
AD9974
Rev. A | Page 43 of 52
Address
Data Bit
Content
Default
Value
Update
Name
Description
0x0C
[27:0]
0
VD
TESTMODE
Test Operation Only. Set to 0 if this register is accessed.
0x0D
[0]
0
VD
CLIDIVIDE
CLI Divide.
1 = divide CLI input frequency by 2.
[3:1]
0
TESTMODE
Test Operation Only. Set to 0.
[27:4]
Unused
Set unused bits to 0.
0x0E
[27:0]
SCK
Unused
Set unused register to 0 if accessed.
0x0F
[27:0]
SCK
Unused
Set unused register to 0 if accessed.
Table 23. Miscellaneous Registers
Address
Data Bit
Content
Default
Value
Update
Name
Description
0x10
[0]
0
SCK
SW_RST
Software Reset. Bit self-clears to 0 when a reset occurs.
1 = reset Address 0x00 to Address 0xFF to default values.
[27:1]
Unused
Set unused bits to 0.
0x11
[0]
0
VD
OUT_CONTROL
Output Control.
0 = make all outputs dc inactive.
1 = enable outputs at next VD edge.
[27:1]
Unused
Set unused bits to 0.
0x12
[1:0]
0
SCK
TESTMODE
Test Operation Only. Set to 0.
[27:2]
Unused
Set unused bits to 0.
0x13
[0]
0
SCK
TESTMODE
Test Operation Only. Set to 0.
[27:1]
Unused
Set unused bits to 0.
0x14
[0]
0
SCK
TGCORE_RST
Timing Core Reset Bar.
0 = hold in reset.
1 = resume operation.
[27:1]
Unused
Set unused bits to 0.
0x15
[0]
0
SCK
CLI_BIAS
0 = disable bias (CLI input is dc-coupled).
1 = enable bias (CLI input is ac-coupled).
[27:1]
Unused
Set unused bits to 0.
0x16
[0]
0
SCK
TESTMODE
Test Operation Only. Set to 0.
[27:1]
Unused
Set unused bits to 0.
0x17
[12:0]
0
SCK
UPDATE
Serial Interface Update Line. Sets the line (HD) within the field to
update the VD-updated registers. Disabled when PREVENTUP = 1.
[13]
0
PREVENTUP
Prevents normal update of VD-updated registers.
0 = normal update at VD.
1 = prevent update of VD-updated registers.
[27:14]
Unused
Set unused bits to 0.
0x18
[27:0]
0
TESTMODE
Test Operation Only. Set to 0 if this register is accessed.
0x19
[27:0]
0
TESTMODE
Test Operation Only. Set to 0 if this register is accessed.
0x1A to
0x1F
[27:0]
Unused
Set unused bits to 0.
Table 24. VD/HD Registers
Address
Data Bit
Content
Default
Value
Update
Name
Description
0x20
[0]
0
SCK
TESTMODE
Test Operation Only. Set to 0.
[27:1]
Unused
Set unused bits to 0.
0x21
[0]
0
SCK
VDHDPOL
VD/HD Active Polarity.
0 = active low.
1 = active high.
[2:1]
0
TESTMODE
Test Operation Only. Set to 0.
[27:3]
Unused
Set unused bits to 0.
0x22
[27:0]
0
TESTMODE
Test Operation Only. Set to 0 if this register is accessed.