Importance

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Abstract

In order to more effectively use read only memory space of a personal computer system, ROM code is selectively located or mapped to either an address boundary which is an even or odd integer multiple of one half the capacity of the read only memory device in which the ROM code is stored. The ROM code is stored in the read only memory device in two fields. In a first field, the ROM code is broken up into two segments, and the first segment precedes the second segment. In the second field, the same two segments are stored, but the second segment is stored preceding the first segment. A register, for storing page select bits, provides an input to an address decoder and an input to an adder, which adds unity to the contents of the register and provides its outputs to the address decoder as well. Accordingly, the address decoder will respond to either the page which is identified by the page select bits or the page following the identified page. The LSB of the page select bits is used in addressing the read only memory device to select between the first field (selected when the LSB is zero) or the second field (selected when the LSB is unity).

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First Claim