A Study On Retiming Algorithm In The Synchronous Sequential Circuit

With the growing of scale of Integrated Circuits and popularizing of its application, there is a great demand for making short design period and decreasing design difficulty. High-Level Synthesis (HLS) systems for digital IC are playing such a role. But circuitry net table which is synthesized by synthesizer is not necessarily achieve the demand of designer, so aim for the speed demand of destination, the sequence circuit which is synthesized demand speed optimization. The method of optimization is classified into two categories: (1) combinational optimization method, which is the optimizational method of combinational circuit is directly used for the sequence circuit. (2)Retiming, which can optimize the rapidity, area and functional extravagance through moving the sequential elements and change the number of sequential elements.Optimize Synchronous sequential circuit with retiming was introduced by Leiserson and Saxe in 1983, and Retiming optimizational algorithm was summarized comprehensively in 1991. Retiming has been used for many fields recently. Regretfully, the Retiming algorithm can not be used together with existing combinational optimization techniques. But, Retiming should be used together with existing combinational optimization techniques and form an optimizational flow in practical circuitry system to exert fully the advantage of both. In the paper, the new Retiming which can be used well together with existing combinational optimization techniques is introduced.Retiming can eliminate sequence conflict when sequence constraint condition for example destination clock period is scheduled, the retiming is called sequence adjust strategy. The effectivelyretiming determining algorithm is key of retiming, so it is the key of sequence adjust strategy. The effectively retiming determining algorithm can be mainly classified into two categories: one is based on minimal weight path algorithm, the other is based on simple retiming. A retiming algorithm FAM which based on simple retiming is introduced in the paper, the time computation complexity of the algorithm is better than the classical algorithm FEAS.In order to eliminate the sequence conflict of synchronous sequential circuit and shorten the designable time of Integrated Circuits, the algorithms of retiming is deeply researched in this paper.