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The PC 97 standard requires that a computer's BIOS must detect and work with USB HID class keyboards that are designed to be used during the boot process. Some keyboards implement the USB Boot Keyboard profile specified in the USB Device Class Definition for Human Interface Devices (HID) v1.11 and are explicitly configured to use the boot protocol.
The HID standard was adopted primarily to enable innovation in PC input devices and to simplify the process of installing such devices. Prior to the introduction of the HID concept, devices usually conformed to strictly defined protocols for mouse, keyboards and joysticks; for example, the standard mouse protocol at the time supported relative X- and Y-axis data and binary input for up to two ...
The USB HID keyboard interface requires that it explicitly handle key rollover, with the full HID keyboard class supporting n-key rollover. However, the USB boot keyboard class (designed to allow the BIOS to easily provide a keyboard in the absence of OS USB HID support) only allows 6-key rollover.
The (mandatory) HID report protocol, which is what operating systems use, imposes no restrictions and supports full n-key rollover. The HID specification however imposes no requirements on rollover and low-end keyboards may impose the same restrictions regardless of whether the boot protocol or the HID report protocol is used.
The written USB 3.0 specification was released by Intel and its partners in August 2008. The first USB 3.0 controller chips were sampled by NEC in May 2009, [4] and the first products using the USB 3.0 specification arrived in January 2010. [5] USB 3.0 connectors are generally backward compatible, but include new wiring and full-duplex operation.
Bluetooth HID is a lightweight wrapper of the human interface device protocol defined for USB. The use of the HID protocol simplifies host implementation (when supported by host operating systems) by re-use of some of the existing support for USB HID in order to support also Bluetooth HID. Keyboard and keypads must be secure.
The keyboard sends the key code to the keyboard driver running in the main computer; if the main computer is operating, it commands the light to turn on. All the other indicator lights work in a similar way. The keyboard driver also tracks the shift, alt and control state of the keyboard.
USB keyboards, mice, and I/O devices are the most common devices connected to a KVM switch. The classes of KVM switches discussed below are based on different types of core technologies, which vary in how the KVM switch handles USB I/O devices—including keyboards, mice, touchscreen displays, etc. (USB-HID = USB Human Interface Device)