JPS6484353A - Memory access system - Google Patents

Abstract

PURPOSE:To attain access control corresponding to the attribution of a memory to a memory space where a memory having optional attribution is arranged by defining the memory attribution to another memory space so that the memory attribution can be rewritten by a processor. CONSTITUTION:One or plural unit memory spaces for storing 2<m> words are defined as a memory area and a memory space for storing 2<n> words (n>m) corresponding to a RAM 41, a ROM 42 and a memory mapped IO 43 to be memory devices consisting of memory elements having different attribution is made access. On the other hand, the system is provided with a register 31 to be a memory device having an area for storing 2<n-m> words in a memory space other than said memory space and capable of converting the stored contents of the memory space and applying a signal consisting of high-order (n-m) bits corresponding to the unit memory space out of address signals to the memory space. Since the memory attribution can be defined in a memory space other than a necessary memory space and rewritten by the processor, memory access corresponding to the attribution for optional memory arrangement can be attained.