Note this FAQ relates to the ADV7180, ADV7182, ADV7280, ADV7280-M, ADV7281, ADV7281-M, ADV7281-MA, ADV7282 and ADV7282-M models. These devices will be referred to as ADV728x/ADV728x in this FAQ.
The easiest way of determining if the ADV718x/ADV728x has locked or lost lock to a video source is to program the INTRQ interrupt pin.
See http://ez.analog.com/message/60384#60384
Alternatively the LOST_LOCK and IN_LOCK bits can be used to determine if the ADV718x/ADV728x has locked, or lost lock, to a video source. Note in order for the LOST_LOCK and IN_LOCK bits to work correctly the ADV718x/ADV728x must be programmed with an Analog Devices recommended script.
LOST_LOCK bit can be found at User Map, Register 0x10, Bits [1]. IN_LOCK bit can be found at User Map, Register 0x10, Bits [0].See "Global Status Register" section of the ADV7180 datasheet (and ADV7182 datasheet) for more information.
The table below show the operation of the LOST_LOCK and IN_LOCK bits as the active video source is connected or disconnected.