AD9671EBZ datasheet(31/61 Pages) AD

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AD9671

Data Sheet

Rev. A| Page 30 of 60

Table 14. JESD204B Parameters

Parameter

Description

AD9671 Value

Samples transmitted per single converter per frame cycle

Number of converters per converter device

8 with demodulator/decimator disabled, 16 with

demodulator/decimator enabled

Number of lanes per converter device

1, 2, or 4

Converter resolution

12, 14, or 16

N’

Total number of bits per sample

Number of control words per frame clock cycle per

converter device

Number of control bits per conversion sample

Number of frames per multiframe

Configurable on the AD9671

High density mode

Octets per frame

4, 8, 16, or 32 (dependent on L = 4, 2, or 1, respectively)

Control bit

Tail bit

Available on the AD9671

SCR

Scrambler enable/disable

Configurable on the AD9671

FCHK

Checksum for the JESD204B parameters

Automatically calculated and stored in the register map

OUTPUT

SAMPLES

FROM CHANNEL

TRANSPORT

LAYER

DATA LINK

LAYER

PHYSICAL

LAYER

SCRAMBLER

SERIALIZER

FRAME

CONSTRUCTION

8B/10B

ENCODER

SAMPLE

CONSTRUCTION

LANE

ALIGNMENT

CHARACTER

GENERATION

Figure 45. AD9671 Transmit Link Simplified Block Diagram

Figure 45 shows a simplified block diagram of the AD9671

JESD204B link. By default, the AD9671 is configured to use

eight channels and four lanes. Channel A and Channel B data

is output to SERDOUT1±, Channel C and Channel D data is

output to SERDOUT2±, Channel E and Channel F data is

output to SERDOUT3±, and Channel G and Channel H data

is output to SERDOUT4±. The AD9671 allows other configura-

tions such as combining the outputs of the eight channels onto a

single lane.

By default in the AD9671, the 14-bit converter word from each

converter is broken into two octets (eight bits of data). Bit 0

(MSB) through Bit 7 are in the first octet. The second octet

contains Bit 8 through Bit 13 (LSB) and two tail bits. The tail

bits can be configured as zeros or a pseudorandom number

sequence.

The two resulting octets can be scrambled. Scrambling is optional

but is available to avoid spectral peaks when transmitting similar

digital data patterns. The scrambler uses a self synchronizing

polynomial-based algorithm defined by the equation: 1 + x14 +

x15. The descrambler in the receiver must be a self synchronizing

version of the scrambler polynomial.

The two octets are then encoded with an 8B/10B encoder. The

8B/10B encoder works by taking eight bits of data (an octet) and

encoding them into a 10-bit symbol. Figure 46 shows how the

14-bit data is taken from the ADC, the tail bits are added, the two

octets are scrambled, and how the octets are encoded into two

10-bit symbols. Figure 46 illustrates the default data format.

At the data link layer, in addition to the 8B/10B encoding, the

character replacement allows the receiver to monitor frame

alignment. The character replacement process occurs on the

frame and multiframe boundaries, and implementation depends

on which boundary is occurring and if scrambling is enabled.

If scrambling is disabled, the following applies. If the last

scrambled octet of the last frame of the multiframe equals the

last octet of the previous frame, the transmitter replaces the last

octet with the control character /A/ = /K28.3/. On other frames

within the multiframe, if the last octet in the frame equals the

last octet of the previous frame, the transmitter replaces the last

octet with the control character /F/ = /K28.7/.

If scrambling is enabled, the following applies. If the last octet of

the last frame of the multiframe equals 0x7C, the transmitter

replaces the last octet with the control character /A/ = /K28.3/.

On other frames within the multiframe, if the last octet equals

0xFC, the transmitter replaces the last octet with the control

character /F/ = /K28.7/.

Refer to JEDEC Standard JESD204B (July 2011) for additional

information about the JESD204B interface. Section 5.1

describes the transport layer and data format details, and

Section 5.2 describes scrambling and descrambling.

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