Flash NRZI infrared modem
US5602873A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Oct 14, 1994 |
| Grant date | Feb 11, 1997 |
| Priority date | — |
| Expiry date | Oct 14, 2014 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L25/49
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
A modulation scheme and system, compatible with both the asynchronous IRDA mode and the synchronous mode of IR communication, involves Non-Return-to-Zero-Inverted (NRZI) and Flash pulse encoding in conjunction with zero-bit stuffing. A digital data stream has a zero-bit inserted therein, before NRZI format encoding, whenever five consecutive one's are detected in the stream to enable the controller to distinguish the data from flags, which are exempt from the zero-bit insertion, and to provide enough transitions in the data so that the demodulator's digital phase lock loop can stay locked independent of the data contents. A Flash pulse (of from 3/16 to 8/16 of bit cell width, depending on the data rate) is generated whenever a transition is detected in the NRZI formatted data. The result, in keeping with IRDA modulation, is that a Flash pulse is generated whenever a zero occurs in the data stream. On the demodulation side, whenever a Flash pulse is received, the level of the receive line is toggled resulting in an output in NRZI format. Using this modulation scheme with a serial controller which supports NRZI and bit-stuffing, a system may be constructed that uses the controller's …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.