The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Mar. 11, 1997
Filed:
Jun. 04, 1993
Peter L Higginson, Herts, GB;
Anthony N Berent, Hampshire, GB;
Digital Equipment Corporation, Maynard, MA (US);
Abstract
A device 11 includes a sync unit 20 to identify and achieve synchronization with the cell boundaries of a 53-byte ATM cell stream. Each cell starts with a 5-byte header in which the 5th byte is a CRC byte. Instead of testing all possible bytes to see whether they are cell boundaries, a CRC circuit 21 computes CRCs for successive 5-byte blocks, under the control of a 5-state header counter 22. If such a block is a header, its CRC is a predetermined value, and a match signal is sent to a logic circuit 23, which starts a 53-state cell counter 24 and stops the header counter 22. A 4-state repeat counter 25 checks that the next 5 blocks checked by the CRC circuit 21 are also headers, as confirmation. Synchronization is achieved within at most 5 cells, because the test period of the testing circuitry (which could be longer than the header length) is coprime with the cell length.