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【正文】 Alle bradeley和辛辛那提米拉克龍公司已經(jīng)擁有，并有傳言說，通用的電氣計(jì)劃將沿著同樣的思路。由于肯Jannotta。 由于不太可能將個(gè)人的PLC廣泛的交談，制造商更專注于專有的網(wǎng)絡(luò)。我們聽說了很多規(guī)范在過去數(shù)年，許多公司都紛紛跟進(jìn)。富瑞安的經(jīng)理認(rèn)為PLC將越來越多地使用食品等行業(yè)，化工，石化。 編程語(yǔ)言更高水平的PLC編程語(yǔ)言已經(jīng)推行有一段時(shí)間了，但最近的流行，如雨后春筍般。更好的計(jì)時(shí)器有自動(dòng)加載初始值的功能。這可以作為一個(gè)硬件設(shè)施或U(S)ART（通用執(zhí)行（同步）異步接收器/發(fā)送器）來減緩像處理器（和應(yīng)用程序）中低級(jí)別細(xì)節(jié)費(fèi)時(shí)。大多數(shù)設(shè)立的是一個(gè)機(jī)制，至少允許靈活的選擇讓那些引腳輸出，那些引腳輸。在哈弗結(jié)構(gòu)的微型電腦通常做為集中內(nèi)存。這種類型的設(shè)備可以表現(xiàn)為單芯片微型計(jì)算機(jī)盡管有限制的I/O和外部修改這些設(shè)備的電路。一些廠家用哈弗結(jié)構(gòu)，這種特性在硬件中分離了程序內(nèi)存和數(shù)據(jù)內(nèi)存，依據(jù)同樣的原理廣泛的適用于一般目的的電腦和微電腦。 but Frank Newburn, vice president of Omron39。ve gotten, says Ken Jannotta, manger, product planning, series One and Series Six product ,at GE Fanuc North America,39。 EPROM (Erasable programmable ROM ) sockets or devices with EPROM instead of ROM .These devices are naturally more expensive than equivalent ROM device, but do provide plete circuit equivalents. EPROM based devices are also extremely attractive for lowvolume applications where they provide the advantages of a singlechip device, in terms of onchip I/O, etc. with the convenience of flexible user programmability.Random access memory (RAM)RAM is for the storage of working variables and data used during program execution. The size of this memory varies with device type but it has the same characteristic width (4,8,16 bits etc.) as the processor ,Special function registers, such as stack pointer or timer register are often logically incorporated into the RAM area. It is also mon in Harvard type microputers to treat the RAM area as a collection of register。 it is unnecessary to make distinction between RAM and processor register as is done in the case of a microprocessor system since RAM and registers are not usually physically separated in a microputer.Central processing unit (CPU)The CPU is much like that of any microprocessor. Many applications of microputers and microcontrollers involve the handling of binarycoded decimal (BCD) data (for numerical displays, for example) ,hence it is mon to find that the CPU is well adapted to handling this type of data .It is also mon to find good facilities for testing, setting and resetting individual bits of memory or I/O since many controller applications involve the turning on and off of single output lines or the reading the single line. These lines are readily interfaced to twostate devices such as switches, thermostats, solidstate relays, valves, motor, etc.Parallel input/outputParallel input and output schemes vary somewhat in different microputer。is that PLCs will be used in the process industry but not necessarily for process control.Several vendors obviously betting that the opposite will happen have introduced PLCs optimized for process application .Rich Ryan, manger, mercial marketing, Allenbradley Programmable Controls Div., cites PLCs39。s Industrial Division ,reports that because of the lack of a firm definition ,Omron39。一些廠家則采用像Princeton結(jié)構(gòu)，不劃分程序內(nèi)存和數(shù)據(jù)內(nèi)存。小內(nèi)存裝置的應(yīng)用在永久性內(nèi)存的制造中是非常普遍的；但此I/O和其它芯片相比，基于微處理器的傳統(tǒng)電路仍然可以在我節(jié)省大量成。在微機(jī)中，由于RAM和寄存器沒有被物理上劃分，所以像在微處理系統(tǒng)中沒必要把它們分別看待。這可能適用于所有或部分端口。它只需要選擇一個(gè)波特率及其他可能的選擇（停止位，奇偶校驗(yàn)等），載入（或讀?。┐邪l(fā)送器（或接收）的緩沖器。這將緩解重新加載計(jì)數(shù)器和評(píng)估所用的時(shí)間，計(jì)時(shí)器重新啟動(dòng)之前這是必要的。正如雷蒙德萊韋耶，副總裁兼總經(jīng)理，西門子能源和自動(dòng)化公司，可編程控制正在為更復(fù)雜的操作使用，梯形邏輯比語(yǔ)言變得更加實(shí)際，有效和強(qiáng)大的。Ryan認(rèn)為有兩種類型的應(yīng)用程序中，他們是合適的。但是，不少人失望的發(fā)現(xiàn)完成地圖規(guī)范并沒有立即出現(xiàn)。按照薩爾Provanzano說法，用戶擔(dān)心，如果他們不從規(guī)則上和供應(yīng)商妥
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