【正文】 這種通訊也可被用來(lái)連接特殊功能的芯片和幾個(gè)微型機(jī)。這些線很容易和二進(jìn)制的設(shè)備相連接使用，如開(kāi)關(guān)，恒溫器，固態(tài)繼電器，閥門(mén)，電機(jī)等。存儲(chǔ)依據(jù)設(shè)備的大小不同而類(lèi)型有所不同，但作為處理器具有相同的特征寬度（4,8,16 比特等）。這一發(fā)展過(guò)程可能涉及仿真,使用硬件仿真功能以及強(qiáng)大的軟件工具使用先進(jìn)的開(kāi)發(fā)系統(tǒng)。s not supported.Universal I/OWhile there are concerns about the lack of patible munications between PLCs from different vendors, the connection at the other endthe I/Ois even more fragmented .With rare exceptions, I/O is still proprietary .Yet there are those who feel that I/O will eventually bee more universal .GE Fanuc is hoping to do that with its Genius smart I/O line. The independent I/O makers are pulling in the same direction. Many say that I/O is such a highvalue item that PLC makers will always want to keep it proprietary .As Ken Jannotta, says: The I/O is going to be a disproportionate amount of the hardware sale. Certainly each PLC vendor is going to try to protect that. For that reason, he says, PLC makers won39。ve heard a lot about MAP in the last few years ,and a lot of panies have jumped on the bandwagon. Many, however, were disappointed when a fullydefined and pleted MAP specification didn39。s very difficult to write a trigonometric function using ladder logic. Languages gaining acceptance include Boolean, control system flowcharting, and such function chart languages as Graphcet and its variation .And there39。 there can still be a significant saving in I/O and other chips pared to a conventional microprocessor based circuit. More exact replacement for ROM devices can be obtained in the form of variants with 39。 general manager, Siemens Energy amp。re appropriate. one, he says, is where the size of the process control system that39。t yet talk to MAP.Since it39。圖A1 哈弗結(jié)構(gòu)圖A2 傳統(tǒng)的普林斯頓結(jié)構(gòu)只讀存貯器(ROM) ROM是通常的永久性的，非應(yīng)用程序的易失性存儲(chǔ)器。這些器件價(jià)格當(dāng)然比同等ROM設(shè)備貴，但沒(méi)有完整的等效電路。微電腦和微控制器的許多應(yīng)用涉及到二進(jìn)制編碼的十進(jìn)制數(shù)據(jù)處理（BCD）（數(shù)字顯示為例）。一些設(shè)備允許一個(gè)I/O端口和其他組件作為系統(tǒng)總線配置來(lái)擴(kuò)展片外存儲(chǔ)器和I/O口。定時(shí)/計(jì)數(shù)器設(shè)施許多應(yīng)用的單片機(jī)需要對(duì)過(guò)去的真實(shí)時(shí)間準(zhǔn)確的評(píng)價(jià)。這個(gè)設(shè)備通常有一個(gè)特殊的輸入引腳，可直接驅(qū)動(dòng)計(jì)數(shù)器?！罢Z(yǔ)言為人們所接受，包括布爾，控制系統(tǒng)流程圖，這種功能圖及其變化圖表語(yǔ)言。產(chǎn)品的選擇是比較高，可編程控制器為小，低環(huán)數(shù)的應(yīng)用意義。目前，正在推出的產(chǎn)品樣本。除了少數(shù)例外，I/O是仍然專(zhuān)有技術(shù)?！背鲇谶@個(gè)原因，他說(shuō)，PLC的制造商將不會(huì)開(kāi)始銷(xiāo)售通用I/O和其他廠商的系統(tǒng)。“哪里的I/O變得非常聰明，并成為系統(tǒng)的一部分真的很難定義，哪些是I/O，哪些是CPU。GE Fanuc的希望這樣做與天才智能I/O線。”正因?yàn)槿绱?，許多PLC廠商正在制定完整的規(guī)范。批次控制循環(huán)密切合作是最好的例子，那里的順序和維持過(guò)程變量是交織在一起的密切合作，使擁有一個(gè)可編程控制器的邏輯順序做的好處遠(yuǎn)遠(yuǎn)超過(guò)了不具有分布式控制系統(tǒng)的一些缺點(diǎn)?！痹谶^(guò)程的PLC控制到目前為止，PLC的沒(méi)有大量用于連續(xù)過(guò)程控制，會(huì)繼續(xù)嗎？“我感覺(jué)到了，PLC將用于過(guò)程工業(yè)，但不一定過(guò)程控制。如果要求最高性能，必須使用晶體以確保最大時(shí)鐘頻率接近，但不會(huì)超出。首選方法是使用計(jì)時(shí)器電路，能獨(dú)立計(jì)算精確的時(shí)間增量，并生成一個(gè)預(yù)設(shè)的時(shí)間后中斷的時(shí)間。串行輸入/輸出串行通信是指使用少量的通訊線與終端設(shè)備的鏈接。因?yàn)樵S多控制應(yīng)用涉及打開(kāi)和關(guān)閉的單輸出線或在單線，這也經(jīng)常被用來(lái)對(duì)設(shè)施進(jìn)行的測(cè)試，設(shè)置和重置個(gè)別位的內(nèi)存或I/O的應(yīng)用程序。隨機(jī)存取存儲(chǔ)器（RAM）RAM是程序執(zhí)行中的工作變量和數(shù)據(jù)的存儲(chǔ)器。這意味著對(duì)ROM的開(kāi)發(fā)是一種制約，因?yàn)橹圃熘蟛荒苄薷腞OM代碼。ll be the ones left holding a munications structure that39。t justify DCS[distributed control system].With the starting price tags of chose products being relatively high, a programmable controller makes sense for small, low loop count application .The second is where you have to integrate the loop closely with the sequential logical .Batch controllers are prime example ,where the sequence and maintaining the process variable are intertwined so closely that the benefits of having a programmable controller to do the sequential logical outweighs some of the disadvantages of not having a distributed control system.Bill Barkovitz, president of Triconex, predicts that all futur