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DRV8873: nFault-Pin, Status-Register Fault-Bit in Daisy-Chain-Configuration

Sebastian Reinig1
Prodigy 40 points
Part Number: DRV8873


Hi,

 

For a Daisy Chain Configuration the datasheet on the one hand says: „Status-Bytes must start with 1 and 1 for the two MSBs.“ On the other hand at the registers description it says that the Bit-6 is a FAULT-Bit which „compliments the nFault-Pin.“

Is it correct that under normal operating conditions when there is no Fault detected the nFault-Pin is high while the Fault-Bit is low? As consequence the 2 MSBs of the Status-Bytes are 10 instead of always 11. How is it then possible to detect a Status-Byte when Bit-6 depends on if there is a Fault condition or not? 

 

Best Regards,

Sebastian Reinig

  • 0
    TI__Expert 8985 points

    Hi Sebastian,

    Answers inline:

    Is it correct that under normal operating conditions when there is no Fault detected the nFault-Pin is high while the Fault-Bit is low? 

    -> Yes, that is correct.

    As consequence the 2 MSBs of the Status-Bytes are 10 instead of always 11.

    -> The two MSbs will be constant and set to 11. Please, read the end of Page 33 and interpret the Figure 28. Those first two MSBs are constant and are an indicator that you are reading a status byte.

    How is it then possible to detect a Status-Byte when Bit-6 depends on if there is a Fault condition or not? 

    -> Since MSbs are 11, what you need to read are the following 6 bits in that status register Sx. Those 6 bits are indicators of the type of fault generated. Figure 28 illustrates this answer.