The next phase of the control transfer is the data phase. Depending on the request that was communicated in the setup phase the host will either request data from the device or send data to the device. In this slide the flow diagram is shown for the host expecting the device to return the requested data. As a result of the setup phase, since the request from the host was a GET request the firmware had already loaded the data into the IN endpoint FIFO and set the INPRDY flag to notify the SIE that there is valid data waiting on the host IN request. Once the IN request is received the SIE again determines the validity of the packet and checks the INPRDY bit to make sure the data is ready. If it is not set the SIE automatically generates NAK response to the host. If the bit is set then the SIE sends the data from the FIFO and sets the interrupt flag. Once the interrupt is pended the firmware will load more data to the FIFO and set the INPRDY bit once again. If this is the last packet the firmware will also set the DATAEND bit. This allows the SIE to generate the acknowledge sequence required by the control transfer status phase.