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BQ20z75-V180 - Multi-master configuration

Ganesh THIRUGNANAM
Prodigy 30 points
Other Parts Discussed in Thread: BQ20Z75-V180, BQ24725, AM3517

Hi All,

I am using BQ20Z75-V180 Gas Gauge in my Battery pack. I have enable SBS commands for charing my Battery through Battery Charger IC BQ24725.

Periodically every 30 seconds BQ20Z75-V180 sends Voltage and Current information to Charger IC BQ 24721.

Both ICs are connected overy I2C/SMBUS lines. And also I have my Computer Module I2C connected to the same bus for reading Battery status from Battery pack.

My computer module (AM3517) I2C support Multi-master and it handles Bus arbitration.

I would like to know whethe BQ20Z75 support Multi-master and it handles Bus arbirtration or not. Can somebody help me confirming the multi-master support and bus arbitration handle in BQ20Z75-V180

Reason asking above confirmation is that if both computer module and BQ20Z75 start communicating at same time then any one should take the control and other one should wait for stop command to start its communication.

Regards

Ganesh

 

  • 0
    TI__Guru 73830 points

    Ganesh

    The bq24725 only works as a slave. The bq20z75 does support arbitration.

    This comment is from one of our applications reports,"An SMBus Master can only start a packet if the SMBus has been idle for more than 50 microseconds. Once this requirement has been met, then the Master immediately “grabs” the bus by sending a start bit. All TI FG’s function exactly like this and since they are hardware controlled SMBus Engines, they easily detect idle. This type of behavior is very difficult to create for an SMBus engine implamented in firmware. It is easy to detect 50 microseconds of idle time, but then the port pins used to create the bus must be switched to outputs and then the start bit must be sent. During this time, there is a window where another Master may actually grab the bus. The firmware controlled bus then does not know that the bus is no longer busy. We then lose arbitration."

    Regards
    Tom

  • 0 in reply to ThomasCosby
    Prodigy 30 points

    Hi Tom,

    Thanks for the response and I understood the implementation in BQ20Z75 as master.

    Regards

    Ganesh