14.2.1.2.7 BUSY_TX - Transmit State

In the BUSY_TX state AT86RF212B is in the data transmission state.

A transmission can only be initiated from the PLL_ON state. The transmission can be started either by driving event such as:

A rising edge on pin 11 (SLP_TR), or
A serial TX_START command via the SPI to the TRX_CMD bits in the TRX_STATE register (TRX_STATE.TRX_CMD).

Either of these forces the radio transceiver into the BUSY_TX state.

During the transition to the BUSY_TX state, the PLL frequency shifts to the transmit frequency. The actual transmission of the first data chip of the SHR starts after one symbol period (see note) in order to allow PLL settling and PA ramp-up. After transmission of the SHR, the Frame Buffer content is transmitted. In case the PHR indicates a frame length of zero, the transmission is aborted immediately after the PHR field.

After the frame transmission has been completed, the AT86RF212B automatically turns off the power amplifier, generates an IRQ_3 (TRX_END) interrupt, and returns into PLL_ON state.

Note: Throughout this datasheet, a “symbol period” refers to the definition described in the Symbol Period section.