Keyboard controller (computing)

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For other uses, see Keyboard controller.
Keyboard controller and AT-Keyboard jack on an AT-Mainboard

In computing, a keyboard controller is a device that interfaces a keyboard to a computer. Its main function is to inform the computer when a key is pressed or released. When data from the keyboard arrives, the controller raises an interrupt (a keyboard interrupt) to allow the CPU to handle the input.

If a keyboard is a separate peripheral system unit (such as in most modern desktop computers), the keyboard controller is not directly attached to the keys, but receives scancodes from a microcontroller embedded in the keyboard via some kind of serial interface. In this case, the controller usually also controls the keyboard's LEDs by sending data back to keyboard through the wire.

The IBM PC AT used an Intel 8042 chip to interface to the keyboard. In computers with PS/2 connectors the keyboard controller also includes a mouse controller. Today the keyboard controller is a unit inside a Super I/O device or replaced by USB-Keyboard as Human interface device.

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