Data Sheet AD9888
Rev. C | Page 21 of 36
2-WIRE SERIAL REGISTER MAP
The AD9888 is initialized and controlled by a set of registers that determine the operating modes. An external controller is employed to
write and read the control registers through the two-line serial interface port.
Table 8. Control Register Map
Hex
Address
Read and
Write, or
Read Only Bits
Default
Value Register Name Function
0x00 RO [7:0] Chip revision An 8-bit register that represents the silicon revision level.
0x01
R/W
[7:0] 01101001 PLL divider MSB
MSBs (Bits[11:4]) of the PLL divider word. Larger values mean the PLL
operates at a faster rate. This register should be loaded first whenever a
change is needed to allow the PLL more time to lock.
1
0x02
R/W
[7:4] 1101**** PLL divider LSB LSBs of the PLL divider word.
1
0x03
R/W
[7:3] 01******
VCO range
select/charge
pump current
Bits[7:6]—VCO range. Selects VCO frequency range. See the Clock
Generation section.
**001***
Bits[5:3]—charge pump current. Varies the current that drives the low-
pass filter. See the Clock Generation section.
0x04
R/W
[7:3] 10000***
Clock Phase
adjust
ADC Clock phase adjustment. Larger values mean more delay.
(1 LSB = t/32)
0x05
R/W
[7:0] 00001000
Clamp
placement
Places the CLAMP signal an integer number of clock periods after the
trailing edge of the HSYNC signal.
0x06
R/W
[7:0] 00010100 Clamp duration Number of clock periods that the CLAMP signal is actively clamping.
0x07
R/W
[7:0] 00100000
HSYNC output
pulse width
Sets the number of pixel clocks that HSOUT remains active.
0x08
R/W
[7:0] 10000000 Red gain
Controls the ADC input range (contrast) of the red channel. Bigger
values result in less contrast.
0x09
R/W
[7:0] 10000000 Green gain Same function as the red gain bits, but for the green channel.
0x0A
R/W
[7:0] 10000000 Blue gain Same function as the red gain bits, but for the blue channel.
0x0B
R/W
[7:1] 1000000* Red offset
Controls dc offset (brightness) of the red channel. Bigger values
decrease brightness.
0x0C
R/W
[7:1] 1000000* Green offset Same function as the red offset bits, but for the green channel.
0x0D
R/W
[7:1] 1000000* Blue offset Same function as the red offset bits, but for the blue channel.
0x0E
R/W
[7:0] 0******* Sync control
Bit 7—HSYNC input polarity override. Logic 0 = polarity determined by
chip; Logic 1 = polarity set by Bit 6 in Register 0x0E.
*1******
Bit 6—HSYNC input polarity. Indicates to the PLL the polarity of the
incoming HSYNC signal. Logic 0 = active low; Logic 1 = active high.
**0*****
Bit 5—HSYNC output polarity. Logic 0 = logic high sync; Logic 1 = logic
low sync.
***0****
Bit 4—active HSYNC override. Logic 1 = the user can select the HSYNC
to be used via Bit 3; Logic 0 = the active interface is selected via Bit 6 in
Register 0x14.
****0***
Bit 3—active HSYNC select. Logic 0 = selects HSYNC as the active sync;
Logic 1 = selects sync-on-green as the active sync. Note that the
indicated HSYNC is used only if Bit 4 is set to Logic 1 or if both syncs are
active (Bit 1 and Bit 7 are set to Logic 1 in Register 0x14).
*****0** Bit 2—VSYNC output invert. Logic 0 = invert; Logic 1 = no invert.
******0*
Bit 1—active VSYNC override. Logic 1 = the user can select the VSYNC to
be used via Bit 0; Logic 0 = the active interface is selected via Bit 3 in
Register 0x14.
*******0
Bit 0—active VSYNC select. Logic 0 = selects raw VSYNC as the output
VSYNC; Logic 1 = selects sync separated VSYNC as the output VSYNC.
Note that the indicated VSYNC is used only if Bit 1 is set to Logic 1.
