Vertical Synch Timing Controller for Format Change
Original Publication Date: 1988-Jun-01
Included in the Prior Art Database: 2005-Feb-15
This method is utilized for a change of screen format, i.e., Scan Line/Row Number (L/R#) and Row Number (Row#) without a shaky screen display. The screen's shake is caused by Vertical Sync (VS) pulses which the values of L/R and Row disorders. Therefore, in this method, a VS Generator is made independent of both a Line Counter (L-CNTR) and a Row Counter (R-CNTR) associated with L/R and Row registers, in order to generate clean VS pulses. A Total Line Counter (TL-CNTR) in the figure repeats to count up to the same value of a Total Line Number (TL#) in a TL register and then to be cleared. The repeating frequency of this TL-CNTR determines the frequency of the VS pulses.