Patent ID: 7778284

Claim:
A method, comprising: synchronising start of cell times in input/output circuits with cell transmission periods in a cross-connection circuit; transferring cells between said input/output circuits by said cross-connection circuit in cell transfer periods; changing configurations of said cross-connection circuit between cell transfer periods in cross-connection configuration periods; sending cells from a sending input/output circuit of said input/output circuits at start of cell times; receiving said sent cells in said cross-connection circuit; oscillating between a loopback configuration and a no-transmission configuration; transferring the received cells back to said sending input/output circuit in said loopback configuration and not transferring the received cells back to said sending input/output circuit in said no-transmission configuration; receiving back transferred cells in said sending input/output circuit during said loopback configuration; checking said cells transferred back during said loopback configuration in said sending input/output circuit for a transmission error; and shifting an offset of said start cell times in case a transmission error occurred, until transferring back at least one cell is wholly carried out within a cell transfer period.