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TPS65982: Start timing of I2C communication

Takashi Onawa
Genius 13200 points
Part Number: TPS65982
Other Parts Discussed in Thread: TPS65981

Hi Team,

In my customer's prototype board, It seems that EC sometimes fails reading some registers at start up timing.

When is I2C bus communication available at TPS65982 start up timing?
And are there any ways to know that I2C bus and internal registers are ready for read? 

Regards,

Takashi Onawa

  • 0
    TI__Mastermind 36756 points
    Hi Onawa-san,

    The internal registers can always be read when the device is powered, even before the device has loaded a configuration image. However most of these values will change when the device is reading from the flash and configuring the internal registers.
    I expect the customer is seeing issues when they are trying to read registers while the TPS65982 is reading from the SPI-flash chip. I would recommend polling the MODE register and waiting until it reads back APP before attempting to to any other reads.

    Thank you,
    Eric
  • 0 in reply to Eric Beljaars
    TI__Genius 13200 points
    Hi Eric-san,

    Thanks, I understood they to read MODE register before reading registers at device start up timing.

    Regards,
    Takashi Onawa
  • 0 in reply to Takashi Onawa
    TI__Genius 13200 points
    Hi Eric-san,

    Sorry, I got one another question from the customer, regarding I2C access at start up timing

    Are the following registers changed before and after the MODE register becomes APP?
    The customer want to read the register prior to the polling to minimize waiting time.

    Please let me know if there are the register which might be changed.

    0x06 CUSTUSE
    0x08 Cmd1
    0x09 Data1
    0x14 IntEventX, IntMaskX, IntClearX
    0x15 IntEventX, IntMaskX, IntClearX
    0x16 IntEventX, IntMaskX, IntClearX
    0x17 IntEventX, IntMaskX, IntClearX
    0x18 IntEventX, IntMaskX, IntClearX
    0x19 IntEventX, IntMaskX, IntClearX
    0x1A Status Register
    0x32 TX Source Capabilities Register..
    0x34 Active Contract PDO
    0x50 Data Control
    0x51 DP SID Configuration
    0x5F Data Status
    0x72 GPIO Status

    Regards,
    Takashi Onawa
  • 0 in reply to Takashi Onawa
    TI__Genius 13200 points
    Hi Eric-san,

    Also, If you have a diagram for MODE transition, Could you share it with us?
    I didn't make sure from our manuals whether the mode accidentally transitions from APP to another or not.

    Regards,
    Takashi Onawa
  • 0 in reply to Takashi Onawa
    TI__Genius 16370 points
    Takashi San,

    Except for a small subset, the device doesn't allow access to the internal registers and 4CC command while booting - The registers you listed in your above post (except for CMDx and DATAx) are not part of that subset. The host is allowed access to the full register set after the MODE transitions to 'APP'. Chapter-3 of 'www.ti.com/.../slvuah7b.pdf' details the boot flow, but we don't have a document explaining the transitions of MODE register. I'd nevertheless be happy to help if you have any specific questions on the topic.

    -/Praneet
  • 0 in reply to Praneet Kumar
    TI__Genius 13200 points
    Hi Praneet-san,

    Thanks for telling the detail.

    > The host is allowed access to the full register set after the MODE transitions to 'APP'. Chapter-3 of 'www.ti.com/.../slvuah7b.pdf'

    The link seems to be expired. Could you tell me the document name?

    Also, My customer would like to know roughly how much time it will take from power up to showing APP on MODE register. Is it possible to estimate the duration roughly?

    Regards,
    Takashi Onawa
  • 0 in reply to Takashi Onawa
    TI__Genius 13200 points
    Hi Praneet-san or Anyone in the team,

    Can I have any comment for the question above?


    Regards,
    Takashi Onawa
  • 0 in reply to Takashi Onawa
    TI__Genius 16370 points
    Takashi San, Please refer the document titled 'TPS65981, TPS65982, and TPS65986 Firmware User’s Guide (Rev. B)' @ 'www.ti.com/.../technicaldocuments'. I never profiled it but can get you the numbers, but this boot time cannot obviously be eliminated - The device has to load the firmware from sFLASH to start working.

    -/Praneet
  • 0 in reply to Praneet Kumar
    TI__Genius 13200 points

    Hi Kumar-san,

    Thanks.

    We are understanding that the load time can't not eliminate at start up time.

    They'd like to define "Timeout" to distinguish Flash read mistake or Flash failure by the sequence below. they think that the information is needed to determine the "Timeout" duration.

    Regards,

    Takashi Onawa

  • 0 in reply to Takashi Onawa
    TI__Genius 13200 points
    Hi Kumar-san,

    Can I get any comments to close this issue? My customer is demanding us to clarify the time roughly to define the "Timeout" duration in their app's FW.

    > Also, My customer would like to know roughly how much time it will take from power up to showing APP
    >on MODE register. Is it possible to estimate the duration roughly?

    Regards,
    Takashi Onawa
  • 0 in reply to Takashi Onawa
    TI__Genius 16370 points
    Wait for 500ms after POR or GAID, and read register 0x2D - If 'BootOK' is set, the boot is successful and MODE register will read APP.

    -/Praneet
  • 0 in reply to Praneet Kumar
    TI__Genius 13200 points
    Hi Kumar-san,

    Thank you for the clear answer. I understood.

    Regards,
    Takashi Onawa