Printer Plug in How Parallel Ports Work

Printer Plug-In: How Parallel Ports Work

How Printer-Plug-Ins Work

Printer-Plug-in: How Parallel Ports Work

The purpose of this paper is to thoroughly explain how printer plug-ins, specifically those connected to a parallel port works.

There are several types of methods of transmission of data from a computer to a printer. The types of connections that may be utilized are the serial port, the USB port, and the parallel port as well as others not mentioned. The parallel port is one specific way that a printer connects to a computer and is the way that the computer communicates the print job to the printer. Originally developed by IBM for use with Centronics printers the method sought was on in which the same port interface on the printer was not used on the computer.

As an alternative the engineers that worked for IBM decided instead take a DB-25, or a 25-pin connector coupled with a Centronics 36-pin connector in the creation of a cable especially made to connect the computer and printer to each other. Afterward the Centronics interface was utilized by other manufacturers of printers and the result was the status of being "standard" for this unusual connection. Data is sent to a printer from a computer or other connecting device through the use of a parallel port which sends eight (8) bits of data and does so one in increments of one byte at a time. The transmission of the 8 bits of data is accomplished in a manner that is at a parallel one to the other instead of the alternative method of the eight bits going across a serial transmission. Serially transmitted data is where the data is sent across the connection in a single row and is done so through a port called a serial port. Generally between 50 and 100 kilobytes of data is transmitted per second over a serial transmission.

As stated there are 25 pins on the connector and they are utilized as follows:

Pin One: The strobe signal is transmitted via this pin at a level between 2.8 and 5 volts however when the computer transmits a byte of data and the voltage dip is the signal that lets the printer know data is on the way.

Pin Two: through Pin Nine are the pins responsible for transmitting the data itself. In informing the printer that a bit value of 1 is present five volts of charge is transmitted through the pin. If there is not a charge on a pin that is signaled with a volt of zero. This is an efficient method of transmission of information that is digital across an analog cable effected in real-time.

Pin Ten: This pin has the responsibility of sending the signal that acknowledges that the printer has received the transmission from the computer. It operates as does Pin One in that the charge is maintained and voltage drop to that below 0.5 volts in signaling the computer that receipt of the data has taken place.

Pin Eleven: This pin receives a charge only if the printer is busy thus charging pin eleven and maintains this charge until the voltage goes below the 0.5 voltage level in signaling the computer acknowledging receipt of the data.

Pin Twelve: Pin Twelve is only signaled at the point in time that the paper has been depleted in the printer.

Pin Thirteen: Pin Thirteen services the purpose of signaling the computer that the printer is online

Pin Fourteen: This is the 'auto feed' signal sent to the computer by the printer and utilizing a voltage charge of 5.

Pin Fifteen: Voltage drop to under 0.5 on this pin signals to the computer that an error exists at the printer.

Pin Sixteen: This pin is only utilized if the computer through remote removes the printer from online status to that of offline status.

Pin Eighteen through Twenty-Five: These pins are used as grounding for the connection and are all under 0-5 volt charges.