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ADC12J4000 JESD204B

arnaud carer
Prodigy 100 points
Other Parts Discussed in Thread: ADC12J4000EVM

HI,

I use ADC12J4000EVM with an ZC706 board from Xilinx.

When à set the ramp test mode I received correct data but when I configure the ADC in normal mode or short transport test mode with ADC12J4000EVM  I received aperiodique K characters on the serial line.

I use ADC with DDC OFF, 4Gsps, scrambler off.

Do you have an idee where my problem come from?

bad ADC configuration, bad synchronisation, pre-emphasys setting....

regards,

Arnaud

  • 0
    TI__Mastermind 44680 points

    Hi Arnaud

    To comply with the JESD204B standard, the ADC will sometimes insert alignment (K characters) into the output data stream. The character insertion follows the rules shown in JESD204B Sections 5.3.3.4.1, 5.3.3.4.2, 5.3.3.4.3 and also covered in Section 8.1. The insertion is done at the transmitter and the receiver is expected to reverse the process, replacing the K character with the data value that should have been there.

    When the octet ramp test pattern is enabled, the alignment character insertion is disabled.This is also true for the repeated ILA, modified RPAT, PRBSn, D21.5 and K28.5 test patterns.

    Alignment character insertion is enabled in the short transport test pattern, long transport test pattern, and normal data modes.

    Please confirm with your FPGA vendor that your JESD204B receive IP is properly configured to accept these characters, and perform the expected operations as required by the standard.

    Best regards,

    Jim B

  • 0 in reply to Jim Brinkhurst1
    Prodigy 100 points
    Thank you very much for your response

    My sample rate is 4 Gsps for 12 bits I have 8 lane so I have to transmit 0,5Gsps per lanes so 6 Gbits
    To transmit 5 samples (60 bits) I need 64 bits so I must transmit 6*64/60= 6,4 Gbits
    With 8b10b the line rate is 6,4Gbits*1,25=8Gbits that is equal to my line rate.

    So to transmit the alignement characters I understand that my line rate need to be greater than 8Gbit/s?

    Best regards
  • 0 in reply to arnaud carer
    TI__Mastermind 44680 points

    Hi Arnaud

    The alignment characters are inserted in place of normal data octets. So the amount of data does not change and the line rate stays the same.

    Here is one example of how the character replacement is specified in the standard.

    "5.3.3.4.2Character replacement without scrambling

    If both sides of the lane support lane synchronization, character replacement in the transmitter and receiver during transmission of data from the transport layer (see 5.1) shall be as follows:

     • When the last octet in the current frame, not coinciding with the end of a multiframe, equals the last octet in the previous frame, the transmitter shall replace the current last octet and encode it as control character /F/= /K28.7/. However, if an alignment character was already transmitted in the previous frame, the original octet shall be encoded.

     • When the last octet in the current frame at the end of a multiframe equals the last octet in the previous frame, the transmitter shall replace the current last octet and encode it as control character /A/= /K28.3/, even if a control character was already transmitted in the previous frame.

     • Upon receiving an /F/ or /A/ symbol, the receiver shall replace it with the value of the octet decoded or used at the same position in the previous frame.

     If at least one side of the lane does not support lane synchronization (i.e., for NMCDA-SL class devices, see clause 9), character replacement in the transmitter and receiver during transmission of data from the transport layer (see 5.1) shall be as follows:

     • When the last octet in the current frame equals the last octet in the previous frame, the transmitter shall replace the current last octet with /K28.7/. However, if a /K28.7/ symbol was already transmitted in the previous frame, the actual octet shall be transmitted

     • Upon receiving a /K28.7/ symbol, the receiver shall replace it with the value of the data octet decoded at the same position in the previous frame

     NOTE The "last octet in a frame or multiframe" means the last octet in the frame or multiframe transmitted on a given lane, hence the character replacement functions in each lane are independent."

    "

    I hope this makes it more clear.

    Best regards,

    Jim B