Dual comparator scheme for detecting a wrap-around condition and

Abstract

A device and method for comparing cancel tags, and for canceling data from a finite wrap-around data buffer. The data buffer stores tag values that are continuous, or sequential. A cancel tag is used to cancel all tags with a value 'greater-than' the cancel tag. In comparing cancel tags of a wrap-around buffer, however, the comparator must take into account wrap-around conditions. When a wrap-around condition occurs, tags that have a lower value may be 'greater-than' the cancel tag. The present invention advantageously adds an additional bit to the tags stored in the data buffer and the cancel tag. The additional bit is toggled whenever a wrap-around condition occurs. By comparing the additional bit of the tag to the additional bit of the cancel tag, a wrap-around condition can be detected without extensive additional circuitry. The comparison of the additional bit indicates whether the comparator should cancel tags that are greater-than or less-than the cancel tag. The cancel tag causes the buffer pointer to change state and point to the storage element associated with the cancel tag, and causes the tag generator to change state.