HORIZONTAL SYNCHRONIZING SIGNAL FREQUENCY DETECTION METHOD AND HORIZONTAL SYNCHRONIZING SIGNAL FREQUENCY DETECTION CIRCUIT

摘要

PROBLEM TO BE SOLVED: To detect a frequency of a horizontal synchronizing signal with high precision by starting 1st and 2nd counters simultaneously. ;SOLUTION: First and second counters that count respectively a horizontal synchronizing signal are started, and let a count of a free running counter for a clock period T_f be (b) when a count of the 1st counter is (a), and let a count of a free running counter be (b+n) when a count of the 2nd counter is (a+m). In the case of obtaining a value m/(n×T_f) as a frequency fH of the horizontal synchronizing signal, after the 1st and 2nd counters are started (steps 20, 30), the counts of the 1st and 2nd counters are compared (step 40), and start of the 1st and 2nd counters and the comparison between the counts of the 1st and 2nd counters are repeated till the counts of the 1st and 2nd counters are coincident with each other.;COPYRIGHT: (C)1999,JPO