REV. 0
AD9887
–33–
SYNC DETECTION AND CONTROL
11
7
Analog Interface HSYNC Detect
This bit is used to indicate when activity is detected on
the HSYNC input pin (Pin 82). If HSYNC is held high or
low, activity will not be detected.
Table XXX. HSYNC Detection Results
Detect
Function
0
No Activity Detected
1
Activity Detected
Figure 38 shows where this function is implemented.
11
6
Analog Interface Sync-on-Green Detect
This bit is used to indicate when sync activity is detected
on the Sync-on-Green input pin (Pin 108).
Table XXXI. Sync-on-Green Detection Results
Detect
Function
0
No Activity Detected
1
Activity Detected
Figure 38 shows where this function is implemented.
Warning: If no sync is present on the green video input,
normal video may still trigger activity.
11
5
Analog Interface VSYNC Detect
This bit is used to indicate when activity is detected on
the VSYNC input pin (Pin 81). If VSYNC is held high or
low, activity will not be detected.
Table XXXII. VSYNC Detection Results
Detect
Function
0
No Activity Detected
1
Activity Detected
Figure 38 shows where this function is implemented.
11
4
Digital Interface Clock Detect
This bit is used to indicate when activity is detected on
the digital interface clock input.
Table XXXIII. Digital Interface Clock Detection Results
Detect
Function
0
No Activity Detected
1
Activity Detected
The sync processing block diagram shows where this
function is implemented.
11
3
Active Interface
This bit is used to indicate which interface should be
active, analog, or digital. It checks for activity on the
analog interface and for activity on the digital interface,
then determines which should be active according to
Table XXXIV. Specically, analog interface detection
is determined by OR-ing Bits 7, 6, and 5 in this register.
Digital interface detection is determined by Bit 4 in this
register. If both interfaces are detected, the user can
determine which has priority via Bit 6 in register 12H.
The user can override this function via Bit 7 in Register 12H.
If the override bit is set to Logic 1, then this bit will be
forced to whatever the state of Bit 6 in Register 12H is set to.
Table XXXIV. Active Interface Results
Bits 7, 6,
or 5
Bit 4
(Analog
(Digital
Detection)
Override
AI
000
Soft
Power-Down
(Seek Mode)
010
1
100
0
1
0
Bit 6 in 12H
X
1
Bit 6 in 12H
AI = 0 means Analog Interface.
AI = 1 means Digital Interface.
The override bit is in Register 12H, Bit 7.
11
2
AHS—Active HSYNC
This bit is used to determine which HSYNC should be
used for the analog interface, the HSYNC input or Sync-
on-Green. It uses Bits 7 and 6 in this register for inputs
in determining which should be active. Similar to the previ-
ous bit, if both HSYNC and SOG are detected the user
can determine which has priority via Bit 4 in Register
12H. The user can override this function via Bit 5 in
Register 12H. If the override bit is set to Logic 1, this
bit will be forced to whatever the state of Bit 4 in Register
12H is set to.
Table XXXV. Active HSYNC Results
Bit 7
Bit 6
(HSYNC
(SOG
Detect)
Override
AHS
0
Bit 4 in 12H
0
101
1
000
1
0
Bit 4 in 12H
X
1
Bit 4 in 12H
AHS = 0 means use the HSYNC pin input for HSYNC.
AHS = 1 means use the SOG pin input for HSYNC.
The override bit is in Register 12H, Bit 5.
11
1
AVS—Active VSYNC
This bit is used to determine which VSYNC should be
used for the analog interface; the VSYNC input or output
from the sync separator. If both VSYNC and composite
SOG are detected, VSYNC will be selected. The user can
override this function via Bit 3 in Register 12H. If the
override bit is set to Logic 1, this bit will be forced to what-
ever the state of Bit 2 in Register 12H is set to.
OBSOLETE