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  • What's New with the I3C Standard

    This month we've seen both Apple and Samsung announce their newest, flagship smart phones, and they each have an incredible number of sensors and components included like:
    • Accelerometer
    • Mqgnetometer
    • Gyroscope
    • Proximity
    • Altimeter
    • Compass
    • Near Field Communication
    • Fingerprint
    • Touchscreen
    • ADC

    So one engineering challenge is how to most efficiently connect all of these components to an SoC with a minimum of wires and control signals required. The good news is that the MIPI Alliance has figured this out and created the I2C bus interface used by many SoC design companies, and even better news is that the successor called I3C is now available. Paul Kimelman from NXP spoke last week in a webinar all about I3C and how it is upwardly compatible with the previous I2C bus interface. Mr. Kimelman is one of the primary spec authors for I3C, along with Qualcomm and Intel. Other I3C spec contributors include: Invensense, TI, STMicroelectronics, Synopsys, Cadence, Mentor, Sony, Knowles and Lattice Semi,

    Article: Smart mobile SoCs: Qualcomm-sensors-min.jpg

    So what does I3C give you beyond I2C?

    The answer: Fewer GPIO wires, higher data speeds, backwards compatibility, standard IO pads, lower power usage. Here's a quick comparison chart between I2C and I3C features:

    FeatureI2CMIPI I3C
    Clock Speed & Data RateFast mode: 400kb/s
    Fast mode+: 1Mb/s
    High speed: 3.4Mb/s
    SDR: Up to 11Mbps actual Data rate
    HDR-DDR: 20Mbps actual data rate
    HDR-TSP: ~30Mbps actual data rate
    # wires2 - multi-drop
    SCL: Clock - from master(s), slaves stretch
    SDA: data - bidirectional
    2 - multi-drop
    SCL: clock - from current Master only
    SDA: data - bidirectional
    PowerHigh due to open-drain SCL, SDA with strong pullupsLower due to SCL being push-pull only and SDA working in push-pull most of the time
    Slave Read TerminationMaster has to end ReadSlave ends Read, but Master may terminate early
    In-Band InterruptsNone - use a separate wire/pin per slaveIntegrated, prioritized and may include a byte of context
    Hot-PlugNone - proprietary systems onlyBuilt-in. Same mechanism as in-band-interrupt
    Error detectionNo protocol inherent error detectionMaster and slave side error detection standardized, mandated
    Time stampingHas to be done by Master once separate INT signal is triggeredIs an essential part of the spec, no dedicated INT signal required
    Built-in CommandsNone. Proprietary messages onlyBuilt-in for control, discovery, bus management, etc.
    Master/SlaveMaster-Slave, Multi-master optionalMaster-Slave, Master handoff
    IO padsI2C special padsStandard pads 4 mA drive
    Slave addressStaticDynamically assigned during initialization. Slaves may have I2C static addresses at start
    ClockingSlaves use inbound clock or oversamplingSlaves use inbound clock
    ComplexityLow for Slaves. Higher for MastersFull Slaves ~2K gates
    Masters ~2.5K gates State machine or processor implementations




    With I3C you can expect lower power by 3 to 8X depending on data rates:

    Article: Smart mobile SoCs: Qualcomm-energy-consumption-min.jpg
    Data rates are greatly increased with I3C compared to I2C, and this chart shows the four raw bitrates possible: Article: Smart mobile SoCs: Qualcomm-raw-bitrates-min.jpg
    Write and read data for a I3C message look similar to I2C message:
    Article: Smart mobile SoCs: Qualcomm-i3c-message-min.jpg
    Address arbitration is updated with I3C for use in:
    • In-band interrupt
    • Hot-join
    • Bus initialization to assign dynamic addresses
    • Multi-master request


    The I3C specification is at version 1.0 today, however if you want to see what's coming up next in version 1.1 the list includes:
    • Group addressing
    • Multi-lane
    • In-band HW reset
    • HDR-DDR mode Slave side Write termination
    • HDR-TSP mode ability to terminate data transfer


    Warren Savage from Silvaco spoke next about semiconductor IP and how IPextreme (acquired by Silvaco) has worked with NXP for the past 10 years to make captive IP into licensable IP. Using that approach NXP has some 50 IP products now. Article: Smart mobile SoCs: Qualcomm-ipextreme-min.jpg
    The applications for I3C are quite diverse into multiple industries:
    • Medical
    • Wearables
    • Touchscreen
    • Automotive sensors
    • Audio
    • Home automation
    • Instruments


    You can even get UVM-based VIP (Verification IP) from Avery Design Systems as an add-on. Silvaco also offers you an FPGA debug environment to test out your I3C compatibility.

    Article: Smart mobile SoCs: Qualcomm-fpga-debug-min.jpg

    Webinar

    You can watch the complete webinar, lasting about an hour including the Q&A session online here. I'm really impressed at how effective the MIPI Alliance has been in creating both the I2C and I3C standards for our SoC community to leverage, resulting in consumer and industrial products delivered in record time.