Bell Telephone Laboratories

Thomas W Fleming

Ronald P Cenker

Frank R Huff

The storage space of the instant system is considered, for refresh purposes, to contain 512 groups of 26 bit digital words with each group containing 128 such words. Memory refresh is implemented by sequentially refreshing the groups of digital words at the rate of one group every 2.8 microseconds, giving an expected total memory refresh time of approximately 1.43 milliseconds. A particular digital word from each group of digital words refreshed is read from the memory and transmitted to a parity check circuit which generates fault signals for any digital word having faulty parity. At the end of each of the approximately 1.43 millisecond refresh cycles, the particular word read from each group refreshed is changed so that at the end of 128 full refresh cycles (approximately 184 milliseconds), the parity of every digital word in the memory has been checked. Further, circuitry is provided to store the location of the first failing digital word in a trap register in response to an indication of faulty parity.

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Naperville, IL, United States of America

Thomas W Fleming