SPDR – SPI Data Register is a read/write register
When using the I/O specific commands IN and OUT, the I/O addresses 0x00 - 0x3F must be used. When addressing I/O Registers as data space using LD and ST instructions, 0x20 must be added to these offset addresses.
| Bit7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
| SPIDn[7:0] | |||||||
| AccessR/W | R/W | R/W | R/W | R/W | R/W | R/W | R/W |
| Resetx | x | x | x | x | x | x | x |
SPI Data
The SPI Data Register is a read/write register used for data transfer between the Register File and the SPI Shift Register. Writing to the register initiates data transmission. Reading the register causes the Shift Register Receive buffer to be read.