Datasheet

www.ti.com

CAPTURE TEST PATTERNS

ADS6424

ADS6423

ADS6422

SLAS532A – MAY 2007 – REVISED JUNE 2007

ADS642X outputs the bit clock (DCLK), positioned nearly at the center of the data transitions. It is recommended

to route the bit clock, frame clock and output data lines with minimum relative skew on the PCB. This ensures

sufficient setup/hold times for a reliable capture by the receiver.

The DESKEW is a 1010... or 0101... pattern output on the serial data lines that can be used to verify if the

receiver capture clock edge is positioned correctly. This may be useful in case there is some skew between

DCLK and serial data inside the receiver. Once deserialized, it is required to ensure that the parallel data is

aligned to the frame boundary. The SYNC test pattern can be used for this. For example, in the 1-wire interface,

the SYNC pattern is 6 '1's followed by 6 '0's (from MSB to LSB). This information can be used by the receiver

logic to shift the deserialized data until it matches the SYNC pattern.

In addition to DESKEW and SYNC, the ADS642X includes other test patterns to verify correctness of the capture

by the receiver such as all zeros, all ones and toggle. These patterns are output on all four channel data lines

simultaneously. Some patterns like custom and sync are affected by the type of interface selected, serialization

and bit order.

Table 25. Test Patterns

PATTERN DESCRIPTION

All zeros Outputs logic low.

All ones Outputs logic high.

Toggle Outputs toggle pattern – <D11 – D0> alternates between 101010101010 and 010101010101 every clock cycle.

Outputs a 12-bit custom pattern. The 12-bit custom pattern can be specified into two serial interface registers. In the

Custom

2-wire interface, each code is sent over the 2 wires depending on the serialization and bit order.

Sync Outputs a sync pattern.

Deskew Outputs deskew pattern. Either <D11 – D0> = 101010101010 or <D11-D0> = 010101010101 every clock cycle.

Table 26. SYNC Pattern

INTERFACE OPTION SERIALIZATION SYNC PATTERN ON EACH WIRE

12 X MSB-111111000000- LSB

1-Wire

14 X MSB-11111110000000- LSB

12 X MSB-111000- LSB

2-Wire

14 X MSB-1111000- LSB

Submit Documentation Feedback