| 摘要 |
PURPOSE:To shorten the time required for data communication by coupling plural slave stations in serial and changing received data as required and transmitting this data to the following slave station. CONSTITUTION:Data transmitted from a master station 1 is partially fetched into the first slave station 2 or information of the station 2 is added to this data is transferred to the second slave station 3. Data is transferred to the host station 1 while being changed successively by individual slave stations similarly, and the normal termination or the occurrence of abnormality on some communication line is detected in accordance with the received final result. Data frames used in this data communication are constituted based on high level data control procedures (HDLC), and the flag sequence at the beginning and the end is an 8-bit control field of '01111110', and a data length field has, for example, 8 bits. Data fields have a variable length and are objective information transmitted and received between the master station and slave stations, and a frame check sequence is the bit sequence which discriminates whether the data frame is correct or not.
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