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1. 发明授权

US4712214A Protocol for handling transmission errors over asynchronous communication lines 失效
标题翻译：通过异步通信线路处理传输错误的协议
公开(公告)号：US4712214A
公开(公告)日：1987-12-08
申请号：US817699
申请日：1986-01-10
申请人： Clifford B. Meltzer , Krishnamurthi Kannan , Thomas G. Burket , Deborah J. Kruesi , Gordon W. Braudaway
发明人： Clifford B. Meltzer , Krishnamurthi Kannan , Thomas G. Burket , Deborah J. Kruesi , Gordon W. Braudaway
IPC分类号： H04N7/173 , H04L1/00 , H04L1/16 , H04L29/08 , G06F11/10 , G08C25/00
CPC分类号： H04L1/0083
摘要： 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 number of data bytes in the packet; one byte operating as a control character indicating the functional nature of the packet; data bytes; and, two checksum bytes which precede the last ETX byte. Among the advantages of transmissions using packets containing the foregoing improved combination of bytes, is the fact that all transmission errors will be detected and upon detection of an error in a packet, the transmitter is immediately notified and retransmission is carried out only from the erroneous packet rather than from the beginning of the entire sequence as in the prior art.
摘要翻译：公开了一种用于在具有完全透明度的数据链路级别的异步通信模式下自动检测和恢复传输错误的系统或方案，其中传输是数据分组序列的形式，并且改进的组合每个数据包中使用文本结尾（ETX）字节以及校验和来检测错误。在组合数据包的数据之后，ETX字符是为每个数据包动态选择的。该字符与其各自的分组中的剩余字符代码不同，并且使其成为文本开头字节（STX）之后的第二个字节。每个数据包中的第三个字节是前一个ETX字节的补码，后一个字节也是数据包中的最后一个字节。因此，每个分组中的第二个和最后一个字节是相同的，并且与所有其他字节不同，第三个字节是它们的补码。每个分组中的其他字节包括：指示给定传输序列中的分组中的分组的位置的一个字节; 将分组的集合与其他传输序列区分开的字节; 两个字节表示数据包中的数据字节数; 一个字节作为指示分组的功能性质的控制字符操作; 数据字节; 以及在最后一个ETX字节之前的两个校验和字节。在使用包含上述改进的字节组合的分组的传输的优点之中，是所有的传输错误将被检测到，并且在检测到分组中的错误之后，发送器立即被通知，并且仅从错误的分组而不是像现有技术那样从整个序列开始。

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