A DEPACKETISER AND A FRAME ALIGNER INCLUDING THE DEPACKETISER

摘要

In terminating an ATM multiplexed data stream at a functional unit, virtual channel data being carried in cells in the data stream, a depacketiser has a plurality of cell buffers each storing the data contained in a single cell and being loaded in the sequence of a message sequence number carried by each cell and emptied in accordance with a depacketiser algorithm to form a data stream; a fill-in cell format generator which on the failure of a valid cell to arrive causes the replacement of the missing cell by a fill-in cell in the data stream; a time-out function generator which is started after each cell has been depacketised and sometimes after fill-in replacement cells have been generated. A cell frame aligner has the depacketiser with a frame alignment signal detector which detects a frame alignment signal in the non-continuous data stream and generates an associated frame start signal and a loss of frame alignement signal as appropriate; and a frame aligner which accepts the non-continuous data stream and its associated frame start signal, except in the presence of a loss of frame alignment signal and aligns the non-continuous data stream to clock and frame start signals of the functional unit.