arm iq cortex-m0

Download Arm Iq Cortex-m0

Post on 10-Apr-2018




0 download

Embed Size (px)


  • 8/8/2019 Arm Iq Cortex-m0


    The Smart Approach to Designing with the ARM Architectu

    Volume 8, Number 1, March 200Infor mation Quar ter ly

    The New

    ARM Cortex-M0


    Meeting the Demandsof Low Power Applications

    Low Power Design using the LPC1100 Series, A Methodology forLow Power Verification, Power Management for Optimal Power Design

    PLUS: Techniques for Optimization of Audio CodecsProviding a Clear Vision for Home Entertainment, Printer with an Attitude and MORE!

    The New

    ARM Cortex-M0


    Meeting the Demandsof Low Power Applications

    Low Power Design using the LPC1100 Series, A Methodology forLow Power Verification, Power Management for Optimal Power Design

    PLUS: Techniques for Optimization of Audio CodecsProviding a Clear Vision for Home Entertainment, Printer with an Attitude and MORE!

  • 8/8/2019 Arm Iq Cortex-m0


    ARM Cortex-M0


    This special section introduces the ARM Cortex-M0, thesmallest, lowest-power, and most energy-efficient ARMprocessor available. The exceptionally small silicon area,

    low-power and minimal code footprint of the processor enablesdevelopers to achieve 32-bit performance at an 8-bit price point.

    The articles in this section include:

    ARM Cortex-M0 Processor Introduction By Dominic Pajak, ARM

    The NXP LPC1100 ARM Cortex-M0 MCUs By Rob Cosaro, NXP

    Low Power Design using the LPC1100 Series By Rob Cosaro, NXP

    ARMCortex-M0ProcessorMeeting the demandsof tomorrows low

    power applications


    Reprinted from ARM IQ with permission of Convergence Promotions.

  • 8/8/2019 Arm Iq Cortex-m0


    By Dominic Pajak, ARMAs the cost of energy continues to grow, and concern aboutthe environment matures, the increasing penetration of embed-ded devices into everyday lives presents developers with thechallenge of managing the trade off between the demands forperformance and low-power. Traditionally 16-bit microcon-trollers have been used to provide the low-power consumptionrequired, but in today's applications their lack of performanceefficiency can mean shorter battery life. To meet this challengeARM has developed a processor combining the performanceof 32-bit, with the lower power and gate count normallyassociated with 16-bit processors.

    The demand for ever lower-cost products witincreasing connectivity (e.g. USB, Bluetooth, IEEE 802.15) andsophisticated analog sensors (e.g. accelerometers, touchscreens) has resulted in the need to more tightly integrateanalog devices with digital functionality to pre-process andcommunicate data.

    Most 8-bit devices do not offer the performance to sustain thestasks without significant increases in MHz and therefore power,and so embedded developers are required to look for alternativedevices with more advanced processor technology. The 16-bit

    devices have previously been used to address energy efficiencyconcerns in microcontroller applications. However, the relativeperformance inefficiencies of 16-bit devices mean they willgenerally require a longer active duty cycle or higher clockfrequency to accomplish the same task as a 32-bit device.

    The 32-bit ARM Cortex-M0 processor has been developed toaddress this need for increased performance efficiency whileremaining very low-power, making it ideal for the nextgeneration of ultra low-power MCUs and precision analogdevices.


    ARM Cortex-M0

    The new Cortex-M0Processor further extendsARMs MCU roadmap intoultra low-power MCU andSoC applications including: Gaming accessories

    Lighting Motor Control e-Metering Smart control Analog and Mixed Signal Power Control Medical Devices Zigbee & Z-Wave Systems

    Introduction to theARM Cortex-M0


    Reprinted from ARM IQ with permission of Convergence Promotions.

  • 8/8/2019 Arm Iq Cortex-m0


    ARM Cortex-M0

    ARM Cortex-M0 Processor. The ARM Cortex-M processorfamily is specifically designed to address the needs of deeplyembedded applications that require low-power and fastinterrupt response, making it ideal for microcontrollers. Theflagship processor in this range today is the ARM Cortex-M3,offering superior performance and features. The new ARM

    Cortex-M0 complements this by enabling silicon vendors tooffer devices with an upwards compatible subset of the ARMCortex-M3 features at an even lower area and power.

