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RFM 67W

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Table 7

Example Standard Bitrates and their Corresponding Register Settings.

Type

BrMSB

BrLSB

(G)FSK, (G)MSK

OOK

Rb Actual (to 7s.f.)

0x68

0x2B

1.2 kbps

1.2 kbps

1200.015

0x34

0x15

2.4 kbps

2.4 kbps

2400.060

0x1A

0x0B

4.8 kbps

4.8 kbps

4799.760

0x0D

0x05

9.6 kbps

9.6 kbps

9600.960

0x06

0x83

19.2 kbps

19.2 kbps

19196.16

0x03

0x41

38.4 kbps

38415.36

0x01

0xA1

76.8 kbps

76738.60

Classical modem baud rates

(multiples of 1.2 kbps)

0x00

0xD0

153.6 kbps

153846.1

0x02

0x2C

57.6 kbps

57553.95

Classical modem baud rates

(multiples of 0.9 kbps)

0x01

0x16

115.2 kbps

115107.9

0x0A

0x00

12.5 kbps

12.5 kbps

12500.00

0x05

0x00

25 kbps

25 kbps

25000.00

0x80

0x00

50 kbps

50000.00

0x01

0x40

100 kbps

100000.0

0x00

0xD5

150 kbps

150234.7

0x00

0xA0

200 kbps

200000.0

0x00

0x80

250 kbps

250000.0

Round bit rates

(multiples of 12.5, 25 and

50 kbps)

0x00

0x6B

300 kbps

299065.4

Watch Xtal frequency

0x03

0xD1

32.768 kbps

32.768 kbps

32753.32

5.2. Synthesizer

The frequency synthesizer of the RFM67W is a fully integrated fractional-N third-order sigma-delta phase-locked loop

and VCO. Also incorporated are fully integrated third-order and low pass filters which determine the loop bandwidth. All of

these features are fully automated and derived from the user bitrate and frequency deviation settings, as described in

Sections

5.1.1 to 5.1.3.

To ensure the frequency accuracy of the PLL output it is necessary to perform calibration. The calibration process is

performed automatically upon power up of the RFM67W. However, the calibration feature is also accessible to the user

via the SPI configuration register, PllStat (address 0x0A). The calibration is performed by setting bit 2 (pll_cal) high. This

ensures that the frequency output accuracy is limited only by the frequency error of the crystal oscillator, the calibration

procedure lasts 500 µs, during which time pll_cal_done (bit 4 of address 0x0A) is set low. Once complete pll_cal_done is

set high and confirmation of a successful calibration can be obtained by reading pll_cal_ok.