IBM Keyboard
・OADG テクニカルリファレンス DOSV ・OADG 109キーボード ・PS/2 SCANCODE and USB usage ・USB HID to PS/2 Scan Code Translation Table 5.2. XT Keyboard The original, or "XT", keyboard uses a single byte to report a key press and the same byte, but with the high bit set, to report a key release. It has no "output" capability - no indicator LEDs. 5.3. AT Keyboard The AT keyboard uses a single byte to report a key press and two bytes, an F0 followed by the original byte, to report a key release. It adds three indicator lights (Num Lock, Caps Lock, and Scroll Lock) which can be turned on and off under software control. The scan code set used is different from that used by the XT keyboard. 5.4. PS/2 Keyboard The PS/2 keyboard is programmably selectable to emulate an XT keyboard, an AT keyboard, or still another set of scan codes that tries to simplify the confusion caused by efforts to extend the keyboard with additional keys and still maintain backwards compatibility. In all but this latter mode, many keys generate streams of "virtual" key presses to simulate appropriate keystrokes on the older keyboards. On power-on, the keyboard defaults to emulating the AT keyboard. [3] Technical Reference, IBM Personal Computer [4] Technical Reference, Personal Computer AT IBM [5] Personal System/2 Model 80 Technical Reference IBM 4. Definition of Terms AT keyboard A keyboard presenting the interface defined in section 4 of [4], excluding the electrical specifications therein. engravings The glyphs marked on the keys. What the user thinks the keys mean. PS/2 keyboard A keyboard presenting the interface defined in section 6 of [5], excluding the electrical and BIOS specifications therein. scan code A positional code for a particular key, not necessarily related to the engraving on that key. In other words, the leftmost key on the top row of the main alphabetic pad is represented by the same scan code regardless of whether it has a Q printed on it, as on a US keyboard, or an A printed on it, as on a French keyboard. XT keyboard A keyboard presenting the interface defined in section ?? of [3], excluding the electrical specifications therein.