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DS110DF410 - PRBS Generator

Kawai
Guru 19785 points

Other Parts Discussed in Thread: DS100DF410, DS110DF410, DS125DF410

Please help us how to use the PRBS Generator at Free run (No input signal).

We asked customer to program registers in the following steps, but the device did not output  PRBS pattern.

Q1)
What is the correct programming steps and value for the registers?

------------------------------------------------------------------------------------------------
       Adr    Data
  1) 0x1E  0xF1                     // Enable PRBS Generator digital circuit
  2) 0x30  8'b0000 00xx      // Reset PRBS CLK, Select PRBS Pattern (xx)
  3) 0x14  0x80                     // Force Signal Detect
  4) 0x09  0x08                     // Disable Charge pump for PLL
  5) 0x1B  8'bxxxx xx00        // Disable Charge pump for PLL
  6) 0x09  0x0C                    // Enable VCO Divider Override
  7) 0x18  0x00                    // VCO Divider Ratio (=1)
  8) 0x09  0x8C                    // VCO CAPDAC Override
  9) 0x08  0x0C                    // VCO CAP Count
10) 0x09  0xCC                  // Enable VCO LPF DAC
11) 0x1F  0x52                    // LPF DAC Output
12) 0x30  8'b000010xx      // Load PRBS CLK
13) 0x0D  0x20                   // Enable PRBS Generator
14) 0x09  0xEC                  // MUX override
15) 0x1E  0x91                  // Select PRBS Generator(MUX)

*Maybe ADR 0x1E = 0x31 is the correct setting for PRBS Generator.
  Though our customer set ADR 0x1E = 0x31, they could not get PRBS pattern.
------------------------------------------------------------------------------------------------

Q2)
is ADR0x1E[7:5] = 3'b100 correct for PRBS Generator setting ?

One thing we found is that Multiplexer setting on the datasheet seems to be wrong.
We need further evaluation but "0x4" may be the setting for Retimed Data.

Q3)
Please also tell us the default value for ADR 0x1B.

Best Regards,
Kawai

  • 0
    Guru 19785 points

    Our customer is in trouble. They need to complete their evaluation by the beginning of next week.

    Please help us on this item.

    Best Regards,
    Kawai

  • 0 in reply to Kawai
    TI__Intellectual 1705 points

    Hi,

    To enable the VCO free run PRBS generator, below are register settings.
    For DS100DF410 and DS110DF410, with the setting below, it will produce a frequency close to the 10.3125G.
     
    Please note the frequency setting is very course so it is not possible to get exact frequency 10.3125G. 
    Also the VCO frequency varies with process, voltage and temperature.
     
    0xFF       0x04       //Sel channel 0. If want to write to all channel registers, then change the value to 0x0C
    0x14       0x80       //SD Preset Enable
    0x09       0xEC      //Override charge pump power down, divider select, VCO cap count, LPF DAC, loopthru mux select
    0x1B      0x00       //Disable both charge pumps
    0x08       0x07       //Set VCO cap count to 07
    0x18       0x00       //Set divider to 1
    0x1F       0x52       //Set LPF DAC to 12
    0x1E       0x99       //Output Mux Select PRBS, enable PRBS Generator
    0x30       0x0A      //Powerup PRBS Clk, select PRBS31, set this register as 0x08 for PRBS9
    0x0D      0x20       //Enable PRBS Clock

    Regards,

    Michael

  • 0 in reply to Michael Hinh
    Guru 19785 points

    Michael-san,

    Thank you for your comment.

    We will ask customer to try setting with the above register value.

    Could you please give us your advice for the following questions, too.

     

    Q1)
    Is the setting of ADR 0x08 = 0x07 correct for datarate 10.3125Gbps ?
    Datasheet says to write ADR 0x08 = 0x0C for 10.3125Gbps.

    Q2)
    Is ADR 0x1E[7:5 ]= 3'b100 correct for PRBS Generator setting ?

    Q3)
    Is the default value for ADR 0x1B = 0x00 ?

    Q4)
    The value for ADR 0x1E is 0x99 in your answer.
    What is ADR 0x1E bit3 ?? Please give us the explanation.

    Best Regards,
    Kawai

  • 0 in reply to Kawai
    Guru 19785 points

    Michael-san,

    Our customer had tried with your register setting sequence, but they could not get the PRBS pattern output.

