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BQ34Z950 SMBus access through DQ

Evan Sawyer
Expert 3175 points

Other Parts Discussed in Thread: BQ34Z950

Hello team!

I have a customer who has a couple of questions regarding the BQ34Z950:

The basic problem we are trying to address is that we have a need to write some SMBus accessible register and have the results of that write be readable on the DQ interface.

 

We attempted to do this with the SHA-1 registers; however, at least via the EVSW, it would not accept a partial SMBus block write (<20 bytes) and would only accept a full block which forced the SHA-1 response to be generated.  This invalidated using that buffer as a scratch pad register.

 

We have identified that we can do this with the Serial Number field (by unlocking DF).

 

There does appear to be a DQ register (0x0C) labeled VTS/ID which looks like it was something for EDV algorithms but it’s labeled in this part as read only.

 

Is there a DF block/offset which stores the value for the DQ VTS/ID register?  It would be more convenient for us if this was possible.

Thanks for the help!!

  • 0
    TI__Expert 3175 points

    Hi Mike,

    Thank you for your earlier reply. My customer is still working with this part and trying to understand the SMBus and DQ interfaces. Specifically they would like to know if there are any SMBus writable places which can also be read via DQ. Here is the question as posed by the customer:

  • 0 in reply to Evan Sawyer
    TI__Intellectual 2650 points

    Hi Evan,

    As I understand , no .

    As I indicated before in my email the only available DQ commands are those in this table.

    I am not familar with VTS/ID as I previously indicated. What is that. I find nothing in a search of TRM.

    To access other locations you would need a command to acess that location and there is no suitable generic read address# command  available that I see .

    I have forwarded question to the firmware team but don't hold much hope.

    Mike

     

  • 0 in reply to Mike Ewer
    Guru 25210 points

    Mike,

    Your last reply to this post is not accurate.

    The pasted graphic you posted is from Appendix C of SLUUA93 which is the BQ34Z950 Technical Reference Manual. The information in Appendix C is incomplete and misleading. That table shows the "Extended DQ Commands" that the BQ34Z950 supports, but missing are the normal DQ commands that the device supports.

    There is a document called the "bq34z950 Technical Reference Addendum" that is dated June 26th 2014 and watermarked "DRAFT". This document lists the information that was missing from SLUUA93.

    One of the normal DQ commands documented is "VTS/ID", location 0x0C, read-only, that returns an 8-bit value. (See paste below). The document defines this field as "This location is available for manufacturing codes or other information. It has no effect on the operation of the device."

    I believe the OP of this thread is asking if there is a corresponding data flash (DF) location where this value is stored, that they could then program via SMBus interface.

  • 0 in reply to Brian Boorman
    TI__Guru 73830 points
    The bq34z950 firmware uses the VTS/ID as read only and it is initialized in the source code at boot / reset time. It is not loaded from the data flash or otherwise configurable.