Double-edge-triggered Gray code counter

Abstract

The invention discloses a double-edge-triggered Gray code counter. A modulo-N counter is formed by combining N+1 groups of triggers. Each group of trigger mainly comprises two latches with different controlled conditions and an additional logic circuit, and has forward output and backward output, wherein the backward output is a half cycle ahead of the forward output. The first group of trigger outputs the CNT[0]th bit of the counter, the Nth group of trigger outputs the CNT[N-1]th bit of the counter, and the output of the (N+1)th group of trigger serves as the input of the first group of trigger. The input of a second group of trigger is obtained by NOR gate operation over the backward output of the first group of trigger and the CNT[N+1]th bit. The input of an Mth stage is obtained by performing NAND gate operation on the backward output of the CNT[0]th bit and the forward output of the CNT[M-2]th to CNT[1]st bits and on the backward output of the CNT[0]th bit and the backward output of an (N+1)th stage and then performing the NOR gate operation on the output subjected to the NAND gate operation and the backward output of the trigger of an (M-1)th stage.

Description

Technical field [0001] The invention relates to a counter in a logic circuit, in particular to a Gray code counter. Background technique [0002] Traditional binary counters have defects in engineering applications. In some areas, such as high-stability engineering control, it is difficult to ensure the stability and uniqueness of counting, because every count of binary counters is accompanied by multi-bit flips, There may be a variety of transition states in the process. These transition states will increase the uncertainty of the counting result. For example, from 011 to 100, all three bits are flipped. If the time of each bit change is biased, it will appear as 000,101,110 and other transition states, these transition states will cause serious engineering accidents in industrial control, and when used on traffic lights, they will lead to uncertain changes in traffic lights. [0003] The Gray code counter has successfully solved this defect of the binary counter. The counting pr...

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Problems solved by technology

[0011] In the above two methods, the first one has a transition state in the converted Gray code because there is a transition state in binary counting, and the second Gray code counter can obtain the Gray code counting result without a transition state, but it can only be used for Counting on a single clock edge increases the length of the counting cycle

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