
19
8111C–MCU Wireless–09/09
AT86RF231
6.2
SPI Protocol
Each SPI sequence starts with transferring a command byte from the SPI master via MOSI (see
additional mode-dependent information.
Each SPI transfer returns bytes back to the SPI master on MISO. The content of the first byte
after reset. To transfer status information of the radio transceiver to the microcontroller, the con-
tent of the first byte can be configured with register bits SPI_CMD_MODE (register 0x04,
stated with XX on MOSI are ignored by the radio transceiver, but need to have a valid logic level.
Return values on MISO stated as XX shall be ignored by the microcontroller.
The different access modes are described within the following sections.
6.2.1
Register Access Mode
A register access mode is a two-byte read/write operation initiated by /SEL = L. The first trans-
ferred byte on MOSI is the command byte including an identifier bit (bit7 = 1), a read/write select
bit (bit 6), and a 6-bit register address.
On read access, the content of the selected register address is returned in the second byte on
Figure 6-4.
Packet Structure - Register Read Access
Note:
1. Each SPI access can be configured to return radio controller status information
On write access, the second byte transferred on MOSI contains the write data to the selected
Table 6-2.
SPI Command Byte definition
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Access Mode
Access Type
1
0
Register address [5:0]
Register access
Read access
1
Register address [5:0]
Write access
00
1
Reserved
Frame Buffer access
Read access
0
1
Reserved
Write access
00
0
Reserved
SRAM access
Read access
0
1
0
Reserved
Write access
1
ADDRESS[5:0]
0
XX
MOSI
PHY_STATUS(1)
READ DATA[7:0]
MISO
byte 1 (command byte)
byte 2 (data byte)