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Serial Buses. Serial Bus Features. Allows several devices to be connected to a set of common signal wires Reduces inter-connections and complexity Asynchronous or Synchronous Master - Slave(s) Multiple Masters Standard interfaces and protocols
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Serial Bus Features Allows several devices to be connected to a set of common signal wires Reduces inter-connections and complexity Asynchronous or Synchronous Master - Slave(s) Multiple Masters Standard interfaces and protocols Various bus operation speeds (data rates/ baud rates) various application areas
Serial data communication • Synchronous • use a shared common clock signal. • all devices synchronise with the shared common clock signal. • data transfer occurs on the clock signal – usually a clock transition. • Asynchronous • no shared clock • all devices have there own clock • all devices must use the same clock frequency • Tx and Rx clock frequencies may differ slightly between devices • device clock signals are out of phase with each other – not synchronised hence the term asynchronous. • the receiver must synchronise with transmitter in order to receive data correctly.
Baud Rate • The baud rate of a data communications system is the number of symbols transferred per second. • Bit rate defines the rate at which information flows across a data link. measured in bits/second(bps) • For a binary two-level signal, a data rate of one bit per second is equivalent to one Baud Note: For a binary signal - Baud rate = bit rate = 1/bit time 11 In this case: Bit rate = 2 x Baud rate Data 10 01 T T = The Bit Time 00 Time 00 01 11 10 11 00 01 The baud unit is named after Jean Maurice Emile Baudot, who was an officer in the French Telegraph Service.
Some common serial buses SPI- Serial Peripheral Interface I2C - Inter-Integrated Circuit RS232 - Computer serial port(point to point only) USB - Universal Serial Bus Ethernet - high speed LAN CAN - Control Area network LIN - Local Interconnect Network FlexRay - FlexRay is a fault tolerant bus and provides deterministic data transmission. MOST - Media Oriented Systems Transport MIL-STD-1553 Bus - military avionics & spacecraft
Applications • Chip to Chip connections • SPI and I2C • Processing node to peripheral devices • USB • SPI & I2C • LIN • Processing node(Computer System) to processing Node • Ethernet • CAN
Classification of Serial Bus Systems http://www.steinhoff.de/images/fb_class.pdf