JPS6448153A - Memory controller - Google Patents

Abstract

PURPOSE:To improve the reliability of a memory part by subjecting data, where error occurs, to one-bit correction and writing this corrected data and reading out the same data again and substituting an alternative memory for a pertinent memory element at the time of detecting hard error in this read data. CONSTITUTION:Alternative memories 211-241 are provided in a memory part 2, and a patrol control part 4 reads data from the memory part 2 and reads out corrected data after one-bit error correction in an error correction detecting circuit 5 and detects the presence or the absence of hard error. The error bit based on syndrome data and the upper address indicating the position of an IC memory where hard error is detected are stored in a syndrome storage means 6, and IC memories 21-24 are switched to alternative memories 211-241 by a data bus switching part 7 in accordance with contents of the syndrome storage means 6. Thus, the memory element where hard error occurs is substituted to improve the reliability.