time discussing the ARM Nested Vector Interrupt Controller NVIC module 1 3 5 Analog to Digital and Digital to Analog Conversion Ref KL46 SRM ADC module Ch 28 DAC module Ch 30 Various analog sensors or transducers can be used to interface with the external environment e g a temperature sensor Since the real world is analog continuous e g temperature voltage light intensity but computers are digital there must be a way to convert an analog signal to digital or vice versa An A D converter or ADC is a circuit which converts a continuous analog signal into a stream of digital
36. want to play around with it if you are interested Note however that this would require flashing new firmware to the K20 debug chip on the FRDM KL46Z board that would support the mbed tools the firmware currently contains code to support the OpenSDA protocol High availability Some ES s must run continuously for months or years without being powered down or if they are powered down it may be for only a very short time e g consider an implanted medical device such as a pacemaker or insulin pump 3 Overview of ES Components 3 1 Processors You all know what a microprocessor is so I won t spend anytime discussing that Suffice it to say it wouldn t be an ES without a processor of some sort 3 1 1 Processor Taxonomy There are several different types of processors used in ES s General Purpose Processor Microprocessor Ref VAHID p 1 5 A general purpose GP microprocessor is designed to be used in a wide variety of designs laptops desktop systems supercomputers pad computers ES s with a primary goal being to maximum processor sales for the manufacturer which is accomplished by selling the chips in large volume hence they must be very versatile Intel s Pentium Celeron Atom Core Core 2 and Xeon chips and AMD s Athlon Sempron Turion Opteron and Phenom chips which are used in almost all desktop laptops and supercomputers are examples of general purpose processors Major components Datapath ALU Re
37. y Fall 2015 Page 14 CSE325 Embedded Microprocessor Systems Example SoC Apple A8 The Apple A8 first appeared in the iPhone 6 and iPhone 6 Plus smart phones in 2014 Apple likes to be keep its technology a secret but these features are known to be present SiP stands for either system in package or system in a package Regardless of which you prefer the idea is similar to SoC but rather than cramming the entire system on one chip the system is composed of two or more chips which are arranged to form a package The following image illustrates different SiP package technologies used by Renesas The fourth picture above shows the package on package technology in which two packages are stacked one on top of the other Commonly PoP will be used to stack two memory packages or stack an SoC on the bottom which is in a Dual core 1 38 GHz 64 bit ARMv8 A core Course Notes Part 1 Intro to Embedded Systems PowerVR 6XT GX6450 quad core GPU hardware accelerator for audio and video applications 1 GiB of low power DDR3 dynamic RAM 64 KiB instruction and 64 KiB data L1 cache 1 MiB shared L2 cache 4 MiB L3 cache Feature size 20 nm Two billion transistors Structure Advantage Flexibility of Memory vender High Density Cost Chip Stack a Small and High density Circuits E pora Side by Side a z Good heat n m Ps QFP J PoP Package on Package z High Flexibility of
38. ze compared to a GP processor 28 e In large volumes unit costs may be low Disadvantages include e Nonrecurring engineering NRE cost may be high compared to a commercial off the shelf COTS chip e Flexibility is low e g if a bug is found or new features are added the chip may need to be redesigned and retested e In small quantities unit cost may be high 26 http en wikipedia org wiki TMS _1000 TMS 1000 27 VLSI Solution VS101le MP3 Decoder Chip http www vlsi fi fileadmin datasheets vs1011 pdf 28 Manufacturing cost 29 NRE cost is what it costs the company to design and develop the chip It is a one time expense hence nonrecurring although it could be quite large 30 A COTS chip is one that someone else has designed manufactured and is selling They have paid the NRE and unit costs for the chip and are attempting to gain back these costs and to make a profit by selling the chip in volume c Kevin R Burger Computer Science amp Engineering Arizona State University Fall 2015 Page 8 CSE325 Embedded Microprocessor Systems Course Notes Part 1 Intro to Embedded Systems Application Specific Instruction Set Processor ASIP Ref VAHID p 1 7 The goal of using an ASIP is to try to gain the advantages of using both a general purpose and special purpose processor without the disadvantages of each Whereas a single purpose processor is not really program mable the hardware is the program
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