AD9981
Preliminary Technical Data
Rev. 0 | Page 24 of 44
Hexadecimal
Address
Read and
Write or
Read Only
Bits
Default
Value
Register Name
Description
0x11
R/W
7:0
0010 0000
Sync Separator
Threshold
This register sets the threshold of the sync separator’s digital
comparator.
0x12
R/W
7
0*** ****
Hsync Control
Active Hsync Override.
0 = The chip determines the active Hsync source.
1 = The active Hsync Source is set by 0x12, Bit 6.
6
*0** ****
Selects the source of the Hsync for PLL and sync processing. This
bit is used only if 0x12, Bit 7 is set to 1 or if both syncs are active.
0 = Hsync is from Hsync input pin.
1 = Hsync is from SOG.
5
**0* ****
Hsync Polarity Override.
0 = The chip selects the Hsync input polarity.
1 = The polarity of the input Hsync is controlled by 0x12, Bit 4.
This applies to both Hsync0 and Hsync1.
4
***1 ****
Hsync input polarity: this bit is used only if 0x12, Bit 5 is set to 1.
0 = Active low input Hsync.
1 = Active high input Hsync.
3
**** 1***
Sets the polarity of the Hsync output signal.
0 = Active low Hsync output.
1 = Active high Hsync output.
0x13
R/W
7:0
0010 0000
Hsync Duration
Sets the number of pixel clocks that Hsync out is active.
0x14
R/W
7
0*** ****
Vsync Control
Active Vsync Override.
0 = The chip determines the active Vsync source.
1 = The active Vsync source is set by 0x14, Bit 6.
6
*0** ****
Selects the source of Vsync for the sync processing. This bit is
used only if 0x14, Bit 7 is set to 1.
0 = Vsync is from the VSYNC input pin.
1 = Vsync is from the sync separator.
5
**0* ****
Vsync Polarity Override.
0 = The chip selects the input Vsync polarity.
1 = The polarity of the input Vsync is set by 0x14, Bit 4.
This applies to both Vsync0 and Vsync1.
4
***1 ****
Vsync input polarity: this bit is used only if 0x14, Bit 5 is set to 1.
0 = Active low input Vsync.
1 = Active high input Vsync.
3
**** 1***
Sets the polarity of the output Vsync signal.
0 = Active low output Vsync.
1 = Active high output Vsync.
2
**** *0**
0 = The Vsync filter is disabled.
1 = The Vsync filter is enabled.
This needs to be enabled when using the Hsync to Vsync
counter.
1
**** **0*
Enables the Vsync duration block. This is designed to be used
with the Vsync filter.
0 = Vsync output duration is unchanged.
1 = Vsync output duration is set by Register 0x15.
0x15
R/W
7:0
0000 1010
Vsync Duration
Sets the number of Hsyncs that Vsync out is active. This is only
used if 0x14, Bit 1 is set to 1.
0x16
R/W
7:0
0000 0000
Precoast
The number of Hsync periods to Coast prior to Vsync.
0x17
R/W
7:0
0000 0000
Postcoast
The number of Hsync periods to Coast after Vsync.
0x18
R/W
7
0*** ****
Coast and Clamp
Control
Coast Source.
Selects the source of the Coast signal.
0 = Using internal Coast generated from Vsync.
1 = Using external Coast signal from external Coast pin.