    The ARM Cortex-M0 processoris a 32-bit RISC processor capableof 0.9 DMIPS/MHz that implementsa small instruction set architecture(ISA) that consists of less than 60instructions. This simple ISA is asuperset of the 16-bit Thumb ISAfirst implemented in the ARM7TDMI

    processor, and has subsequentlyunderpinned the ISA of every ARMprocessor developed since (formore information on the ISA, seeConclusion).

    The reason for the enduringpopularity of Thumb lies in itscode density - this is crucialin embedded devices where thememory footprint can be the mostsignificant proportion of the silicon cost. The small gate countof the Cortex-M0 (12K gates in the minimum configuration)makes it ideal for low cost devices on the larger silicon processtechnology nodes used in the manufacture of microcontrollerand mixed-signal devices (for example 0.35m, 0.25m,0.18m). Incredibly the ARM Cortex-M0 can achieve compara-ble performance efficiency to the ARM7TDMI in just a third ofthe size and power.

    Minimizing device power consumption. Within a microcontrollerdevice the processor logic accounts for a proportion of thetotal current drawn in active or sleep states. In a typical

    configuration, running at 1.8 Volts on a 180ULL (Ultra LowLeakage) process implemented using ARM standard celllibraries the ARM Cortex-M0 processor contributes as little as50A/MHz to the active current (depending on the implementa-tion approach and process technology used).

    The processor is not the only consumer of power within adevice, and there are a many other functions within themicrocontroller that must also be carefully tuned to achievetruly ultra low-power (memory and peripheral system

    organization and implementation, clock generation, voltagescaling, etc.) - this is the domain of ARM silicon partners andwill be covered in the next section. However the processor alshas a significant effect on the power consumed by peripheralsand memory which will be accessed during activity periods (foexample, the smaller code size possible with Thumb can reduc

    power consumed by flash memory access).

    Minimizing the active current also broadens the type of energysource applicable for the applications, enabling energy to be

    sourced from smaller, cheaperbatteries and also potentiallyrenewable energy harvestingsources. Reducing powerconsumption can also have thebenefit of reducing the powersupply complexity.

    Reducing System Power. Digital

    processing at the sensor nodecan be an effective strategy inreducing the energy consumptionof a system. For example,compression, filtering or analysisof analog sensor sample data atthe node can significantly reducethe activity of the RF transceiverin a IEEE 802.15 wireless sensor

    In an optical heart rate monitorapplication this can mean that only a BPM (beats per minute)

    value needs to be communicated wirelessly, not the entiresensor sample stream. Another example is interpreting datafrom an analog sensor to ensure the higher performanceapplications processor within a system is only woken whenthe user needs to interact with it (e.g., waiting for a deliberatetouch on the screen before communicating input to the hostprocessor and waking a smart phone). In automotiveapplications, the increasing number of sensors and actuatorspresent in a vehicle means the CAN bus is rapidly reachingcapacity - increasing device intelligence can alleviate thisthrough a reduction in communication traffic. These are allapplications that can greatly benefit from increased processing

    capability that the Cortex-M family of processors can providewhen closely coupled with an analog sensor source.

    Measuring Energy Efficiency. A common strategy to reduce theenergy consumption of a microcontroller is to put it into alower power sleep mode whenever possible, and wake it onlywhen necessary. The energy consumption is considered as theaverage current of these different activity and sleep states.

    Designing for Ultra Low-Power

    Reprinted from ARM IQ with permission of Convergence Promotions.

  • 8/8/2019 Arm Iq Cortex-m0


    ARM Cortex-M0

    (Figure 1, page14, illustrate the concept; in practice the activeduty cycle can be lower than 0.05% in an IEEE 802.15 basedwireless system, and the active current may be exponentiallylarger than the sleep current of a device.)

    To estimate the average current there are three variables that

    must be considered; the Active Duty Cycle(i.e., what percent-age of the time is the device active), the Active Currentand theSleep Current. When choosing a low-power microcontroller theprocessor has an impact on these variables. In the followingsections we will see how ARM Cortex-M0 has been designed toaddress all three.

    A significant benefitof ARM Cortex-M0 (and the higher performance Cortex-M3)over 8- or 16-bit architectures is performance efficiency theability to complete tasks faster and therefore reduce activityperiods. The performance advantage stems from Cortex-M0

    being able to perform single cycle 32-bit arithmetic and logicoperations (including single cycle 32-bit multiplication) andalso perform 8-bit, 16-bit or 32-bit data transfers with indexedaddressing in a single instruction. This can have a dramaticeffect in reducing the processor clock frequency required, andfurthermore also reduces the memory required to store theassociated progr


View more >