Keypad scanner
US5621402A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jul 21, 1993 |
| Grant date | Apr 15, 1997 |
| Priority date | — |
| Expiry date | Jul 21, 2013 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03M11/20
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A keypad scanner for a keypad having a plurality of keys which may be pressed into a down state includes circuitry for detecting when no or any key is pressed down and thereupon generating a no or any key down signal, circuitry for detecting when more than one key is pressed down and thereupon generating a multiple key down signal, and an interrupt generator coupled to the aforementioned circuitry. The interrupt generator itself includes circuitry for detecting a change in no or any key down signal level, circuitry for detecting a change in multiple key down signal level, and circuitry for generating an interrupt signal when either the circuitry for detecting a change in no or any key down signal level or the circuitry for detecting a change in multiple key down signal level detects a change.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.