
AD9980
Preliminary Technical Data
Rev. 0 | Page 24 of 44
Hexadecimal
Address
Read and
Write or
Read Only
Bits
Default
Value
Register
Name
Description
5
**1* ****
Coast Input Polarity.
This bit is used only if 0x18, Bit 6 is set to 1.
0 = Active low external Coast.
1 = Active high external Coast.
4
***0 ****
Clamp Source Select.
0 = Use the internal clamp generated from Hsync.
1 = Use the external clamp signal.
3
**** 0***
Red Clamp.
0 = Clamp the red channel to ground.
1 = Clamp the red channel to midscale.
2
**** *0**
Green Clamp.
0 = Clamp the green channel to ground.
1 = Clamp the green channel to midscale.
1
**** **0*
Blue Clamp.
0 = Clamp the blue channel to ground.
1 = Clamp the blue channel to midscale.
0
**** ***0
Must be set to 0 for proper operation.
0x19
R/W
7:0
0000 1000
Clamp
Placement
Places the clamp signal an integer of clock periods after the trailing
edge of the Hsync signal.
0x1A
R/W
7:0
0010 0000
Clamp
Duration
Number of clock periods that the clamp signal is actively clamping.
0x1B
R/W
7
0*** ****
Clamp and
Offset
External clamp polarity override.
0 = The chip selects the clamp polarity.
1 = The polarity of the clamp signal is set by 0x1B, Bit 6.
6
*1** ****
External Clamp Input Polarity. This bit is used only if 0x1B, Bit 7 is
set to 1.
0 = Active low external clamp.
1 = Active high external clamp.
5
**0* ****
0 = Auto-offset is disabled.
1 = Auto-offset is enabled (offsets become the desired clamp
code).
4:3
***1 1***
This selects how often the auto-offset circuit operates. 00 = every
clamp; 01 = 16 clamps; 10 = every 64 clamps; 11 = every Vsync.
2:0
**** *011
Must be written to default (011) for proper operation.
0x1C
R/W
7:0
1111 1111
TestReg0
Must be set to 0xFF for proper operation.
0x1D
R/W
7:3
0111 1***
SOG Control
SOG slicer threshold. Sets the voltage level of the SOG slicer’s
comparator.
2
**** *0**
SOGOUT Polarity.
Sets the polarity of the signal on the SOGOUT pin.
0 = Active low SOGOUT.
1 = Active high SOGOUT.
1:0
**** **00
SOGOUT Select.
00 = Raw SOG from sync slicer (SOG0 or SOG1).
01 = Raw Hsync (Hsync0 or Hsync1).
10 = Regenerated sync from sync filter.
11 = Filtered sync from sync filter.
0x1E
R/W
7
*** ****
Power
Channel Select Override.
0 = The chip determines which input channels to use.
1 = The input channel selection is determined by 0x1E, Bit 6.
6
*0** ****
Channel Select.
Input channel select: this is used only if 0x1E, Bit 7 is set to 1, or if
syncs are present on both channels.
0 = Channel 0 syncs and data are selected.
1 = Channel 1 syncs and data are selected.