EQUIVALENT PULSE PERIOD INVALIDATION DISCRIMINATION CIRCUIT

摘要

PURPOSE: To provide an equivalent pulse period invalidation discrimination circuit capable of correctly discriminating a frequency of a horizontal synchronizing signal by a horizontal frequency discrimination circuit. ;CONSTITUTION: When the frequency of the horizontal synchronizing signal is discriminated from a composite synchronizing signal in which an equivalent pulse is inserted into a vertical blanking period at the half period of the horizontal synchronizing signal by the horizontal frequency discrimination circuit A, horizontal frequency discrimination operation by the horizontal frequency discrimination circuit A is invalidated based on an output of a horizontal frequency discrimination invalidation period generation circuit 24 in the interval when the equivalent pulse detected by an equivalent pulse period detection decoder 23 exists, and the operation is prohibited by the output of a latch pulse enable circuit 25.;COPYRIGHT: (C)1995,JPO