Browse Prior Art Database

Counter Synchronization for Memory Card Soft Error Scrub

IP.com Disclosure Number: IPCOM000035288D
Original Publication Date: 1989-Jul-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Arlington, DL: AUTHOR [+2]

Abstract

Three checks are added to a normal refresh cycle to assure that counters in two logic chips which each control half of the data path are in synchronization. Thus, both halves of error correction code (ECC) words are assured to come from the same address. By adding these checks, errors, e.g., writing back data and checkbits that do not belong to each other, are avoided.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 62% of the total text.

Page 1 of 1

Counter Synchronization for Memory Card Soft Error Scrub

Three checks are added to a normal refresh cycle to assure that counters in two logic chips which each control half of the data path are in synchronization. Thus, both halves of error correction code (ECC) words are assured to come from the same address. By adding these checks, errors, e.g., writing back data and checkbits that do not belong to each other, are avoided.

A scrub consists of an on-card fetch at a memory location, single bit error correction if needed, and then a restore of the corrected data back to memory. If the single bit error is related to a hard fail, the scrub has no net effect. A single bit error occurring due to a soft fail is written back correctly during the scrub operation. The rate at which scrub operations are performed is controlled by two counters on each chip and by two bits in a special function register. When a pre- determined portion of each counter matches, the scrub operation is activated, and the counter is updated. The scrub is done based on a row address from one counter and the column address from the other counter. The special function register bits are used to control the comparison field, and thus control the comparison rate.

If counters get out of synchronization, which creates no problem when used for refresh only, two halves of ECC words may not originate from the same address which does cause problems during a scrub. In most cases, the data in error is caught,...