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Asynchronously Clocked Up/Down Counter

IP.com Disclosure Number: IPCOM000064846D
Original Publication Date: 1985-Sep-01
Included in the Prior Art Database: 2005-Feb-19

Publishing Venue

IBM

Related People

Authors:
Dillon, GE [+details]

Abstract

Circuitry within a tape control unit required an up/down counter which was to increment one count for each increment strobe and decrement one count for each decrement strobe wherein the total count would be known of one strobe relative to the other. This design task could normally have utilized a standard up/down counter architecture; however, the increment and the decrement strobes used to clock the counter are asynchronous to one another. A number of solutions or possible design alternatives were considered; however, all of the other designs relied on a significant amount of control and synchronization logic. The speed of the incoming strobes coupled with the synchronization problem made the ever looming threat of metastability and an inoperable counter a reality.