Transmit state output power is configured through pin control or the SPI interface.
When configuring output power through pins, use MODE to set one of two preset values to the TX power control. Preset values update the TX_Gain value when MODE control changes in the Program state. The same functionality is enabled by writing to the MODE bit in CONFREG0. Custom preset values are stored in UICR and selected as default.
The SPI interface can control the output power. From Program state, and before entering the Transmit state, TX_Gain is configured by writing the gain value over SPI to the TX_GAIN field in the CONFREG0 register. SPI write overwrites the initialization TX_Gain value. The Transmit state can then be entered by writing CONFREG0.TX_EN in the same SPI write cycle, or later by using TX_EN pin.
Changing MODE or the MODE bit in CONFREG0 triggers a reload of a default value to TX_Gain. Setting MODE or the MODE bit loads POUTB. Clearing MODE or the MODE bit loads POUTA. The default value is used when a new value is loaded to TX_Gain during the SPI write cycle. This changes the MODE bit. When a new value is loaded to TX_Gain during the SPI write cycle, the default value is used, changing the MODE bit.
The following table shows TX power control with MODE control and corresponding preset values of TX_Gain in Program state.
| MODE | POUTA_SEL | POUTB_SEL | TX_Gain | Description |
|---|---|---|---|---|
| 0 | 0 | X | POUTA_PROD | Chip production default value used |
| 1 | X | 0 | POUTB_PROD | Chip production default value used |
| 0 | 1 | X | POUTA_UICR | End-user default value used |
| 1 | X | 1 | POUTB_UICR | End-user default value used |