Structures and methods to avoiding hold time violations in a programmable logic device

Abstract

Structures and methods of avoiding hold time violations in a design implemented in a PLD. In a programmable device, the delay of a signal path varies, e.g., depending on the separation between the source and destination of the signal. An optional delay element is provided between a programmable interconnect structure and a destination logic element having a clock skew relative to the source. The optional delay element is programmed by the implementation software to introduce a delay on the signal path when necessary to meet the hold time requirements for the destination logic element. The optional delay is designed to be large enough to overcome hold-time violations even for the largest possible clock skew and the smallest possible signal delay. When no hold time violation occurs, the optional delay element is configured to bypass the additional delay, to avoid imposing a large setup requirement on the signal.