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SERIAL AND PARALLEL PORTS

Parallel Port

The parallel port functions by sending its information in parallel signal wires by sending the signal through a group of separate wires. All the bits in a group are handled exactly at the same time. Typically they have eight data lines one or more handshaking lines. The term handshaking includes a number of functions needed to coordinate the data transfer.




The centronics standard is commonly used for sending parallel data to printer.

 

Serial port

In serial signaling each of the bits is sent in turn, according to an agreed sequence, over a single channel or wire. The concept behind serial communication is as follows,

Data is transferred from sender to receiver one bit at a time through a single line or circuit.

The serial port takes 8, 16 or 32 parallel bits from the computer bus and converts it as an 8,16 or 32-bit serial stream.

 

The name serial communication comes from this fact each bit of information is transferred in series from one location to another. There are two types of serial communication.

i)                    Synchronous data communication
ii)                  Asynchronous data communication

RS-232 is the standard used in serial data communication. It was created for one purpose to interface between Data terminal equipment (DTE) and Data communication equipment (DCE) employing serial binary data interchange. So as stated the DTE is the terminal or computer and the DCE is the modem or other communication device. RS-232 was original adopted in 1960 by the Electronic Industries Association (EIA).

Serial signaling makes it possible to send multi-bit binary coded data over a single digital channel. In theory you would think that the parallel port would be 8 times faster, but in practice, the speed increase is much greater, since there is no wait time for encoding and decoding of the serial signal. Today’s simple parallel ports typically sends their data at 115,200 bits per second and new enhanced ports will go up to 100 times faster.

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