Status register, SSPSR on page 3-7
| TFE | Transmit FIFO empty, RO: 0 Transmit FIFO is not empty. 1 Transmit FIFO is empty. |
| TNF | Transmit FIFO not full, RO: 0 Transmit FIFO is full. 1 Transmit FIFO is not full. |
| RNE | Receive FIFO not empty, RO: 0 Receive FIFO is empty. 1 Receive FIFO is not empty. |
| RFF | Receive FIFO full, RO: 0 Receive FIFO is not full. 1 Receive FIFO is full. |
| BSY | PrimeCell SSP busy flag, RO: 0 SSP is idle. 1 SSP is currently transmitting and/or receiving a frame or the transmit FIFO is not empty. |