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Introduction to RS485 RS232 , RS422 , RS423 and RS485 are serial communication methods for computers and devices. RS232 is without doubt the best known interface, because this serial interface is implemented on almost all computers available today. But some of the other interfaces are certainly interesting because they can be used in situations where RS232 is not appropriate. We will conce
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針對現有煤礦安全監(jiān)控系統(tǒng)的RS485總線采用主控機對子通信節(jié)點輪詢呼叫方式存在實時性差、無法實現即插即用功能、通信效率低的問題,設計了一種基于類令牌環(huán)的RS485多主通信協(xié)議模塊。令牌信息包含在每個數據幀的幀頭,RS485總線空閑4byte時間內為幀結束標志,RS485總線空閑4~5byte時間內為關鍵設備搶發(fā)時間,RS485總線空閑5~6byte時間段為一般設備搶發(fā)時間;正常情況下通信節(jié)點按令牌順序輪流與主控機交互數據,當設備有緊急情況需要搶先上傳數據時,可在搶發(fā)時間內搶占RS485總線。測試分析表明,在RS485總線容量不大且信道干擾較小的情況下,該模塊具有良好的使用效果。