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Method to Provide a Keyboard for a Battery-Operated Environment

IP.com Disclosure Number: IPCOM000038525D
Original Publication Date: 1987-Jan-01
Included in the Prior Art Database: 2005-Jan-31
Document File: 1 page(s) / 13K

Publishing Venue

IBM

Related People

Davenport, CS: AUTHOR [+2]

Abstract

A method is described for taking the intelligence out of the keyboard and placing it within a system unit, thus reducing the size of the keyboard and eliminating a requirement for having power applied to the keyboard. This keyboard adapter operates asynchronously and requires no system clocks for the keyboard. The following functions are provided: key detection, debounce/ noise elimination, and typamatic. A reset function is decoded to provide a system reset for the key combination of FN-CTRL-DEL. The keyboard interface operates on a program routine referred to as NMI. The scan code translations are done in software. There is a register for compatibility to other models of personal computers, located at Port 60 so that the NMI routine can store the translated scan code and send them to the Basic I/O System (BIOS) routine.

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Method to Provide a Keyboard for a Battery-Operated Environment

A method is described for taking the intelligence out of the keyboard and placing it within a system unit, thus reducing the size of the keyboard and eliminating a requirement for having power applied to the keyboard. This keyboard adapter operates asynchronously and requires no system clocks for the keyboard. The following functions are provided: key detection, debounce/ noise elimination, and typamatic. A reset function is decoded to provide a system reset for the key combination of FN-CTRL-DEL. The keyboard interface operates on a program routine referred to as NMI. The scan code translations are done in software. There is a register for compatibility to other models of personal computers, located at Port 60 so that the NMI routine can store the translated scan code and send them to the Basic I/O System (BIOS) routine. The scan code register is located at Port 7D which is used to read the scan code or write a scan code in diagnostic mode. Port 7C uses the three high-order bits to enable the keyboard NMI and place the adapter in diagnostic mode during a write operation. A read of Port 7C indicates also if a keyboard is attached. There is a flip-flop for each key which is set to the non-depressed state at power-on. The keyboard is scanned until a change in a key state is detected, at which time the scanning is stopped and the 5-milliseconds (msec) counter is set. At the end of 5 msec, if the change is still there, it is deemed valid and the flip-flop is loaded to the new state. The scan code register is loaded, and an NMI is presented to the processor. The scanning will resume once the scan code register is read which also clears the...