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AD9880
Rev. 0 | Page 44 of 64
0x23
7-0
Hsync Duration
An 8 bit register that sets the duration of the Hsync
output pulse. The leading edge of the Hsync output is
triggered by the internally generated, phase-adjusted
PLL feedback clock. The AD9880 then counts a
number of pixel clocks equal to the value in this
register. This triggers the trailing edge of the Hsync
output, which is also phase-adjusted. The power-up
default is 32.
0x24
7
Hsync Output Polarity
This bit sets the polarity of the Hsync output. Setting
this bit to 0 sets the Hsync output to active low. Setting
this bit to 1 sets the Hsync output to active high.
Power-up default setting is 1.
Table 41. Hsync Output Polarity Settings
Hsync Output Polarity Bit
Result
0
Hsync output polarity negative
1
Hsync output polarity positive
0x24
6
Vsync Output Polarity
This bit sets the polarity of the Vsync output (both
DVI and analog). Setting this bit to 0 sets the Vsync
output to active low. Setting this bit to 1 sets the Vsync
output to active high. Power-up default is 1.
Table 42. Vsync Output Polarity Settings
Vsync Output Polarity Bit
Result
0
Vsync output polarity is negative
1
Vsync output polarity is positive
0x24
5
Display Enable Output Polarity
This bit sets the polarity of the display enable (DE) for
both DVI and analog.
Table 43. DE Output Polarity Settings
DE Output Polarity Bit
Result
0
DE output polarity is negative
1
DE output polarity is positive
The power-up default is 1.
0x24
4
Field Output Polarity
This bit sets the polarity of the field output signal on
Pin 21. The power-up default setting is 1.
Table 44. Field Output Polarity
Select
Result
0
Active low = even field; active high = odd field
1
Active low = odd field; active high = even field
Output field polarity (both DVI and analog)
0 = active low out
1 = active high out
The power-up default is 1.
0x24
3
SOG Output Polarity
This bit sets the polarity of the SOGOUT signal
(analog only).
Table 45. SOGOUT Polarity Settings
SOGOUT
Result
0
Active low
1
Active high
The power-up default setting is 1.
0x24
2-1
SOG Output Select
These register bits control the output on the SOGOUT
pin. Options are the raw SOG from the slicer (this is
the unprocessed SOG signal produced from the sync
slicer), the raw Hsync, the regenerated sync from the
sync filter, which can generate missing syncs because
of coasting or drop-out, or the filtered sync that
excludes extraneous syncs not occurring within the
sync filter window.
Table 46. SOGOUT Polarity Settings
SOGOUT Select
Function
00
Raw SOG from sync slicer (SOG0 or SOG1)
01
Raw Hsync (Hsync0 or Hsync1)
10
Regenerated sync from sync filter
11
Hsync to PLL
The power-up default setting is 11.
0x24 0
Output Clock Invert
This bit allows inversion of the output clock as
specified by Register 0x25, Bits 7 to 6. The power-up
default setting is 0.
Table 47. Output Clock Invert
Select
Result
0
Noninverted clock
1
Inverted clock
0x25
7-6
Output Clock Select
These bits select the clock output on the DATACLK
pin. They include 1/2× clock, a 2× clock, a 90° phase
shifted clock or the normal pixel clock. The power-up
default setting is 01.