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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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本文主要介紹了數(shù)據(jù)服務(wù)器的硬件系統(tǒng)設(shè)計及軟件系統(tǒng)設(shè)計。本數(shù)據(jù)服務(wù)器是上位機與現(xiàn)場儀表進行數(shù)據(jù)交換的橋梁 ,上下都采用RS4 85接口。數(shù)據(jù)服務(wù)器通過人為設(shè)定的采樣周期對現(xiàn)場儀表進行采樣 ,讀回數(shù)據(jù)并以一定的格式進行存儲。數(shù)據(jù)服務(wù)器根據(jù)上位機發(fā)來的命令進行相應(yīng)的操作 ,并返回數(shù)據(jù)給上位機 ,包括讀取當(dāng)前時間、所連儀表起始地址、單臺或全部儀表的當(dāng)前數(shù)據(jù)、歷史數(shù)據(jù)。