| 摘要 |
<p>PURPOSE:To attain normal clock switching operation without arrangement of the active system and the spare system by providing a circuit correcting the phase difference of a spare clock to an active clock so as to absorb the mutual phase difference between the clocks generated because of the difference of cable length. CONSTITUTION:The address is decided in advance so that a tap selection circuit 7 selects the spare clock in phase to the active clock among n-kind of the spare clocks having different delay amount at a delay circuit 6. Thus, the spare clock entering the delay circuit 6 via a level conversion circuit 2 is subject to the n- kind of delay times by the delay circuit 6, transmitted to the tap selection circuit 7 respectively, the clock in phase to the active clock is selected by the selection circuit 7 and transmitted to the selection circuit 4. The selection circuit 4 transmits the spare clock detected by the phase difference before the active clock is interrupted to a tank circuit 5. Since the spare clock with almost no phase difference is applied to the tank circuit 5 in place of the active clock, continuous clocks are transmitted from an output terminal.</p> |
