Analog Devices Advantiv ADV7611 Hardware User's Manual page 118

UG-180
Detailed Mechanism of STDI Block Horizontal/Vertical Lock Mechanism
STDI Horizontal Locking Operation
For the STDI horizontal locking operation, the STDI block compares adjacent line length differences (in XTAL clock cycles) with
the programmed threshold. If 128 consecutive adjacent lines lengths are within the threshold, the STDI horizontally locks to the
incoming video.
LINE 3 – LINE4 ≤ THRESHOLD?
LINE 1 – LINE2 ≤ THRESHOLD?
LINE 1 LINE 2 LINE 3
LINE 2 – LINE3 ≤ THRESHOLD?
Once the STDI locks to the incoming video, it registers the first BL measurement (first eight lines) as latched data (absolute line length: L)
and keeps monitoring and comparing each successive line length with the absolute line length (L/8).
The STDI horizontally unlocks if 128 consecutive lines have a line length greater than the threshold.
LINE 1 LINE 2 LINE 3
FIRST 8 BLOCKS OF LINE LENGTH = BL READBACK VALUE
REGISTERED AS "ABSOLUTE LINE LENGTH"
STDI Vertical Locking
The STDI block compares adjacent field length differences and VSync lengths in line counts and compares them with a threshold. If four
consecutive adjacent field lengths (LCF) and line counts in VSync (LCVS) are within the threshold, the STDI locks vertically to the
incoming video.
LINE 5 – LINE6 ≤ THRESHOLD?
LINE 4 LINE 5 LINE 6
LINE 4 – LINE 5 ≤ THRESHOLD?
MONITORS 128 CONSECUTIVE LINES BEFORE STDI HORIZONTALLY "LOCKS"
Figure 41. STDI Horizontal Locking Operation
LINE 4 LINE 5 LINE 6 LINE 7
L
Figure 42. STDI HSync Monitoring Operation
LINE 7 LINE 8
LINE 129 – L/8 ≤ THRESHOLD? LINE 131 – L/8 ≤ THRESHOLD?
LINE 8
"L/8" ARE REGISTERED AS ABSOLUTE LINE LENGTH REFERENCE FOR
EACH LINE AFTER STDI HORIZONTALLY LOCKS TO
Rev. A | Page 118 of 184
Hardware User Guide
LINE 128 LINE 129
LINE 128 LINE 129 LINE 130 LINE 131
LINE 130 – L/8 ≤ THRESHOLD?
THE INCOMING VIDEO SIGNAL