COM (hardware interface)

COM (hardware interface)

COM is the original, yet still common, name of the serial port interface on IBM PC-compatible computers. It might not only refer to physical ports, but also to virtual ports, such as ports created by bluetooth or USB-to-Serial adapters.

Most PC-compatible systems in the 1980s and 1990s had one or two ports, with communication interfaces defined like this:

*COM1: I/O port 0x3F8, IRQ 4
*COM2: I/O port 0x2F8, IRQ 3
*COM3: I/O port 0x3E8, IRQ 4
*COM4: I/O port 0x2E8, IRQ 3

As of 2007, most systems ship with one or no physical COM ports.

I/O addresses

The COM ports are interfaced by an integrated circuit such as 16550 UART. This IC has seven internal 8-bit registers which hold information and configuration data about which data is to be sent or was received, the baud rate, interrupt configuration and more. In the case of COM1, these registers can be accessed by writing to or reading from the I/O addresses 0x3F8 to 0x3FF.

If the CPU, for example, wants to send information out on COM1, it writes to I/O port 0x3F8, as this I/O port is "connected" to the UART IC register which holds the information that is to be sent out.

ee also

*Device file
*LPT
*Input/Output Base Address


Wikimedia Foundation. 2010.

Игры ⚽ Поможем решить контрольную работу

Look at other dictionaries:

  • Com — Contents 1 Academia 2 Business, politics and culture 3 Computing 4 …   Wikipedia

  • Interface (computing) — For other uses, see Interface. In the field of computer science, an interface is a tool and concept that refers to a point of interaction between components, and is applicable at the level of both hardware and software. This allows a component,… …   Wikipedia

  • Interface — Die Schnittstelle oder das Interface [ˈɪntɚfeɪs] (englisch „Grenzfläche“) ist der Teil eines Systems, der der Kommunikation dient. Der Begriff stammt ursprünglich aus der Naturwissenschaft und bezeichnet die physikalische Phasengrenze zweier… …   Deutsch Wikipedia

  • Hardware-in-the-loop simulation — Hardware in the loop (HIL) simulation is a technique that is used in the development and test of complex real time embedded systems. HIL simulation provides an effective platform by adding the complexity of the plant under control to the test… …   Wikipedia

  • Com One group — Type Public Industry Computer Networks Founded 1987 Headquarters Cestas, Gironde, France Key people Jacques Saubade, Pres …   Wikipedia

  • interface — The way in which separate computer systems or computer programs interact with each other, or the way in which a computer user interacts with computer software or hardware. Practical Law Dictionary. Glossary of UK, US and international legal terms …   Law dictionary

  • Hardware description language — In electronics, a hardware description language or HDL is any language from a class of computer languages and/or programming languages for formal description of electronic circuits. It can describe the circuit s operation, its design and… …   Wikipedia

  • COM+ — Das Component Object Model [kəmˈpoʊnənt ˈɒbdʒɪkt ˈmɒdl] (Abk. COM) ist eine von Microsoft entwickelte Plattform Technologie, um unter dem Betriebssystem Windows Interprozesskommunikation und dynamische Objekterzeugung zu ermöglichen. COM fähige… …   Deutsch Wikipedia

  • Hardware-assisted virtualization — In computing, hardware assisted virtualization is a platform virtualization approach that enables efficient full virtualization using help from hardware capabilities, primarily from the host processors. Full virtualization is used to simulate a… …   Wikipedia

  • Hardware Compatibility List — Ein Betriebssystem ist die Software, die die Verwendung (den Betrieb) eines Computers ermöglicht. Es verwaltet Betriebsmittel wie Speicher, Ein und Ausgabegeräte und steuert die Ausführung von Programmen. Betriebssystem heißt auf Englisch… …   Deutsch Wikipedia

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”