Circle6 the other edge of the sclk line rising or

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circle6 The other edge of the SCLK line (rising or falling) signals the devices to register the bits on the MOSI and MISO, effectively reading the bit into the device.
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Basic Transmission Step-by-Step circle6 The transmission continues in this fashion until the devices have exchanged the specified number of bits (usually 8,16, or 32) circle6 After the transmission is complete the Master pulls the SS line for the slave back high and either goes to another slave on the network or reinitiates the transmission with the same slave by pulling the corresponding SS line back to low.
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Flowchart of the basic SPI transmission
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Daisy chain SPI configuration
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Daisy chain SPI configuration circle6 The first slave output being connected to the second slave input, etc. circle6 The SPI port of each slave is designed to send out during the second group of clock pulses an exact copy of what it received during the first group of clock pulses. circle6 The whole chain acts as an SPI communication shift register; circle6 Daisy chaining is often done with shift registers to provide a bank of inputs or outputs through SPI . circle6 Such a feature only requires a single SS line from the master, rather than a separate SS line for each slave circle6 Applications (discussed later) that require a daisy chain configuration include SGPIO and JTAG
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Strengths and Weaknesses of SPI Strengths circle6 Widespread support and IP available circle6 Full duplex communication circle6 Higher throughput than I²C or SMBus circle6 Complete protocol flexibility for the bits transferred (i.e. Not limited to 8-bit words) circle6 Simple Protocol to implement and understand circle6 Typically no external circuitry required (like pullup resistors for I²C) circle6 System clocked by a master meaning that precision oscillators and PLL not needed circle6 Addressing not needed (decreases complexity and helps throughput by not sending an address for each communication) circle6 Transceivers are not needed circle6 Serial protocol use fewer physical connections than parallel interfaces circle6 Mostly shared lines for multiple devices (except the separate SS lines for each device)
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Strengths and Weaknesses of SPI Weaknesses circle6 No standards body governs SPI as an official protocol circle6 The more devices you have the more pins and connections necessary circle6 No hardware flow control circle6 No hardware slave acknowledgment (the master could be "talking" to nothing and not know it) circle6 Does not support a multi-master architecture circle6 Only handles relatively short distances (meant for on-PCB communication mostly)
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Applications SPI is used to talk to a variety of peripherals, such as: circle6 Sensors: temperature, pressure, ADC, touchscreens circle6 Control devices: audio codecs, digital potentiometers, DAC circle6 Camera lenses: Canon EF lens mount circle6 Communications: Ethernet, USB, USART, CAN, IEE 802.15.4, IEEE 802.11 circle6 Memory: flash and EEPROM circle6 Real-time clocks circle6 LCD displays, sometimes even for managing image data circle6 Any MMC or SD card (including SDIO variant)
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I2C & SPI – A Comparison Reference : Application Note AN4024 from Maxim
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UART – Introduction circle6 A Universal Asynchronous Receiver/Transmitter (UART) is a type of "asynchronous receiver/transmitter", a piece of
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