本设计为六位约翰逊(Johnson)计数器，首先给大家介绍一下什么是约翰逊计数器，它又称扭环计数器,是一种用n位触发器来表示2n个状态的计数器。它与环形计数器不同,后者用n位触发器仅可表示n个状态。2~n进制计数器(n为触发器的个数)有2~n个状态。若以6位二进制计数器为例,它可表示64个状态。但由于8421码每组代码之间可能有二位或二位以上的二进制代码发生改变,这在计数器中特别是异步计数器中就有可能产生错误的译码信号,从而造成永久性的错误。而约翰逊计数器的状态表中,相邻两组代码只可能有一位二进制代码不同,故在计数过程中不会产生错误的译码信号。鉴于上述优点,约翰逊计数器在同步计数器中应用比较广泛。(This design is a six-bit Johnson counter, first of all to introduce what is the Johnson counter, it also called the torsion ring counter, is a kind of n-bit trigger to represent the 2n state of the counter. It differs from a ring counter, which uses n-bit triggers only to represent N states. The 2~n feed counter (n is the number of triggers) has a 2~n state. For example, a 6-bit binary counter can represent 64 states. However, because there may be two-bit or more than two bits of binary code between each set of code in 8421 yards, it is possible to produce the wrong decoding signal in the counter, especially in the asynchronous counter, resulting in a permanent error. In the state table of the Johnson counter, the adjacent two groups of code may only have one binary code, so there will be no wrong decoding signal in the counting process. In view of the above advantages, Johnson counter is widely used in synchronization counter.)