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“复位表法”是在布尔代数与卡诺图的基础上,经过反复实践推导出来的。该方法从79年初步总结出来到现在,作了大量的实验,其结果都符合要求。该方法和大专院校课本中向学生传授的“卡诺图法”比较,方法简单,容易掌握,使用方便,设计速度快。而且不受进制数的限制。电子计数器的用途是十分广泛的,在数据处理系统、电子计算机、数字式仪表以及各种自动化装置中都要用到它。目前电子计数器设计的方法很多,如卡诺图法、波形图法和编码表法等,用的最多的是卡诺图法。所以在大专院校的课本中主要以卡诺图法向学生进行传授。但是,不管哪种方法,都离不开布尔代数的基本原理与公式。在逻辑电路的设计与研究中,经常要用到的工具是布尔代数与卡诺图,布尔代数是1948年数学家布尔(Boole)最先提出的,所以称为布尔代数(又称逻辑代数)。范奇(Veitch)和卡诺(Karnaugh)在逻辑电路的简化上又进一步提出来一种图表的形式,所以称其为卡诺图。布尔代数的优点是没有局限性,但在解决一些比较复杂的逻辑电路的设计时,不仅需要熟练的运用其公式和定理,而且还要凭借于设计人员的经验和运算技巧;卡诺图法的优点是简单直观,但是变量多于四个以后,就失去了这种优点,所以卡诺图法也就变得实用意义不大了。用卡诺图法设计电子计数器,仍然存在着上述同样的缺点。“复位表法”是为克服卡诺图法存在的缺点,经过几年的反复实践,分析推导出来的一种电子计数器设计的新方法。电子计数器的种类很多,这里只介绍同步和异步两种计数器的设计方法。同步计数器内各触发器的CP输入端系并联接往脉冲源CP。当计数脉冲输入时,各触发器是同步工作的,所以在同步计数器的设计时,只考虑各触发器控制端的接法就行了。异步计数器内各触发器,在输入信号的作用下是串行逐级翻转的,所以在设计时除必须找出各触发器的控制端的接法外,还要决定各CP端的接法。因此设计方法和同步计数器的设计不一样而且比较复杂。由于上述原因,同步和异步计数器的设计方法分开介绍,并采用复位表法与卡诺图法相比较的办法,以便了解它们之间的关系与各自的特点(文中全采用8421编码,以集成Jk触发器为元件,设计过程采用正逻辑)。
“Reset Table” is based on Boolean algebra and Karnaugh map, derived through repeated practice. The method was initially summarized from 79 years to now, a large number of experiments, the results are satisfactory. The method and college textbooks taught to students “Karnaugh map method”, the method is simple, easy to grasp, easy to use, design speed. And not limited by the number of entries. Electronic counters are used for a very wide range of applications in data processing systems, electronic computers, digital meters, and various automation devices. At present, there are many ways to design electronic counters, such as Karnaugh map method, wave chart method, code table method and so on. The most used method is Karnaugh map method. Therefore, in the textbooks of colleges and universities mainly to teach Carnot map to students. However, no matter what method, can not be separated from the basic principles and formulas of Boolean algebra. In the design and research of logic circuits, the frequently used tools are Boolean algebra and Karnaugh map. Boolean algebra was first proposed by Boole, a mathematician in 1948, so called Boolean algebra (also called logic algebra) . Veitch and Karnaugh further proposed a graphical form of the simplification of the logic, so it was called a Carnot map. The advantages of Boolean algebra are not limited, but in solving some complex logic circuit design, not only need to be skilled in formula and theorem, but also by virtue of the designer’s experience and computing skills; Karnaugh map method The advantage is simple and intuitive, but when you have more than four variables, you lose that advantage, so the Karnaugh map has little practical use. Using the Karnaugh map method to design an electronic counter still suffers from the same drawbacks described above. “Reset Table” is to overcome the shortcomings of the Karnaugh map method, after several years of repeated practice, analysis derived a new method of electronic counter design. There are many types of electronic counters, here only introduced synchronous and asynchronous counter design. Synchronous counter flip-flop CP input parallel connected to the pulse source CP. When the count pulse input, the flip-flop is synchronized, so the design of synchronous counter, only consider the flip-flop control side of the connection on the line. Asynchronous counter flip-flop, the role of the input signal is a series of step-by-step flip, so in addition to the design of the trigger must be found out the control side of the connection, but also decided to connect the CP side. Therefore, the design method and synchronization counter design are not the same and more complex. Due to the above reasons, synchronous and asynchronous counter design methods introduced separately, and the use of resettable table method compared with the Karnaugh map in order to understand the relationship between them and their own characteristics (text 8421 encoding to integrate Jk trigger Device as a component, the design process using positive logic).