AD6676EBZ datasheet(48/90 Pages) AD

48 / 90 page

AD6676

Data Sheet

Rev. A | Page 48 of 90

For scrambled data, any 0xFC character at the end of a frame is

replaced by an /F/ and any 0x7C character at the end of a

multiframe is replaced with an /A/. The JESD204B receiver

checks for /F/ and /A/ characters in the received data stream

and verifies that they only occur in the expected locations. If an

unexpected /F/ or /A/ character is found, the receiver uses

dynamic realignment or asserts the SYNCINB± signal for more

than four frames to initiate a resynchronization. For

unscrambled data, if the final character of two subsequent

frames is equal, the second character is replaced with an /F/ if it

is at the end of a frame, and an /A/ if it is at the end of a

multiframe.

Insertion of alignment characters may be modified using SPI.

The frame alignment character insertion is enabled by default.

More information on the link controls is available in the SPI

8-Bit/10-Bit Encoder

The 8-bit/10-bit encoder converts 8-bit octets into 10-bit

symbols and inserts control characters into the stream when

needed. The control characters used in JESD204B are shown in

Table 18. The 8-bit/10-bit encoding ensures that the signal is dc

balanced by using the same number of ones and zeroes across

multiple symbols. Note that the 8-bit/10-bit interface has an

invert option available in Register 0x1E4 that has the same

effect of swapping the differential output data pins.

K K R D

D A R Q C

C D

D A R D

D A D

START OF

ILAS

START OF LINK

CONFIGURATION DATA

END OF

MULTIFRAME

START OF

USER DATA

Figure 121. Initial Lane Alignment Sequence

Table 18. Control Characters used in JESD204B Including Running Disparity Values

Abbreviation

Control Symbol

8-Bit Value

10-Bit Value (RD = −1)

10-Bit Value (RD = +1)

Description

/R/

K28.0

000 11100

001111 0100

110000 1011

Start of multiframe

/A/

K28.3

011 11100

001111 0011

110000 1100

Lane alignment

/Q/

K28.4

100 11100

001111 0010

110000 1101

Start of link configuration data

/K/

K28.5

101 11100

001111 1010

110000 0101

Group synchronization

/F/

K28.7

111 11100

001111 1000

110000 0111

Frame alignment

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