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 pull-up resistor. With few exceptions, it is the responsibility of the I3C Master to provide open-drain class pull-up resistor when the bus is in the open drain mode.

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