SPI Interrupt Status
| RXRDY | Receiver Ready flag. |
| TXRDY | Transmitter Ready flag. |
| RXOV | Receiver Overrun interrupt flag. |
| TXUR | Transmitter Underrun interrupt flag. |
| SSA | Slave Select Assert. |
| SSD | Slave Select Deassert. |
| RESERVED | Reserved. Read value is undefined, only zero should be written. |
| MSTIDLE | Master Idle status flag. |
| RESERVED | Reserved. Read value is undefined, only zero should be written. |