2.9.7 RF Calibration

The temperature-dependent drift of the XTAL-based RF frequency can be corrected for the data transmit and 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 (see sEEPromTrxCalib eepTrxCal for details). 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. This value is used by the firmware to correct the FFREQ1/2 settings that determine the output frequency of the fractional-N PLL.

Address

Name

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

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 or transmit 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 ANT_TUNE VCO_TUNE IDLEModeSelector — TMDEN OPM[1:0]
  • During the start-up of a receive or transmit mode via the “Set System Mode” SPI command (see Set System Mode).
Name Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0
systemModeConfig RF_CAL ANT_TUNE VCO_TUNE IDLEModeSelector — TMDEN OPM[1:0]
  • In PollingMode for each service/channel configuration. For more details, see RF Calibration.

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 data transmit or receive mode. The RF calibration itself does not initiate a temperature measurement. Microchip recommends carrying out the temperature measurement before the RF calibration is executed.

The RF calibration requires additional time, see Timing Characteristics.