3.8.6 RF Calibration

The temperature-dependent drift of the XTAL-based RF can be corrected for the receive modes. There are 23 bytes reserved for this in the eepTrxCal.tempCal[0:22] EEPROM setting where frequency correction values can be stored in 8K increments. For more details, refer to sEEPromTrxCalib eepTrxCal. The required data must be provided by the XTAL supplier.

A frequency correction value is calculated together with the service-related eepServices.TMUL multiplier value based on the result of the latest temperature measurement. The firmware uses this value to correct the FFREQ1/2 settings that determine the output frequency of the fractional-N PLL.


Address	Name	Bit 7
0x001F	tempCal[0]	tempCal_0[7:0]
...	...	...
0x0035	tempCal[22]	tempCal_22[7:0]


Address Service0	Name	Bit 7	Bit 6	Bit 5	Bit 4	Bit 3	Bit 2	Bit 1	Bit 0
0x00FB	TMUL	TMUL[7:0]

An RF calibration process can be triggered at the following time points:

During the start-up of a Receive mode as the operating mode after the system start if enabled in eepTrxConf.sysStartConfig.RF_CAL


Address	Name	Bit 7	Bit 6	Bit 5	Bit 4	Bit 3	Bit 2	Bit 1	Bit 0
0x0019	sysStartConfig	RF_CAL	—	VCO_TUNE	IDLEModeSelector	—	TMDEN	OPM[1:0]

During the start-up of a Receive mode via the Set System Mode SPI command. See Set System Mode from Related Links.


Name	Bit 7	Bit 6	Bit 5	Bit 4	Bit 3	Bit 2	Bit 1	Bit 0
systemModeConfig	RF_CAL	—	VCO_TUNE	IDLEModeSelector	—	TMDEN	OPM[1:0]

In PollingMode for each service/channel configuration. See RF Calibration from Related Links.


Name	Bit 7	Bit 6	Bit 5	Bit 4	Bit 3	Bit 2	Bit 1	Bit 0
pollLoopConf[x].config	RfCalib	—	VCOtune	—	—	—	EOL	EOP

Note: No SPI command supports the RF calibration. It is only available in combination with the start of a Receive mode. The RF calibration itself does not initiate a temperature measurement. Microchip recommends carrying out the temperature measurement before executing the RF calibration.

The RF calibration requires additional time. See Timing Characteristics from Related Links.