Emulation circuit with a hold time algorithm, logic and analyzer and shadow memory

摘要

A circuit for an emulation system that has a logic element having a RAM, lookup table, optional delay element and flip-flop/latch. The flip-flop/latch may behave as a flip-flop or as a latch and has separate set and reset signals. The delay element inserts a selectable amount of delay into the data path of the logic element in order to reduce race time problems. The logic elements may be combined to share input signals so as to increase the size of the RAM. The improved circuit also has a playback memory used to store up to a a plurality of copies of sampled data from a logic element so that emulation data can be played back for debugging purposes. Multiple read ports coupled to the logic elements permit a user to read out data from the logic elements during emulation in a time multiplexed manner. The input/output pins may be time multiplexed to carry multiple signals, unidirectionally or bidirectionally.