SPI Data Register. This bi-directional register provides the transmit and receive data for the SPI. Transmit data is provided to the SPI0 by writing to this register. Data received by the SPI0 can be read from this register.
| DATALOW | SPI Bi-directional data port. |
| DATAHIGH | If bit 2 of the SPCR is 1 and bits 11:8 are other than 1000, some or all of these bits contain the additional transmit and receive bits. When less than 16 bits are selected, the more significant among these bits read as zeroes. |
| RESERVED | Reserved, user software should not write ones to reserved bits. The value read from a reserved bit is not defined. |