SPI FIFO global update register
| SPI0RXUPDATESIZE | Writing 1 updates SPI0 Rx FIFO size to match the SPI0 RXSIZE. Must be done for all SPIs when any SPI RXSIZE is changed. |
| SPI1RXUPDATESIZE | Writing 1 updates SPI1 Rx FIFO size to match the SPI1 RXSIZE. Must be done for all SPIs when any SPI RXSIZE is changed. |
| RESERVED | Reserved. Read value is undefined, only zero should be written. |
| SPI0TXUPDATESIZE | Writing 1 updates SPI0 Tx FIFO size to match the SPI0 TXSIZE. Must be done for all SPIs when any SPI TXSIZE is changed. |
| SPI1TXUPDATESIZE | Writing 1 updates SPI1 Tx FIFO size to match the SPI1 TXSIZE. Must be done for all SPIs when any SPI TXSIZE is changed. |
| RESERVED | Reserved. Read value is undefined, only zero should be written. |