Protocol for handling transmission errors over asynchronous communication lines
US4712214A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jan 10, 1986 |
| Grant date | Dec 8, 1987 |
| Priority date | — |
| Expiry date | Jan 10, 2006 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L1/0083
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
A system or scheme for automatic detection of and recovery from transmission errors in the asynchronous communication mode at the data link level with complete transparency at the higher levels is disclosed wherein the transmissions are in the form of a sequence of data packets, and an improved combination of end-of-text (ETX) bytes along with checksums is used in each data packet to detect errors. The ETX character is dynamically selected for each packet after the data comprising the packet has been assembled. This character is coded differently from the remaining character codes in its respective packet and is made the second byte thereof following the start-of-text byte (STX). The third byte in each packet is made the complement of the preceding ETX byte, the latter of which is also made the last byte in the packet. Thus, the second and last bytes in each packet are identical, and different from all the other bytes, and the third byte is their complement. Other bytes in each packet include: one byte indicating the location of the packet in a set in a given transmission sequence; a byte distinguishing the packet's set from other transmission sequences; two bytes indicative of the…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.