No longer was the consumer required to purchase an expensive SCSI card-they could simply use their built-in parallel interface. This included scanners, tape drives, hard disks, computer networks connected directly via parallel interface, network adapters and other devices. Since the new standard allowed the peripheral to send large amounts of data back to the host, devices that had previously used SCSI interfaces could be produced at a much lower cost. In the printer venue, this allows for faster printing and back-channel status and management. The IEEE 1284 standard allows for faster throughput and bidirectional data flow with a theoretical maximum throughput of 4 megabytes per second actual throughput is around 2 megabytes/second depending on hardware.
1284 included all of these modes, and allowed operation in any of them.Īn IEEE 1284 compliant printer cable, with both DB-25 and 36-pin Centronics connectors In March 1994, the IEEE 1284 specification was released. In 1991 the Network Printing Alliance was formed to develop a new standard. This proved adaptable, and led to the "Enhanced Parallel Port" standard, which worked like Bi-Directional mode but greatly increased the signalling speeds to 2 MByte/s, and later the "Extended Capability Port" version increased this to 2.5 MByte/s. This used the status pins of the original port to form a 4-bit parallel port for sending arbitrary data back to the host.Ī further modification, "Bi-Directional", used the status pins to indicate the direction of data flow on the 8-bit main data bus by indicating there was data to send to the host on one of the pins, all eight data pins became available for use. This led to an early expansion of the system introduced by HP, the "Bitronics" implementation released in 1992. This was a serious limitation as printers became "smarter" and a richer set of status codes were desired. Separate pins in the port allow status information to be sent back to the computer. The original port design was send-only, allowing data to be sent from the host computer to the printer. As printers grew in sophistication, and the cost of memory dropped, printers began adding increasing amounts of buffer memory, initially a line or two, but then whole pages and then documents. The complexity of printing a character as a sequence of columns of dots is managed by the printer electronics, which receives character encodings from the computer one at a time, with the bits transferred serially or in parallel. Character sets on early printers normally used 7 by 5 "pixels" to produce 80-column text. The entire print head is moved horizontally in order to print a line of text, striking the paper several times to produce a matrix for each character. Each pin is attached to some sort of actuator, a solenoid in the case of Centronics, which can pull the pin forward to strike a ribbon and the paper.
#What is ieee 1284 controller series#
Centronics had introduced the first successful low-cost seven-wire print head, which used a series of solenoids to pull the individual metal pins to strike a ribbon and the paper.Ī dot matrix print head consists of a series of metal pins arranged in a vertical row. In the 1970s, Centronics developed the now-familiar printer parallel port that soon became a de facto standard. An IEEE 1284 36-pin female on a circuitboard