Much of the activity on the I3C Bus is in push-pull mode (that is, with the pull-up resistor disabled) in order to achieve higher data rate. However for some Bus management activities, and for backwards compatibility with I2C, pull-up-resistor-based open-drain mode is enabled. For example: arbitration during Dynamic Address Assignment, and In-Band Interrupt. Also, the ACK/NACK during the 9th bit is done using a pull-up resistor. With few exceptions, it is the responsibility of the I3C Master to provide an open-drain class pull-up resistor when the Bus is in the open drain mode.

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