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Marker Code Method for Keyboard Scan Codes

IP.com Disclosure Number: IPCOM000039729D
Original Publication Date: 1987-Jul-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Voorhees, R: AUTHOR

Abstract

This article describes the use of special marker code signals for distinguishing new keys on the Ferrari keyboard to application software written specifically for that keyboard while retaining compatibility for software written for previous keyboards. The marker codes are ignored by the latter software. The personal computer (PC) keyboard uses scan codes to tell the system which keys have been pressed and released. When a key is pressed, a code is sent to the system representing that key, and when released, another code is sent, representing the release of that key. An example is shown in Fig. 1. The up-arrow/numeral-8 key is the only key on the keyboard with that particular function, so when its scan code is received, the system knows exactly how to translate it. A single scan code is all that is necessary.

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Marker Code Method for Keyboard Scan Codes

This article describes the use of special marker code signals for distinguishing new keys on the Ferrari keyboard to application software written specifically for that keyboard while retaining compatibility for software written for previous keyboards. The marker codes are ignored by the latter software. The personal computer (PC) keyboard uses scan codes to tell the system which keys have been pressed and released. When a key is pressed, a code is sent to the system representing that key, and when released, another code is sent, representing the release of that key. An example is shown in Fig. 1. The up-arrow/numeral-8 key is the only key on the keyboard with that particular function, so when its scan code is received, the system knows exactly how to translate it. A single scan code is all that is necessary. The Ferrari keyboard was designed with extra keys. The problem that occurred was how to make the extra keys work with existing programs, while also making them unique so that new software could use them to the full extent. An example of an existing key and an extra, similar key is shown in Fig. 2.

(Image Omitted)

Both keys perform the up-arrow function. In order that old software still recognizes the up-arrow function on the new key, that key is given the same scan code as the existing key with the up-arrow/8 function. The keyboard automatically adjusts the shift states presented to the system so that the up- arrow key never produces the numeral "8". This allows the old software to work. However,...