Patent ID: 7167477

Claim:
A method for recovering abnormal control cells in an asynchronous transfer mode (ATM) exchange subscriber unit, comprising: transmitting a signal cell or control cell and then sequentially checking a plurality of reception first-in first-out memories (FIFOs) to determine whether a new cell has arrived; recognizing that the current cell is abnormal after said transmitting is performed, if there is no start of cell (SOC) signal in an initial byte of a current cell under the condition that a cell synchronization loss signal is present in the current cell, or if the Soc signal is detected during transfer of the current cell; and discarding the current cell and fully emptying an associated FIFO to recover cell synchronization if the cell synchronization loss signal is abnormal during said recognizing, wherein said discarding includes: setting to 0 all bytes to be transmitted under the condition that said synchronization loss signal is not set if the current cell in transmission is abnormal; and setting no transmission synchronous signal and then returning to said transmitting.