Apparatus and method for recovering abnormal control cells in asynchronous transfer mode exchange subscriber unit

摘要

An apparatus and method for recovering abnormal control cells in an asynchronous transfer mode (ATM) exchange subscriber unit. A signal cell or control cell is transmitted and a plurality of reception first-in first-out memories (FIFOs) are sequentially checked to determine whether a new cell has arrived. 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, the current cell is determined to be abnormal. If the cell synchronization loss signal is abnormal, the current cell is discarded and an associated FIFO is fully emptied to recover cell synchronization. According to the invention, an internal control cell having a command to be transferred to an ATM exchange subscriber interface, and subscriber interface state information to be reported to a controller, and a signal cell for call control between ATM exchanges are recovered rapidly and effectively when being abnormally transferred to the subscriber interface. Therefore, the subscriber interface can fundamentally be prevented from being erroneously operated and falling into an operation disable state, thereby enhancing stability of the subscriber unit.