|Superseded by||PS/2 connector Universal Serial Bus|
|Connector||Male at the keyboard side, DIN connector|
|Data signal||Serial data at 10 to 16 kHz with 1 stop bit, 1 start bit, 1 parity bit (odd)|
|Female (at the computer side, viewed from front)|
|Pin 1||CLK||Clock signal|
|Pin 3||N/C||Not connected. Reset on older keyboards|
|Pin 5||VCC||+5V DC|
The IBM AT keyboard or Model F keyboard was a keyboard with 84 keys introduced with the IBM PC/AT computer. It succeeded the 83-key PC/XT keyboard and therefore did not have many of the features seen on modern keyboards such as inverted-T arrow keys and dual ctrl and alt keys. It was later replaced with the 101-key Enhanced keyboard. Nonetheless, "AT keyboard" remains a popular name for any keyboard that uses the five-pin DIN connector. This connector is often considered a Legacy port. Many Enhanced keyboards used this, though it was eventually superseded by the PS/2 connector, which is mechanically different but electrically and protocol-wise identical; thus, the AT keyboard protocol remained the most common standard on PC keyboards well into the 2000s. Many modern computers now use Universal Serial Bus (USB) connectors instead of, or in addition to, PS/2 connectors. The USB connector is electrically and protocol-wise quite different.
Compared to the 83-key XT keyboard, the AT keyboard uses a different communication protocol and a different set of scancodes. Despite having the same connector, the two are not interchangeable. Some PC-compatible mid-to-late 1980s keyboards not made by IBM were switchable between the two protocols and scancode sets, usually with a slider type switch on the underside.
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