| 摘要 |
PROBLEM TO BE SOLVED: To reduce occurrence of collision of communication in a data communication unit adopting a half-duplex communication system. SOLUTION: The data communication unit confirms whether or not communication collision has taken place, when transmitting a polling packet, calculates frequency of collisions on the occurrence of communication collision and confirms whether or not the calculation result exceeds a preset threshold value (steps 100 to 106). When the calculation result exceeds the threshold, the data communication unit receives a message packet causing the communication collision, determines whether or not the message has high real time performance, and changes the setting of polling intervals, when the message has high real time performance (steps 108 to 112). After that, the data communication unit informs a slave station about the setting polling interval and transmits polling packets at the setting polling interval (step 114).
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