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Syndrome/ Check Bit Generator With Minimum Gate Delay

IP.com Disclosure Number: IPCOM000122583D
Original Publication Date: 1991-Dec-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 2 page(s) / 59K

Publishing Venue

IBM

Related People

Fifield, JA: AUTHOR [+2]

Abstract

An architecture is shown for an on-chip error correction circuit (ECC) where the correction system circuit delays are minimized by utilizing the same Exclusive OR (XOR) logic gates for both read and write operations.

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This is the abbreviated version, containing approximately 70% of the total text.

Syndrome/ Check Bit Generator With Minimum Gate Delay

      An architecture is shown for an on-chip error correction
circuit (ECC) where the correction system circuit delays are
minimized by utilizing the same Exclusive OR (XOR) logic gates for
both read and write operations.

      Implementation of an ECC system on a DRAM to overcome defects
in the storage cells and array circuits can be done using a Hamming
type code; however, these codes require a comparison between the
check bits stored in memory at the time the data word was stored with
the check bits generated from the data word at the time of retrieval.
In the new system disclosed, syndrome bits are produced during the
read operation by the simultaneous XORing of data and check bits. By
applying a logical "0" to the check bit inputs through the
utilization of one additional XOR circuit and using the same XOR
logic tree for write back, the problem of excessive gate delays to
generate syndrome/check bits is solved.

      It can be shown that the mathematical operation of XOR on N
data bits followed by XOR operation with the K stored check bits is
equivalent to the XOR of the N data word with the K check bits. By
choosing an ECC code wide enough to accommodate the K extra inputs,
the extra XOR gate stage can be eliminated. A diagram of this
operation is shown for a read operation in Fig. 1.

      It is required in a memory system with ECC to generate check
bits for each data word upon write back to th...