RFM31 Datasheet, PDF (86/137 Pages) –

RFM31
Register 20h. Clock Recovery Oversampling Rate
Bit
D7
D6
D5
D4
D3
D2
D1
D0
Name
rxosr[7:0]
Type
R/W
Reset value = 01100100
Bit
7：0
Name
rxosr[7:0]
Function
Oversampling Rate.
3 LSBs are the fraction, default = 0110 0100 = 12.5 clock cycles per data bit
The oversampling rate can be calculated as rxosr = 500 kHz/(2^ndec_exp x RX_DR). The ndec_exp and the
dwn3_bypass values found at Address: 1Ch – IF Filter Bandwidth register together with the receive data rate (Rb)
are the parameters needed to calculate rxosr:
500×(1+2×dwn3_bypass)
rxosr = _{2ndec_exp-3 ×Rb×（1+enmanch）}
The Rb unit used in this equation is in kbps. The enmanch is the Manchester Coding parameter (see Reg. 70h,
enmach is 1 when Manchester coding is enabled, enmanch is 0 when disabled). The number found in the equation
should be rounded to an integer. The integer can be translated to a hexadecimal.
For optimal modem performance it is recommended to set the rxosr to at least 8. A higher rxosr can be obtained by
choosing a lower value for ndec_exp or enable dwn3_bypass. A correction in filset might be needed to correct the
channel select bandwidth to the desired value. Note that when ndec_exp or dwn3_bypass are changed the related
parameters (rxosr, ncoff and crgain) need to be updated.
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