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DS250DF230: Calibration Clock

K.Yaita
Guru 29720 points
Part Number: DS250DF230
Other Parts Discussed in Thread: , SIGCONARCHITECT

Hi Team,

My customer considers to use DS250DF230 under the following data rates.
・25.78125 Gbps
・10.3125 Gbps
・9.8304 Gbps
・4.9152 Gbps
・2.4576 Gbps

1)
I believe DS250DF230 doesn't support 2.4576 Gbps data rate.
Is my understanding correct?

2)
Is it possible to use calibration clock both 25MHz and 30.72MHz for data rates above?
I saw Table 25 and Table 27 in Programmer's Guide however I couldn't judge if these data rates are supported or not.

Best Regards,
Yaita

  • 0
    TI__Mastermind 19235 points

    Hi,

    The DS250DF230 does not support 2.4576G in retimed mode, but may be operated in this rate after configuration to CDR bypass mode.

    My recommendation would be to use 30.72MHz clock in your case. Using 30.72MHz clock allows all of your data rates to be supported via the retimer Standard Rate Mode (i.e. you only need to write to 0x2F to set the CDR rate)

    Table. DS250DF230 Standard Rate Modes Configurable from Reg_0x2F (1)

    STANDARD RATE SETTING

    REG_0x2F VALUE [HEX]

    REG_0x2F WRITE MASK [HEX]

    RECOVERED CLOCK FREQUENCY [MHZ]

    12.16512 Gbps

    00

    F0

    30.72

    9.83040 Gbps

    10

    30.72

    10.13760 Gbps

    20

    30.72

    24.33024 Gbps

    30

    30.72

    4.91520 Gbps

    40

    30.72

    25.78125 Gbps(Default)

    50

    32.2265625

    10.31250 Gbps

    60

    32.2265625

    25.78125 Gbps

    32.2265625

    10.31250 Gbps

    70

    32.2265625

    6.14400 Gbps

    80

    30.72

    (1) This table is valid only when the calibration clock is 30.72-MHZ

  • 0 in reply to Rodrigo Natal
    Guru 29720 points

    Hi Rodrigo-san,

    Thank you for your kind support. I would like to ask additional questions.

    3)
    The table you attached is identical with Table 6 of DS250DF230 datasheet and it shows "This table is valid only when the calibration clock is 30.72 MHz".
    Is there same table that is valid when the calibration clock is 25MHz?
     
    4)
    Which data rate that can't be supported when the calibration clock is 25MHz?
    ・25.78125 Gbps
    ・10.3125 Gbps
    ・9.8304 Gbps
    ・4.9152 Gbps

    5)
    Table 27 of Programmer's Guide doesn't show register settings for DATA RATE=4.9152 Gbps.
    Could you tell me the register setting for DATA RATE=4.9152 Gbps?

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    Guru 29720 points

    May I have your reply?

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Mastermind 19235 points

    The table you attached is identical with Table 6 of DS250DF230 datasheet and it shows "This table is valid only when the calibration clock is 30.72 MHz".Is there same table that is valid when the calibration clock is 25MHz?

     

    • Yes. see below table from programming guide.

    Table. Register Settings for Common Data Rates using 25-MHz Calibration Clock

    DATA RATE

    REG_0x60 VALUE [HEX]

    REG_0x61 VALUE [HEX]

    REG_0x62 VALUE [HEX]

    REG_0x63 VALUE [HEX]

    REG_0x18[6:4] VALUE [HEX]

    25.78125 Gbps (1)

    74

    C0

    74

    C0

    0

    25.0 Gbps (1)

    80

    BE

    80

    BE

    0

    20.625 Gbps

    90

    B3

    90

    B3

    0

    12.5 Gbps (1)

    80

    BE

    80

    BE

    1

    10.3125 Gbps (1)

    90

    B3

    90

    B3

    1


    4)
    Which data rate that can't be supported when the calibration clock is 25MHz?
    ・25.78125 Gbps
    ・10.3125 Gbps
    ・9.8304 Gbps
    ・4.9152 Gbps

    • The first three rates are indeed supported in retimed mode when clock is 25MHz. See my table above for 25.78125G and 10.3125G. For 9.8304G the user may configure the CDR rate via manual mode using channel registers 0x60 thru 0x64.
    • The user may run retimer at 4.9152Gbps after setting the channel to CDR bypass mode 

    5)
    Table 27 of Programmer's Guide doesn't show register settings for DATA RATE=4.9152 Gbps.
    Could you tell me the register setting for DATA RATE=4.9152 Gbps?

    • The retimer cannot operate at 4.9152Gbps in retimed mode. The user should instead set the retimer channel to CDR bypass mode. See below table from the retimer programming guide

    Table . Select Output Mode When CDR is Not Locked

    　

    STEP

    SHARED/ CHANNEL REGISTER SET

    OPERATION

    REGISTER ADDRESS [HEX]

    REGISTER VALUE [HEX]

    WRITE MASK [HEX]

    COMMENT

    1

    Channel

    Write

    1E

    E0

    E0

    PFD_SEL_DATA_PRELCK=3' b111: Mute (default)

    Note: Reg_0x09[5] must be 0, which is the default.

