For input value 1, the I2C-IR IOState register bit0 is set to value 1, and sleep-mode is enabling by setting IER register bit4(same register pokes done when a data transfer ends). For input value 0, those register bits are set to value 0 instead of 1(same register pokes done when a data transfer starts). These register pokes are only done automatically for data-transfer start/end when the value for IRU:SetSleepModeActive is value 1.