1.2.2. GPIO Interface
Whenever the master issues a write condition (R/W=0), the data received on the I2C bus is used to update the general purpose output pins until a stop or a repeat start condition is encountered. Similarly, when the I2C master issues a read condition (R/W = 1), the values at the general purpose input pins are sampled at the ACK bit and transmitted serially over the I2C bus. This process continues until the master issues a stop or repeat start.