International Business Machines Corporation

Francis E Baudelot

Patrick Michel

Alain Benayoun

Michel L Costes

Gerard M Montanari

Jean-Fracois LePennec

A method and apparatus for an isochronous traffic of Asynchronous Transfer Mode (ATM) cells in a ring network having at least two stations (101,102) and a ring server (001). The communication within the ring is based on specific isochronous control and data cells. The control cell contains a cell header, sequence number, type of command and parameter fields. The data cell contains a header and a payload divided into N m-bit slots. The isochronous data cells are shared by a plurality of stations on the ring by allocating corresponding slotlist whose identification is carried in the parameter field. Furthermore, the server provides for each station's communication link a transmit identifier in the header associated to a reference in a list of allocated slots for transmission and a receive identifier associated to a reference in a list of allocated slots for reception. The implementation of two pairs of registers whose bits correspond to each byte of the isochronous data cell enables processing in real time transmission and reception of the isochronous data cells and to concatenate the bytes to be stored in a memory and to transmit transparently unmodified or substituted bytes on the ring.

Method and apparatus for allowing communication in an isochronous

In a data communication system, a device for performing a wrap test on at least one line without affecting the other lines that transmit and receive data over at least one multiplex link (4) within time slots allocated to a given line within a given frame. During each time slot, a wrap control bit (W) is set by the communication system to a state that indicates either the wrap test mode or the normal mode of operation. Said bit controls a logic circuit (51) to cause data to be sent either over line (4) or to the receive circuit to perform the test, within each time slot.

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Nice, France

Francis E Baudelot