中斷的內(nèi)容有很多種，比如外部中斷、通信中的發(fā)送和接受中斷、定時(shí)和計(jì)數(shù)的時(shí)鐘中斷、還有WDT復(fù)位中斷等，它們豐富了在處理各種事務(wù)時(shí)響應(yīng)種類。這樣講也許你并不能完全理解中斷的內(nèi)部結(jié)構(gòu)和操作順序，我們做一個(gè)小小的例子來說明.
每一個(gè)設(shè)備總是不會(huì)忘記有一個(gè)按鈕，它也是在我們遇到緊急情況時(shí)使用的，那就是急停按鈕。當(dāng)我們遇到人身事故和意外情況時(shí)我們只要按下它，機(jī)器立即停止所有的操作，并等待處理完意外后再恢復(fù)操作。急停按鈕連接PLC內(nèi)部的內(nèi)部I/O接口上，當(dāng)按鈕給一個(gè)外部觸發(fā)信號(hào)時(shí)，對(duì)I/O進(jìn)行再次檢測(cè)，當(dāng)確認(rèn)有外部觸發(fā)信號(hào)時(shí)，保護(hù)現(xiàn)場(chǎng)并將程序計(jì)數(shù)器自動(dòng)轉(zhuǎn)到相應(yīng)的外部I/O中斷程序中去，當(dāng)外部中斷程序處理完畢，程序計(jì)數(shù)器返回到主程序繼續(xù)工作。有一點(diǎn)可以說明的是我們一般會(huì)把急停按鈕的外部中斷升至別，從而保證。
當(dāng)我們?cè)诠ぷ魍暌粋€(gè)工件時(shí)，給PLC一個(gè)信號(hào)，將PLC的內(nèi)部計(jì)數(shù)器加1來計(jì)算我們的工作量時(shí)，一個(gè)簡(jiǎn)單的計(jì)數(shù)器能解決問題，當(dāng)然它們也能夠在掉電的情況下保持?jǐn)?shù)據(jù)，促使數(shù)據(jù)不丟失，這也是我們所渴望的。
PLC還具有計(jì)數(shù)器的功能，當(dāng)我們?cè)诮邮芤恍└咚俚臄?shù)據(jù)時(shí)，這里所說的高速是在在微秒級(jí)的數(shù)據(jù)，比如條碼掃描機(jī)在不斷的掃描數(shù)據(jù)，數(shù)據(jù)處理器DSP計(jì)算的高速信號(hào)等，我們就要采用到計(jì)數(shù)器來幫助我們進(jìn)行計(jì)數(shù)。它在PLC執(zhí)行程序時(shí)一旦發(fā)現(xiàn)計(jì)數(shù)器對(duì)應(yīng)的中斷，就會(huì)立即放下手上的工作。經(jīng)過再次編程的梯形圖程序說明我們?cè)趫?zhí)行程序時(shí)計(jì)數(shù)器會(huì)自動(dòng)的執(zhí)行對(duì)應(yīng)的工作，從而將計(jì)數(shù)器的級(jí)別升至高一級(jí)別。
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