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LMH1218: REG 0x3E : Initialization using SigCon Architect

Kawai
Guru 19785 points
Part Number: LMH1218

Hi Team,

Please allow me to ask you about LMH1218 initialization register, REG 0x3E.

Q1). When does Channel Register REG 0x3E bit7 auto resets to the default value ?

Q2). Can we have correct evaluation result using SigCon Architect ? It seems to be changing REG 0x3E value to default.

Below is the initialization process.
Based on this procedure I wrote all the registers in "Low Level Page. (REG 0x3E = 0x00)
After I changed to "High Level Page" or "Eye Monitor Page", then went back to Low Level Page, REG 0x3E register value was changed to default "0x80".

Is this a bug in SigCon Architect ?
The value of REG 0x3E stayed at "0x00" even after CDR Reset step, so, I believe when changed to "High Level Page" or "Eye Monitor Page", SigCon Architect runs a script and changes the register value in back ground.

Best Regards,

Kawai

  • 0
    TI__Mastermind 29655 points
    Hi Kawai-san,

    1. SigCon Architect automatically write Reg 0x3E = 0x00 (as shown in the initialization) in two instances: (1) When opening the LMH1218 GUI High Level Page for the first time; (2) when clicking "Reset Device." If the user every power cycles the LMH1218 and does not close/re-open SigCon Architect or click "Reset Device" after the power cycle, then it is possible that Reg 0x3E returns to its default value of 0x80.

    2. I will need to check this behavior in our lab. Please allow me a day to get back to you regarding this issue.

    Thanks,

    Michael
  • 0 in reply to Michael Lu (Santa Clara)
    TI__Mastermind 29655 points
    Hi Kawai-san,

    After investigating the LMH1218 SigCon Architect GUI, I have found what is going on.

    Both High Level and Eye Monitor Page has a read-back field for both HEO and VEO measurements. When looking at the macros executed for these functions, I see that the readback calls for Reg 0x3E=0x80 in order to obtain these measurements. The register is never set back to 0x00 by the software. This is why you are seeing Reg 0x3E = 0x80 after you go to the High Level Page and return to the Low Level Page.

    While this is not necessarily an issue that will cause a significant difference in device performance, I understand that you wish to maintain the initialization script settings whenever you are on the High Level or Eye Monitor Page.

    To resolve this issue, I recommend the following:

    1. I noticed that upon opening SIgCon Architect for the first time or clicking "Reset Device," only Channel Reg 0x16 = 0x25 is being set according to Table 10. The remainder of the Table 10 register programming is not being automatically written by the software. Therefore, please write the remaining registers from Table 10 in the Low Level Page:
    Reg 0x3E = 0x00
    Reg 0x55 = 0x02
    Reg 0x6A = 0x00

    2. To prevent Reg 0x3E = 0x80 on the High Level Page and Eye Monitor Page, the macro that reads back the HEO and VEO value must be modified. I will send you an e-mail separately with instructions regarding how to do this.

    Thanks,

    Michael
  • 0 in reply to Michael Lu (Santa Clara)
    Guru 19785 points
    Hi Michael-san,

    Thanks for the investigation. Please allow me to ask you a little more.

    Q3). By having the REG 0x3E = 0x00, what may occur to the device operation ? If possible, could you please tell us what this bit 7 is ?
    Customer is seeing error in their test. Register review is ongoing however I found this bit was not set correctly.

    Q4). For me, it seemed that REG 0x3E is written back to "0x80" always when selecting "High Level Page" or "Eye Monitor Page", not only for the first time. Could you double check in this point ?

    Q5). Please also allow me to double check whether there is a function that initialization script runs automatically when using SigCon Architect. If it does, at which timing does this initialization script run ?

    I was trying to investigate the script running in background, however, SigCon Architect script recording function only shows the script file name that I could not go deeper since no such files found underneath the SigCon Architect folder.

    Best Regards,
    Kawai
  • 0 in reply to Kawai
    TI__Mastermind 29655 points
    Hi Kawai-san,

    3. This bit is the HEO/VEO Lock Monitor Enable bit. This bit allows the LMH1218 to automatically obtain the HEO/VEO values periodically (approximately every 65 ms), and this is what is used by the GUI in order to read-back the most recent HEO/VEO values in the High Level and Low Level Page. There is a way to adjust the macros used by the GUI such that Reg 0x3E = 0x80 does not need to be written. I have sent you a separate e-mail regarding this topic.

    4. Please see response (3). I have also sent you a separate e-mail regarding why this mechanism occurs for those pages.

    5. I have seen that from testing the GUI today that only the "Enable Full Temperature Range" initialization appears to be running during initialization. You will need to manually write the remaining steps in Table 10. This script executes either (1) when opening the High Level Page for the first time after opening SigCon Architect or (2) after clicking "Reset Device."

    Please refer to my separate e-mail and we can discuss further if needed.

    Thanks,

    Michael
  • 0 in reply to Michael Lu (Santa Clara)
    Guru 19785 points
    Hi Michael-san,

    Sorry for my delay. Thanks for your support.

    Best Regards,
    Kawai