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# Walking Counter Synchronization Scheme

IP.com Disclosure Number: IPCOM000078109D
Original Publication Date: 1972-Nov-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 31K

IBM

## Related People

Douglas, GL: AUTHOR

## Abstract

With the exception of a two-stage walking counter, a walking counter has one regular mode of operation plus one or more "crazy" modes of operation. The number of crazy modes is 2/N/ over 2N integer for -1 for R = 0, and 2/N/ over 2N integer for R not equal to 0, where. R is the remainder of the 2/N/ by 2N division and N is the number of stages in the counter.

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Walking Counter Synchronization Scheme

With the exception of a two-stage walking counter, a walking counter has one regular mode of operation plus one or more "crazy" modes of operation. The number of crazy modes is 2/N/ over 2N integer for -1 for R = 0, and

2/N/ over 2N integer for R not equal to 0, where. R is the remainder of the 2/N/ by 2N division and N is the number of stages in the counter.

The regular mode has 2N states in it, and each crazy mode also has 2N states, except where R not equal O, and then one 4f the crazy modes has R states. In Fig. 1 is shown the desired sequence of a N = 7 walking counter. From this illustration it can be seen that upon startup unless the counter is preconditioned, which is costly, its chances of being in a crazy mode are fourteen out of one hundred twenty-eight.

If a walking counter gets into one of the crazy modes, then it will loop through those 2N states and never achieve any of the 2N states of the regular mode. To assure that a walking counter never stays in a crazy mode but always returns to the regular mode, separate logic must be provided to cause the prescribed progression.

Any two stages of the counter always achieve the four possible combinations in all regular and crazy modes. By taking one of these four combinations as a "sample states," the states of the other stages can be examined to determine if the counter is running in the regular mode or one of the crazy modes, and corrective action can be taken.

In Fi...