User manual

Threshold Point
As the input signal is delayed in time, there comes a point where the output timing will have to jump
by exactly one line (the output must always come after the input). This point is called the threshold
point. When comparing the input signal with the external reference, the threshold point is 26
microseconds before the falling edge of the external reference. In other words, if the input signal’s
falling H sync edge is 26 microseconds before the external reference’s falling H sync edge, the input
signal is said to be on the threshold point.
In addition, there is built in hysteresis so that if an input source is on the threshold point, the output
timing will be constant and will not jump back and forth by a line if the input signal varies slightly.
However, if the input signal is exactly on the threshold point, the output timing may vary from one
power up sequence to the other. In other words, the card may power up with different timing than the
previous time it was powered-up. To avoid this condition, it is recommended to keep the input signal
away from the threshold point. Two microseconds can be considered a safe distance.
Note
In Line Sync mode, you should keep the falling edge of the
incoming video away from the threshold point.
Frame Delay (ADC-8032B-S)
The Frame Delay mode is identical to the Line Delay mode, except that the output timing can be
delayed by up to a full frame of video. By using almost a full frame of delay, it is possible to set
apparent negative timing, making it look like the output occurs before the input, although delayed by 1
frame.
Frame Sync (ADC-8032B-S)
The Frame Sync mode makes it possible to use asynchronous sources. The output timing is generated
entirely based on the external reference. Whether a synchronous or an asynchronous source is used,
output timing is constant. The delay through the card will be the minimum latency (in the order of
microseconds) to a full frame of delay.
4-16 • Using Banks ADC-8032B User Manual (Iss. 02B)