    00

    E0

    PFD_SEL_DATA_PRELCK=3' b000: Raw, un-retimed data Note: Reg_0x09[5] must be 0, which is the default.

    Below are the setting to configure the retimer for 9.8304Gbps retimed mode

    0x09 = 0x04

    0x18 = 0x10

    0x60 = 0x26

    0x61 = 0xB1

    0x62 = 0x26

    0x63 = 0xB1

    0x64 = 0xFF

    Regards,

    Rodrigo Natal

    HSSC Applications Engineer

  • 0 in reply to Rodrigo Natal
    Guru 29720 points

    Hi Rodrigo-san,

    Thank you for your support.

    You refered DS250DF230 cannot operate at 4.9152Gbps in retimed mode regardless of calibration clock is 25MHz or 30.72MHz.
    Is it true?
    I doubt it because I believe internal VCO range is 19.6~25.8Gbps and 4.9~6.45Gbps can be supported when divide-by-4.



    Why DS250DF230 cannot operate at 4.9152Gbps in retimed mode?

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    Guru 29720 points

    Hi,

    May I have your comments?

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Mastermind 19235 points

    Hi Yaita, my mistake. You are correct regarding 4.91Gbps retimed mode operation.

    Regards,

    Rodrigo

  • 0 in reply to Rodrigo Natal
    Guru 29720 points

    Hi Rodrigo-san,

    Thank you for your reply.

    I believe 4.9152Gbps retimed mode operation can be achieved by Manual Configuration under 25MHz calibration clock although Table 25 of programmer's guide doesn't show 4.9152Gbps.
    Is my understanding correct?
    I would like to confirm just in case..

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Mastermind 19235 points

    Yes, confirming your understanding is correct.

  • 0 in reply to Rodrigo Natal
    Guru 29720 points

    Rodrigo-san,

    My customer is using DS250DF230EVM and set 4.9152Gbps retimed mode operation by Manual Configuration under 25MHz calibration clock, however CDR Lock couldn't be achieved.
    He judged CDR Lock by Device Status in SigConArchitect.
    Below are the register setting.
    -------------------------------------
    REG_0x09= 0x04
    REG_0x18= 0x20
    REG_0x60 (REG_0x62)= 0x93
    REG_0x61 (REG_0x63)= 0x98
    REG_0x64= 0xFF
    -------------------------------------
    I believe the setting is correct. Do you know why CDR Lock couldn't be achieved?

    He also confirmed Standard Data Rate Setting (REG_0x2F= 0x40: 4.9152Gbps) under 30.72MHz calibration clock, CDR Lock was achieved.

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Mastermind 19235 points

    Hi Yaita,

    The settings in your email are not right. See below the correct settings. I checked in the lab and confirmed that i'm able to lock to 4.9152Gbps input signal with these settings while implementing 25MHz calibration clock.

     -------------------------------------
    REG_0x09= 0x04
    REG_0x18= 0x20
    REG_0x60 (REG_0x62)= 0x26
    REG_0x61 (REG_0x63)= 0xB1
    REG_0x64= 0xFF

    Regards,

    Rodrigo

  • 0 in reply to Rodrigo Natal
    Guru 29720 points

    Hi Rodrigo-san,

    I really appreciate for your kind support.

    If your setting is correct, it seems the following calculation formula in programmer's guide is wrong.
    (page 23)
    REG_0x60_val = Floor{(DataRate * 1024) / (32 * 25E6)} & 0x00FF, For DataRate ≤ 13E9 bps (7)
    REG_0x61_val = Floor{(DataRate * 1024) / (32 * 25E6)} & 0xFF00 >> 8 | 0x80, For DataRate ≤ 13E9 bps (9)

    We should use 16 instead of 32 which is written above.
    I believe 16 should be used if using divide-by-4 (REG_0x18=0x20).
    Is my understanding correct?

    If my understanding correct, could you please update the programmer's guide?

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Mastermind 19235 points

    Hi,

    there is no issue with our calculation. I used the full data rate of 19.64G (i.e. 4 x 4.91G) for the calculation.

    Thanks,

    Rodrigo

  • 0 in reply to Rodrigo Natal
    Guru 29720 points

    Hi Rodrigo-san,

    It seems there is lack of my explanation.

    Programmer's guide (page 23 7.7.1 25-MHz Calibration Clock) shows that For DataRate > 13E9 bps we should use calculation formula (6) and (8), for DataRate ≤ 13E9 bps we should use (7) and (9).
    However if DataRate is 4.9152Gbps, the calcuration values that are calcurated from (7) and (9) aren't correct as you refered.
    So I would like to know the correct calcuration formula for DataRate=4.9152Gbps and request updating programmer's guide.

    If you have unclear, please let me know.

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Mastermind 19235 points

    Hi,

    For the manual data rate configuration equation per the programming guide, the factor in the denominator must be adjusted based on the data rate:

    • The factor is 64 for 19.66G
    • The factor is 32 for 9.83G
    • The factor is 16 for 4.915G

    Regards,

     Rodrigo Natal

  • 0 in reply to Rodrigo Natal
    Guru 29720 points

    Hi Rodrigo-san,

    Thank you for your answer.
    I think programmer's guide doesn't include the content you referred.
    Could you update programmer's guide?

    Best Regards,
    Yaita