When the Slave is powered off, its input protection diodes will clamp the SCL & SDA lines to within 0.5V of its supply lines.
If unpowered, that's 0.5V. Both SCL & SDA low will keep I2C from operating.
When the Slave is powered off, its input protection diodes will clamp the SCL & SDA lines to within 0.5V of its supply lines.
If unpowered, that's 0.5V. Both SCL & SDA low will keep I2C from operating.