| 摘要 |
PROBLEM TO BE SOLVED: To easily and surely detect and prevent a pseudo synchronization state by providing a forced hunting circuit controlling a 1st frame synchronization circuit to be in hunting. SOLUTION: In the case synchronization is taken in a 1st frame synchronization circuit 101 while no frame synchronization is taken in a 2nd frame synchronization circuit 104, it is discriminated that a pseudo synchronization state is caused in the 1st frame synchronization circuit 101. In the operation of a forced hunting control circuit 102 in this case, the circuit 102 detects at first the 1st frame synchronization circuit 101 is in a frame synchronization state and the 2nd frame synchronization circuit 104 is in a frame asynchronization state. Only when the 2nd frame synchronization circuit 104 is in a frame asynchronization state even after a prescribed time of τ1, forced hunting is applied to the 1st frame synchronization circuit 101 for a prescribed time τ2 to lock the frame of the 1st frame synchronization circuit 101 forcibly. |
