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BQ20Z80A-V110 extended SBS command timing

Scott Phillips
Intellectual 310 points

For the extended SBS commands you must first write the two byte command to ManufacturerAccess(0x00) and then read from ManufacturerAccess(0x00) to get the result.

What is the minimum time delay necessary between a write and read from ManufacturerAccess?

If I follow the two byte write to ManufacturerAccess immediately with a read, I sometimes read back the data from the previous command.  If I put a delay between the read and write, I always seem to get the expected data back.

For example:

Write 0x0051 to ManufacturerAccess

Read ManufacturerAccess - I get the result from the SafetyStatus register back

Write 0x0053 to ManfacturerAccess

Read ManufacturerAccess - Sometimes I get the result from the PFStatus register, but other times I get the result from the SafetyStatus register

If, however, I add a delay between the write to and read from ManufacturerAccess, I get the correct response back.

I could not find any SMBus timing specifications in the datasheet related to switching from a write to a read command.

Thanks for your help -

Scott

  • 0
    TI__Intellectual 2120 points

    Hi Scott,

       Are you waiting beyond the tBUF time of 4.7us (min)? Out of curiosity, when you insert your delay, how long are you waiting?

    Best regards

    Garry

  • 0 in reply to Garry Elder
    Intellectual 310 points

    I don't have a very fine resolution on my delays.  Currently I put in a 2msec delay and that seems to work.  I, however, do not know what the actual minimum time is. 

    I am running into a similar problem with sending the seal command and the permanent failure clear command.  How long do I have to wait after sending the 2 word commands before I can check the status bits in OperationStatus and PFstatus?

    It would seem that when you send a write command to ManufacturerAccess, it takes a period of time for the chip to execute the command.  This time period, however, does not seem to be documented.

    Thanks for your help -

    Scott

  • 0 in reply to Scott Phillips
    TI__Intellectual 2120 points

    Hi Scott,

      1ms is enough for most except if there its the Authenticate command which requires 100ms.

    Best regards

    Garry