A method of synthesis of complicated multilevel combinatorial circuits (method M6)

Essential limitation of application of the methods considered above is limitation on a maximum rank (number of literals) conjunctions of realizable functions. In case of violation of the given condition two approaches to solution of a problem are possible(probable):
1) synthesis of the auxiliary combinatorial circuit on PLD for implementation of all conjunctions given by a Booleen Function System;
2) synthesis of the auxiliary combinatorial circuit on PLD for lowering a rank of long conjunctions up to the given value.
In case of the first approach the further synthesis may be carried out or by join of outputs PLD on OR (method M2) when mounting connection of outputs is authorized, or join of conjunctions on OR with the help PLD of the second level (methods M3 and M4), or by synthesis of the circuit with usage of internal chains of feedbacks PLD (method M5) when mounting connection of outputs PAL is forbidden. In case of the second approach the maximum rank of conjunctions may be reduced up to the given value, and the further synthesis to be carried out according to one of methods M2 - M5.
Method M6 includes three stages. At the first stage set Y* of realizable functions in complete correspondence with one of the methods M2 - M5 used at the third stage is defined(determined). At the second stage conjunctions of Booleen Function System Y* by the multilevel circuit on PLD are realized. Thus separate conjunctions or their parts may be used as factors for implementation of other conjunctions. At the third stage of synthesis one M2 - M5 from methods is applied.
Main positive quality of method M6 is absence of limitations on application, i.e. the given method is applicable for synthesis of very complicated Booleen Function Systems in any digital systems and on anyone PLD.

To disadvantages of method M6 concern:

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