AD9253

Data Sheet

Rev. B | Page 28 of 40

Table 11. 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

N/A

N/A

0001

Midscale short

1000 0000 0000 (12-bit)

1000 0000 0000 0000 (16-bit)

N/A

Yes

Offset binary

code shown

0010

+Full-scale short

1111 1111 1111 (12-bit)

1111 1111 1111 1100 (16-bit)

N/A

Yes

Offset binary

code shown

0011

−Full-scale short

0000 0000 0000 (12-bit)

0000 0000 0000 0000 (16-bit)

N/A

Yes

Offset binary

code shown

0100

Checkerboard

1010 1010 1010 (12-bit)

1010 1010 1010 1000 (16-bit)

0101 0101 0101 (12-bit)

0101 0101 0101 0100 (16-bit)

No

0101

N/A

N/A

Yes

PN23

ITU 0.150

0110

N/A

N/A

Yes

PN9

ITU 0.150

0111

One-/zero-word

toggle

1111 1111 1111 (12-bit)

111 1111 1111 1100 (16-bit)

0000 0000 0000 (12-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 (12-bit)

1010 1010 1010 1000 (16-bit)

N/A

No

1010

1× sync

0000 0011 1111 (12-bit)

0000 0001 1111 1100 (16-bit)

N/A

No

1011

One bit high

1000 0000 0000 (12-bit)

1000 0000 0000 0000 (16-bit)

N/A

No

Pattern

associated

with the

external pin

1100

Mixed frequency

1010 0011 0011 (12-bit)

1010 0001 1001 1100 (16-bit)

N/A

No

1

All test mode options except PN sequence short and PN sequence long can support 12-bit to 16-bit word lengths to verify data capture to the receiver.

When the SPI is used, the DCO phase can be adjusted in 60°

increments relative to one data cycle (30° relative to one DCO

cycle). This enables the user to refine system timing margins if

required. The default DCO± to output data edge timing, as

shown in Figure 2, is 180° relative to one data cycle (90° relative

to one DCO cycle).

A 12-bit serial stream can also be initiated from the SPI. This

allows the user to implement and test compatibility to lower

resolution systems. When changing the resolution to a 12-bit

serial stream, the data stream is shortened. See Figure 3 for the

12-bit example. However, in the default option with the serial

output number of bits at 16, the data stream stuffs two 0s at the

end of the 14-bit serial data.

In default mode, as shown in 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 to Table 11 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.

The PN sequence short pattern produces a pseudorandom bit

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

seed value is all 1s (see Table 12 for the initial values). The

output is a parallel representation of the serial PN9 sequence in

MSB-first format. The first output word is the first 14 bits of the

PN9 sequence in MSB aligned form.

The PN sequence long pattern produces a pseudorandom bit

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

seed value is all 1s (see Table 12 for the initial values) and the

AD9253 inverts the bit stream with relation to the ITU standard.

The output is a parallel representation of the serial PN23 sequence

in MSB-first format. The first output word is the first 14 bits of the

PN23 sequence in MSB aligned form