An address substitution apparatus.

摘要

A binary number substitution mechanism includes first and second storage arrays addressed by first and second portions, respectively, of an input binary number, producing a substitute output binary number. The input binary number represents a predetermined number of microinstruction addresses in a read-only store, and the output binary number is representative of microinstruction addresses in a main storage device. Only a limited number of the possible input binary numbers are required to access the first and second storage arrays to read out selectively stored binary numbers to create a limited range of output binary numbers unique to each of the limited number of the input binary numbers. Further, compression of the range of output of binary numbers as substitution for certain ones of the binary input binary number is achieved by addressing the first and second storage arrays by first and second portions of the input binary number to which a certain number of the input signal line of the first and second portions are common.