| 摘要 |
A television synchronization signal generator circuit is provided for generating television synchronization, blanking, and drive signals. The sync generator is programmable to provide synchronization signals in the PAL, SECAM, NTSC, and PAL-M standards at the appropriate 525 or 625 line rate. A synchronous horizontal counter is used to divide clock pulses having a frequency of 134 times the horizontal line frequency down to the horizontal line frequency. A vertical counter divides a phase advanced signal having a frequency of twice the horizontal line frequency by 525 or 625 to arrive at the vertical field rate. Logic gates decode the horizontal and vertical counter output signals to condition output signal flip-flops which are retimed by the input clock pulses to eliminate phase delays between the clock pulses and the output signals. Reset inputs are provided for synchronizing the sync generator to an external signal source. In a preferred embodiment of the invention, a programmable counter is provided for dividing the chrominance subcarrier signal by an appropriate integer to develop a signal having a frequency of one-quarter the horizontal line rate, H/4. The H/4 signal may be used to synchronize the sync generator to the chrominance subcarrier signal. |
