Bi-directional keyboard interface circuit
US4875043A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 8, 1988 |
| Grant date | Oct 17, 1989 |
| Priority date | — |
| Expiry date | Feb 8, 2008 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03M11/20
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
The present invention includes a keyboard encoder which encodes a key selected by an operator. The encoder is isolated from a bi-directional bus by an isolation circuit. When a key has been selected a key code is made available for reading by a separate CPU. The separate CPU enables transfer of the key code from the encoder to the bi-directional bus and then reads the key code. The separate CPU acknowledges receipt of the key code and provides feedback to keyboard operator by sending a bank and light selection code to the keyboard over the bi-directional interface bus, after the isolation circuit has been reactivated and after a function, to be performed by the separate CPU and specified by the key code, has been started. The isolation circuit prevents the key code and the bank and light selection code from becoming intermixed on the bi-directional bus. The bank select code is used to select a bank of light code decoders which activate a light corresponding to the light code. The light activated stays lit until another key is selected. The transmission of a second bank and light selection code after a single key is selected can be used to activate an additional light associated wit…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.