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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.
The Parallel Line Internet Protocol (PLIP) is a computer networking protocol for direct computer-to-computer communications using the parallel port, normally used for connections to a printer. [ 1 ] [ 2 ]
However, parallel lines have lower latency than serial lines, this makes parallel lines is still used on memory bus like DDR SDRAM. Cable length or link length: Crosstalk creates interference between the parallel lines, and the effect worsens with the length of the communication link. This places an upper limit on the length of a parallel data ...
In general, parallel interfaces are quoted in B/s and serial in bit/s. The more commonly used is shown below in bold type. On devices like modems , bytes may be more than 8 bits long because they may be individually padded out with additional start and stop bits; the figures below will reflect this.
The simplest system bus has completely separate input data lines, output data lines, and address lines. To reduce cost, most microcomputers have a bidirectional data bus, re-using the same wires for input and output at different times. [20] Some processors use a dedicated wire for each bit of the address bus, data bus, and the control bus.
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.
The 8255 provides 24 I/O pins with four programmable direction bits: one for Port A(7:0) (i.e., all pins in the port), one for Port B(7:0), one for Port C(3:0) and one for Port C(7:4). By contrast, the Motorola and MOS chips provide only 16 I/O pins plus 4 control pins, but the Motorola/MOS chips allow the direction (input or output) of all I/O ...