
Data Sheet
AD9653
Rev. 0 | Page 29 of 40
Two output clocks are provided to assist in capturing data from
the
AD9653. The DCO is used to clock the output data and is
equal to four times the sample clock (CLK) rate for the default
mode of operation. Data is clocked out of the
AD9653 and must
be captured on the rising and falling edges of the DCO that
supports double data rate (DDR) capturing. The FCO is used to
signal the start of a new output byte and is equal to the sample
for more information.
When the SPI is used, the DCO phase can be adjusted in 60°
increments relative to the data edge. This enables the user to
refine system timing margins if required. The default DCO+
and DCO timing, as shown i
n Figure 2, is 90° relative to the
output data edge.
In default mode, as shown i
n Figure 2, the MSB is first in the
data output serial stream. This can be inverted so that the LSB
is first in the data output serial stream by using the SPI.
There are 12 digital output test pattern options available that
can be initiated through the SPI. This is a useful feature when
validating receiver capture and timing. Refer t
o Table 13 for the
output bit sequencing options available. Some test patterns have
two serial sequential words and can be alternated in various
ways, depending on the test pattern chosen. Note that some
patterns do not adhere to the data format select option. In
addition, custom user-defined test patterns can be assigned in
the 0x19, 0x1A, 0x1B, and 0x1C register addresses.
Table 12. Digital Output Coding
Input (V)
Condition (V)
Offset Binary Output Mode
Twos Complement Mode
VIN+ VIN
<VREF 0.5 LSB
0000 0000 0000 0000
1000 0000 0000 0000
VIN+ VIN
VREF
0000 0000 0000 0000
1000 0000 0000 0000
VIN+ VIN
0 V
1000 0000 0000 0000
0000 0000 0000 0000
VIN+ VIN
+VREF 1.0 LSB
1111 1111 1111 1111
0111 1111 1111 1111
VIN+ VIN
>+VREF 0.5 LSB
1111 1111 1111 1111
0111 1111 1111 1111
Table 13. Flexible Output Test Modes
Output Test
Mode Bit
Sequence
Pattern Name
Digital Output Word 1
Digital Output Word 2
Subject to
Data Format
Select
Notes
0000
Off (default)
N/A
0001
Midscale short
1000 0000 0000 0000 (16-bit)
N/A
Yes
Offset binary
code shown
0010
+Full-scale short
0000 0000 0000 0000 (16-bit)
N/A
Yes
Offset binary
code shown
0011
Full-scale short
0000 0000 0000 0000 (16-bit)
N/A
Yes
Offset binary
code shown
0100
Checkerboard
1010 1010 1010 1010 (16-bit)
0101 0101 0101 0100 (16-bit)
No
0101
PN sequence long
N/A
Yes
PN23
ITU 0.150
X23 + X18 + 1
0110
PN sequence short
N/A
Yes
PN9
ITU 0.150
X9 + X5 + 1
0111
One-/zero-word
toggle
111 1111 1111 1100 (16-bit)
0000 0000 0000 0000 (16-bit)
No
1000
User input
Register 0x19 to Register 0x1A
Register 0x1B to Register 0x1C
No
1001
1-/0-bit toggle
1010 1010 1010 1000 (16-bit)
N/A
No
1010
1× sync
0000 0001 1111 1100 (16-bit)
N/A
No
1011
One bit high
1000 0000 0000 0000 (16-bit)
N/A
No
Pattern
associated with
the external pin
1100
Mixed frequency
1010 0001 1001 1100 (16-bit)
N/A
No