AD9212
Data Sheet
Rev. E | Page 28 of 56
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
in Figure 2, is 90° relative to the
output data edge.
An 8-, 12-, and 14-bit serial stream can also be initiated from the
SPI. This allows the user to implement different serial stream to
test the device’s compatibility with lower and higher resolution
systems. When changing the resolution to a 12-bit serial stream,
the data stream is lengthened. S
ee Figure 3 for the 12-bit example.
However, when using the 12-bit option, the data stream stuffs
two 0s at the end of the 10-bit serial data.
When the SPI is used, all data outputs can be inverted from
their nominal state. This is not to be confused with inverting
the serial stream to an LSB-first mode. In default mode, as
shown
in Figure 2, the MSB is first in the data output serial
stream. However, this can be inverted so that the LSB is first in
the data output serial stream (see
Figure 4).
There are 12 digital output test pattern options available that
can be initiated through the SPI. This feature is useful when
validating receiver capture and timing. Refer t
o Table 9 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, customer user-defined test patterns can be assigned in
the 0x19, 0x1A, 0x1B, and 0x1C register addresses. All test mode
options except PN sequence short and PN sequence long can
support 8- to 14-bit word lengths in order to verify data capture
to the receiver.
The PN sequence short pattern produces a pseudorandom bit
sequence that repeats itself every 29 1 or 511 bits. A description
of the PN sequence and how it is generated can be found in
Section 5.1 of the ITU-T 0.150 (05/96) standard. The only
difference is that the starting value must be a specific value
The PN sequence long pattern produces a pseudorandom bit
sequence that repeats itself every 223 1 or 8,388,607 bits. A
description of the PN sequence and how it is generated can be
found in Section 5.6 of the ITU-T 0.150 (05/96) standard. The
only differences are that the starting value must be a specific
value instead of all 1s (se
e Table 10 for the initial values) and the
AD9212 inverts the bit stream with relation to the ITU standard.
Table 10. PN Sequence
Sequence
Initial
Value
First Three Output Samples
(MSB First)
PN Sequence Short
0x0df
0xdf9, 0x353, 0x301
PN Sequence Long
0x29b80a
0x591, 0xfd7, 0xa3
SDIO/ODM Pin
The SDIO/ODM pin is for use in applications that do not require
SPI mode operation. This pin can enable a low power, reduced
signal option (similar to the IEEE 1596.3 reduced range link
output standard) if it and the CSB pin are tied to AVDD during
device power-up. This option should only be used when the
digital output trace lengths are less than 2 inches from the LVDS
receiver. When this option is used, the FCO, DCO, and outputs
function normally, but the LVDS signal swing of all channels is
reduced from 350 mV p-p to 200 mV p-p, allowing the user to
further reduce the power on the DRVDD supply.
For applications where this pin is not used, it should be tied low.
In this case, the device pin can be left open, and the 30 kΩ internal
pull-down resistor pulls this pin low. This pin is only 1.8 V tolerant.
If applications require this pin to be driven from a 3.3 V logic level,
insert a 1 kΩ resistor in series with this pin to limit the current.
Table 11. Output Driver Mode Pin Settings
Selected ODM
ODM Voltage
Resulting
Output Standard
Resulting
FCO and DCO
Normal
Operation
AGND
(10 kΩ pull-
down resistor)
ANSI-644
(default)
ANSI-644
(default)
ODM
AVDD
Low power,
reduced signal
option
Low power,
reduced signal
option
SCLK/DTP Pin
The SCLK/DTP pin is for use in applications that do not require
SPI mode operation. This pin can enable a single digital test pattern
if it and the CSB pin are held high during device power-up. When
the SCLK/DTP is tied to AVDD, the ADC channel outputs shift
out the following pattern: 10 0000 0000. The FCO and DCO
function normally while all channels shift out the repeatable
test pattern. This pattern allows the user to perform timing
alignment adjustments among the FCO, DCO, and output data.
For normal operation, this pin should be tied to AGND through
a 10 kΩ resistor. This pin is both 1.8 V and 3.3 V tolerant.
Table 12. Digital Test Pattern Pin Settings
Selected DTP
DTP Voltage
Resulting
D + x and D x
Resulting
FCO and DCO
Normal
Operation
AGND
(10 kΩ pull-
down resistor)
Normal
operation
Normal operation
DTP
AVDD
10 0000 0000
Normal operation
Additional and custom test patterns can also be observed when
for information about the options available.