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Circle6 it is up to the master and slave devices to

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circle6 It is up to the master and slave devices to know whether a received byte is meaningful or not. circle6 A device must discard the received byte in a “transmit only” frame or generate a dummy byte for a “receive only” frame. circle6 SPI does not have an acknowledgement mechanism to confirm receipt of data. circle6 SPI is better suited to applications in which devices transfer data streams such as the communication between a “codec” (coder-decoder) and a digital signal processor. Reference : Introduction to Serial Peripheral Interface from Embedded Systems Design
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SPI Bus – Signal Lines The four typical SPI signals include: Serial clock (SCLK) - This signal is generated by the Master. - Other signals in the transmission change based on the timing of edges from this clock. Data is typically output from the transmitter during the falling edge of SCK. Data is typically latched by the receiver during the rising edge of SCK. circle6 master data output, slave data input (MOSI) - This line is the output from the Master to the slave. - Transmits bit-by-bit synchronized with Master clock edges.
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SPI Bus – Signal Lines master data input, slave data output (MISO) -This line is the output from all the slaves connected. - Transmits bit-by-bit from the slave synchronized with Master clock edges. chip select (CS) or slave select (SS) - This is a bank of signals where each line goes to individual slaves in the system. - One line is asserted at a time to enable communicate with the corresponding slave. When this signal goes low, the slave will listen for SPI clock and data signals.
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Master connected to one slave
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SPI Bus – Typical SPI Connection Reference : AT25512 SPI Serial EEPROM from Atmel
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Data Transmission circle6 A typical hardware setup using two shift registers to form an inter-chip circular buffer circle6 the master first configures the clock, using a frequency less than or equal to the maximum frequency the slave device supports. circle6 Such frequencies are commonly in the range of 1-70 MHz. circle6 The master then pulls the slave select low for the desired chip circle6 With the SPI interface you can communicate with a device transmitting and receiving 8 bits of data at the same time and it is suited to high speed streaming data transfers.
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Data Transmission During each SPI clock cycle, a full duplex data transmission occurs: circle6 the master sends a bit on the MOSI line; the slave reads it from that same line circle6 the slave sends a bit on the MISO line; the master reads it from that same line circle6 Not all transmissions require all four of these operations to be meaningful but they do happen.
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Basic Transmission Step-by-Step circle6 The Master drives a particular SS line low to initiate communication with the corresponding slave. circle6 Once the selected SS is low, one edge (rising or falling) of the SCLK signals the devices (Master and Slave) to toggle the MOSI and MISO to the correct bit of data being transmitted.
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