GS2960 Datasheet, PDF (31/97 Pages) Semtech Corporation – 3Gb/s, HD, SD SDI Receiver Complete with SMPTE Video Processing

Table 4-4: Lock Detect Conditions
Mode of Operation
Data-Through Mode
SMPTE Mode
DVB_ASI Mode
Mode Setting
SMPTE_BYPASS = LOW
DVB_ASI = LOW
SMPTE_BYPASS = HIGH
DVB_ASI = LOW
SMPTE_BYPASS = LOW
DVB_ASI = HIGH
Bit AUTO/MAN = LOW
Condition for Locked
Reclocker PLL is locked.
Reclocker PLL is locked
2 consecutive TRS words are detected
in a 2-line window.
Reclocker PLL is locked
32 consecutive DVB_ASI words with
no errors are detected within a
128-word window.
NOTE 1: The part will lock to ASI Auto mode, but could falsely unlock for some ASI
input patterns.
NOTE 2: In Standby mode, the reclocker PLL unlocks. However, the LOCKED signal
retains whatever state it previously held. So, if before Standby assertion, the LOCKED
signal is HIGH, then during standby, it remains HIGH regardless of the status of the PLL.
4.7.1 Asynchronous Lock
The lock detection algorithm is a continuous process, beginning at device power-up or
after a system reset. It continues until the device is powered down or held in reset.
The device first determines if a valid serial digital input signal has been presented to the
device. If no valid serial data stream has been detected, the serial data into the device is
considered invalid, and the LOCKED signal is LOW.
Once a valid input signal has been detected, the asynchronous lock algorithm enters a
“hunt” phase, in which the device attempts to detect the presence of either TRS words or
DVB-ASI sync words.
By default, the device powers up in auto mode (the AUTO/MAN bit in the host interface
is set HIGH). In this mode, the device operating frequency toggles between 3G, HD and
SD rates as it attempts to lock to the incoming data rate. The PCLK output continues to
operate, and the frequency may switch between 148.5MHz, 74.25MHz, 27MHz and
13.5MHz.
When the device is operating in manual mode (AUTO/MAN bit in the host interface is
LOW), the operating frequency needs to be set through the host interface using the
RATE_DET[1:0] bits. In this mode, the asynchronous lock algorithm does not toggle the
operating rate of the device and attempts to lock within a single standard. Lock is
achieved within three lines of the selected standard.
4.7.2 Signal Interruption
The device tolerates a signal interruption of up to 10μs without unlocking, as long as no
TRS words are deleted by this interruption. If a signal interruption of greater than 10μs
is detected, the lock detection algorithm may lose the current data rate, and LOCKED
will de-assert until the data rate is re-acquired by the lock detection block.
GS2960 3Gb/s, HD, SD SDI Receiver Complete with
SMPTE Video Processing
Data Sheet
48003 - 6
September 2012
31 of 97