Michael W Stephens

US Patent:

54105463, Apr 25, 1995

Filed:

Nov 1, 1993

Appl. No.:

8/146531

Inventors:

Keith G. Boyer - Northglenn CO
Kenneth R. Burns - Bloomington MN
Thomas H. Gohl - Westminster CO
Terry R. Gottehrer - Louisville CO
Bernie R. Marasco - Lafayette CO
Michael R. Stephens - Westminster CO
Robert D. Thompson - Loveland CO

Assignee:

Storage Technology Corporation - Louisville CO

International Classification:

G06F 1110

US Classification:

371 371

Abstract:

The present invention discloses a method and apparatus for computing CRC codes for fixed length page buffers of user data where the user data arrives from a transmission device in variable length packets with the packet contents being out of sequential order. The received data is written to a storage device after being restored to the correct sequential order. The data packets are comprised of a header portion and a data portion. The transmission and compression methods commonly employed by the transmission device dictates that the header portion of each packet follows the data portion. The present invention computes a complete CRC code for the data stored in a page buffer in real time as the packets are received by using several registers for saving intermediate CRC codes and circuitry to combine partial CRC codes for those packet portions received out of order. Additional circuitry is provided which reorders the data packet portions received out of order back into sequential order as the data is stored in a page buffer memory in real time. Computing the CRC codes in real time permits the saving of costs associated with other approaches that significantly buffer the incoming packets to permit subsequent reordering and CRC computation.