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Compare Parallel transmission with Serial transmission



General
  • Both Transmissions (Parallel and Serial) are used to connect peripheral devices and enable us to communicate with these devices
  • Since these systems were developed in the 1970s and 1980s these are legacy systems and have been replaced by usually USB


Serial Transmission
  • The serial transmission usually consists of 9 pins that connect the data in a series, thats why the name serial port
    Serial_port.jpg
    A serial Port with 9 pins
  • The port is based on the model of the parallel transmission, however the 9 pin model had taken off before the 25 pin model (parallel transmission) could be implemented in most computers.
  • The serial port is similar to ethernet cables and was therefor used in the 1980s to connect terminals and other devices to the computers
  • The communication the serial transmission only goes over 3 wires
    • The ground signal
    • One wire that sends
    • and one wire that receives
  • This allows communication in both directions at the same time
  • Nowadays the standard speed of serial transmissions is given at 115 KB per second
  • In order to keep the signal from making errors, at the end of every transmission a partly bit is sent
    • A Partly Bit is a bit that is end in he end that is there to make sure that the connection is not faulty
    • If it is sent and return incorrect then the computer knows that there is a error with the connection
  • Due to the simplicity if the connection a shielded connection can be transferred over 75 meters (250 feet), far more than a parallel transmission could.
  • Due to the age serial transmissions are not seen as legacy ports and are not implemented frequently anymore

Parallel Transmission
  • The most common type of parallel connector consists of 25 connectors and was implemented in 1970
    Parallel_port.jpg
    A parallel port with 25 pins
    • There are other types of parallel connectors that use either 36 or 50 pins
    • originally parallel interface only allowed transfer in one direction until the IEEE 1284 standard was created increasing distance and allowing bi-directional transfer
  • Because of the many pins, 8 bits can be transferred at once allowing a much faster transfer of information
  • The 25 connector interface consists of 17 signal lines and 8 ground lines
    • The signal lines are divided into
      • 4 control lines which which are used to initiate the handshaking
      • 5 status lines which are used to communicate the state of the peripheral devices and are used to indicate errors
      • and 8 data lines are used to transfer the data.
  • This interface allows a transfer rate over over 1 MB per second
  • Due to the old age of the parallel port it is now consider a legacy port and is only rarely implemented



Created by: Daniel Gillo
Last modification: 13th January 2011

Sources