On the Minimization of the Control Store in Microprogrammed Computers

A new approach is presented for the minimization of the word length of the control store in microprogrammed computers. Given the set of microinstructions and the set of microcommands of a microprogrammed computer a minimal subset of microcommands are determined so that every other microcommand not contained in this minimal subset to be generated from it by a single AND or OR gate. The problem of finding such minimal subsets of microcommands is formulated as a Boolean function simplification problem and is based upon an extension of the notion of the minimal dependence sets of a Boolean function.