NTE849

NTE849 Integrated Circuit TV Horizontal/Vertical Countdown Digital Sync System Description: The NTE849 is an integrated circuit in a 14–Lead DIP type package designed for use in TV horizontal/ vetical countdown digital sync systems. In some video playback units, there are incorrect frequency relationships between horizontal and field frequencies. Automatic forced asynchronous mode eliminates jitter when equalizer pulses are correct, but these incorrect frequency relationships exist. Automatic standard mode occurs upon detection of nine or more equalizing pulses during a six–line– width vertical driving period after seven fields of coincidence between integrated vertical (IV) sync and internal counter output. Standard mode is retained for seven fields of missing or mutilated vertical sync pulses. If two or more noise pulses are detected at Pin12 during a 384–line active scan time, a noise detector reverts the system to standard mode at the next field of coincidence (without seven fields of coincidene delay). Thus, the unit stays in standard mode during tuner channel changes. An automatic mode–recognition system places the unit in standard mode for NTSC signals or into non–synchronous mode for non–standard sync signals. An external oscillator (NTE701) supplies an input to Pin9 that is 32 times the horizontal rate. An internal divide–by–16 counter converts this input (32fH) to 2fH for use elsewhere. This 32fH signal is further divided to fH, which is available at Pin11 to drive ...