描述
信息保護(hù)和恢復(fù):當(dāng)偶發(fā)性故障條件出現(xiàn)時(shí),不破壞plc內(nèi)部的信息,一旦故障條件消失,就可以恢復(fù)正常繼續(xù)原來(lái)的工作。所以,plc在檢測(cè)故障條件時(shí),立即把現(xiàn)狀態(tài)存入存儲(chǔ)器,軟件配合對(duì)存儲(chǔ)器進(jìn)行封閉,禁止對(duì)存儲(chǔ)器的任何操作,以防存儲(chǔ)器信息被沖掉,一旦檢測(cè)到外界環(huán)境正常后,便可恢復(fù)到故障發(fā)生前的狀態(tài),繼續(xù)原來(lái)的程序工作。
設(shè)置警戒時(shí)鐘wdt:機(jī)械設(shè)備的動(dòng)作時(shí)間一般是不變的,可以以這些時(shí)間為參考,當(dāng)plc發(fā)出控制信號(hào),相應(yīng)的執(zhí)行機(jī)械動(dòng)作,同時(shí)啟動(dòng)一個(gè)定時(shí)器,定時(shí)器的設(shè)定值比正常情況下機(jī)械設(shè)備的動(dòng)作時(shí)間長(zhǎng)20%,若時(shí)間到,plc還沒(méi)有收到執(zhí)行機(jī)構(gòu)動(dòng)作結(jié)束信號(hào),則啟動(dòng)報(bào)警。
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