    Is there any other critical setting or condition to use PRBS generator ?

    As our customer can not move forward on their evaluation, they may not be able to meet their schedule.

    Please help us on this issue addition to the questions above.

    Best Regards,
    Kawai

  • 0 in reply to Kawai
    TI__Intellectual 1705 points

    Hi,

    The register values provided should enable the PRBS pattern from the free running VCO, there is no other settings or conditiion needed.

    Please ensure that customer is configurating the correct device. The device slave address is assigned by the ADDR_[3:0] pins.

    Also the first register to write is the control/shared register 0x0ff = 0x04 which selects CH0.
    If all channels is needed, then change the value to 0x0C.

    As for the questions, here are the answer.

    Q1)
    Is the setting of ADR 0x08 = 0x07 correct for datarate 10.3125Gbps ?
    Datasheet says to write ADR 0x08 = 0x0C for 10.3125Gbps.

    For the DS100DF410 and DS110DF410, the value for the CAP DAC count for register 0x08 = 07'h and LPF DAC register 0x1F = 12'h should set the VCO frequency close to the 10.3125G.
    For the DS125DF410, the value for the CAP DAC count for register 0x08 = 0B'h and LPF DAC register 0x1F = 0E'h should set the VCO frequency close to the 10.3125G.
    Please note that the frequency can vary from PVT so would need to adjust the CAP DAC and LPF DAC values.

    Q2)
    Is ADR 0x1E[7:5 ]= 3'b100 correct for PRBS Generator setting ?

    Bits[7:5] select the output mux to PRBS, need to also set bit4=1 to enable the PRBS.

    Q3)
    Is the default value for ADR 0x1B = 0x00 ?

    No, the default value for 0x1B is 0x03, which has bits[1:0]=11 and both PD and FD charge pump are enabled.


    Q4)
    The value for ADR 0x1E is 0x99 in your answer.
    What is ADR 0x1E bit3 ?? Please give us the explanation.

    The 0x1E bit3 is the DFE_PD, this bit is set to 1 by default and the DFE is powered down.
    So set this bit3 to 0 to enabled the DFE.

    Regards,

    Michael

  • 0 in reply to Michael Hinh
    Guru 19785 points

    Michael-san,

    We appreciate  for your support. Thank you very much.

    I was able to confirm with the evaluation board.

    One thing I found is that you cannot easily select PRBS Generator using the GUI. You need to program the registers manually.

    Q1) I understood that the datasheet is a typo.

    Q2) Thank you. I also confirmed using EVM.

    Q3) Thank you.

    Q4) I apologize for asking you this question. It was in the register map.

    As the customer still do not have PRBS output, I am asking their register settings.

    Thanks and Best Regards,

    Kawai

  • 0 in reply to Kawai
    Guru 19785 points

    Michael-san,

    ----------

    Please let me ask you about the CAPDAC setting for 10.3125Gbps.

    What happens if the customer sets to the value which is said in the datasheet?  (write ADR 0x08 = 0x0C for 10.3125Gbps)
    Can you still use with this value ?
    I am asked why the recommended setting is different from the datasheet.

    My guess is that the CAPDAC setting is shifted to lower data rate(ADR 0x08 = 0x07->0x0C), probably user may be able  to output 10.3125Gbps by  programming the LPFDAC value higher.

    ---------------

    I have another question.

    There seems to have typo in the datasheet middle of page32. There is following description. 

    "Notice that when this entire sequence has been completed, bits7:2 of register 0x09 will all be set."

    I have tested with my EVM but  I only found ADR 0x09 = 0xEC.

    Is this correct operation ?

    ----------

    Best Regards,
    Kawai

  • 0 in reply to Kawai
    TI__Expert 4150 points

    Hello Michael,

    With regards to the DS125DF410, you mention writing to channel register 0x1Fh with a value of 0x0Eh.    Channel register 0x1Fh is documented as "reserved' in the register map.   I understand that bits 4:0 control the LPF DAC setting, but you are suggesting that we clear bit #6.

    What is bit #6 in channel register 0x1Fh?    Would you please update the datasheet register map to reflect part functionality as described in the PRBS generator section?

    Don