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In computing, a serial port is an interface on a computer system with which information is transferred in or out one bit at a time (contrast parallel port). Throughout most of the history of personal computers, this was accomplished using the RS-232 standard over simple cables connecting the computer to a device such as a terminal or modem.
Mice, keyboards, and other devices were also oftenconnected this way.
While RS-232 originally specified a 25-pin D-type connector, these were large and awkward, and most of the pins were unused (after all, since data is sent one bit at a time, only one wire is needed for data in each direction plus a few control signals), so it was common to use other connectors for these ports (in particular the DB-9 version used by the original IBM PC). In Europe, the related RS-422 standard was popular, and often used German DIN connectors.
In very recent years, more advanced electronics has made possible more reliable and higher-speed serial communications, so RS-232 is being supplanted by newer standards such as USB and Firewire. These make it possible to connect devices that would not have been feasible over slower serial connections, such as storage devices and sound and video devices.
In LinuxThis article is about Linux-based operating systems, GNU/Linux, and related topics. See Linux kernel for the kernel itself. See Linux (washing powder) for the Swiss brand of washing powder. Tux, a plump penguin, is the official Linux mascot Linux is the n, the serial port devices are usually called /dev/ttyS* where * is a number starting with 0.
Traditionally IBM PC systems have allocated their first four serial ports according to the configuration in the table below.
| PORT NAME | InterruptIn computer engineering, an interrupt is a signal from a device which typically results in a context switch: that is, the processor sets aside what it's doing and does something else. Digital computers usually provide a way to start software routines in r # | Starting I/OOn a computer system, an I/O address is specific portion of address space in the CPU used to read/write to specific devices within the computer. See Also Input/Output. | Ending I/OOn a computer system, an I/O address is specific portion of address space in the CPU used to read/write to specific devices within the computer. See Also Input/Output. |
|---|---|---|---|
COM1 | IRQIRQ stands for i''nterrupt r''e''q''uest . IRQs are used by peripherals as a way to bring the processor into attention. In the early PC-architecture the chips 8259A and 8259B takes care of the requests and sends them to the processor in form of ordinary s 4 | 0x3f8 | 0x3ff
|
COM2 | IRQIRQ stands for i''nterrupt r''e''q''uest . IRQs are used by peripherals as a way to bring the processor into attention. In the early PC-architecture the chips 8259A and 8259B takes care of the requests and sends them to the processor in form of ordinary s 3 | 0x2f8 | 0x2ff
|
COM3 | IRQIRQ stands for i''nterrupt r''e''q''uest . IRQs are used by peripherals as a way to bring the processor into attention. In the early PC-architecture the chips 8259A and 8259B takes care of the requests and sends them to the processor in form of ordinary s 4 | 0x3e8 | 0x3ef
|
COM4 | IRQ 3 | 0x2e8 | 0x2ef
|
See also: parallel port.