14.1.1 Overview
This section describes the AT86RF212B to microcontroller interface. The interface comprises a slave SPI and additional control signals. This interface is connected to a SAM L21 master interface as shown below. The SPI timing and protocol are described in the sections below as well.
The SPI is used for register, Frame Buffer, SRAM, and AES access. The additional control signals are connected to the GPIO/IRQ interface of the microcontroller. The table below introduces the radio transceiver I/O signals and their functionality.
| Signal | Description |
|---|---|
| /SEL | SPI select signal, active low |
| MOSI | SPI data (master output slave input) signal |
| MISO | SPI data (master input slave output) signal |
| SCLK | SPI clock signal |
| CLKM |
Optional, Clock output, usable as: - microcontroller clock source and/or MAC timer reference - high precision timing reference |
| IRQ |
Interrupt request signal, further used as: - Frame Buffer Empty indicator |
| SLP_TR |
Multi purpose control signal (functionality is state dependent): - Sleep/Wakeup: enable/disable SLEEP state - TX start: BUSY_TX_(ARET) state - disable/enable CLKM |
| /RST | AT86RF212B reset signal; active low |
| DIG2 |
Optional, - IRQ_2 (RX_START) for RX Frame Time Stamping |