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It was an industry de facto standard for many years, and was finally standardized as IEEE 1284 in the late 1990s, which defined the Enhanced Parallel Port (EPP) and Extended Capability Port (ECP) bi-directional versions. Today, the parallel port interface is virtually non-existent in new computers because of the rise of Universal Serial Bus ...
An IEEE 1284 36-pin female on a circuit board. In the 1970s, Centronics developed the now-familiar printer parallel port that soon became a de facto standard.Centronics had introduced the first successful low-cost seven-wire print head [citation needed], which used a series of solenoids to pull the individual metal pins to strike a ribbon and the paper.
Parallel versus serial communication In data transmission , parallel communication is a method of conveying multiple binary digits ( bits ) simultaneously using multiple conductors. This contrasts with serial communication , which conveys only a single bit at a time; this distinction is one way of characterizing a communications link .
The CIA had two 8-bit bidirectional parallel I/O ports. Each port had a corresponding Data Direction Register, which allowed each data line to be individually set to input or output mode. A read of these ports always returned the status of the individual lines, regardless of the data direction that had been set.
Asynchronous start-stop is the lower data-link layer used to connect computers to modems for many dial-up Internet access applications, using a second (encapsulating) data link framing protocol such as PPP to create packets made up out of asynchronous serial characters. The most common physical layer interface used is RS-232D.
For example, a USB-to-parallel-port converter might work well with a printer, but not with a scanner that requires bidirectional use of the data pins. For a product developer, using USB requires the implementation of a complex protocol and implies an "intelligent" controller in the peripheral device.
For example, on the original IBM PC, a male D-sub was an RS-232-C DTE port (with a non-standard current loop interface on reserved pins), but the female D-sub connector on the same PC model was used for the parallel "Centronics" printer port. Some personal computers put non-standard voltages or signals on some pins of their serial ports.
A parallel slave port (PSP) is an interface found on some PIC microcontrollers. [1] It allows 8-bit asynchronous bidirectional data transfer between the PIC and external devices, such as other microcontrollers or personal computers. [2]