RFM22 Datasheet, PDF (48/150 Pages) –

RFM22
Table 19. ndec[2:0] Settings
Rb(1+ enmanch) [kbps]
Min
Max
0
1
1
2
2
3
3
8
8
40
40
65
ndec[2:0]
5
4
3
2
1
0
The clock recovery oversampling rate is set via rxosr[10:0] in "Register 20h. Clock Recovery Oversampling Rate"
and "Register 21h. Clock Recovery Offset 2".
ndec_exp and dwn3_bypass together with the receive data rate (Rb) are used to calculate rxosr:
500×(1+2×dwn3_bypass)
rxosr = _{2ndec_exp-3 ×Rb×（1+enmanch）}
Where: Rb is in kbps and enmanch is the Manchester Coding parameter. The resulting rxdr[10:0] value should be
rounded to an integer hexadecimal number.
The clock recovery offset ncoff[19:0] in "Register 21h. Clock Recovery Offset 2", "Register 22h. Clock Recovery
Offset 1", and "Register 23h. Clock Recovery Offset 0" is calculated as follows:
Rb×（1+enmanch）×2^20+ndec_exp
ncoff = _{500×(1+2×dwn3_bypass)}
Where: Rb is in kbps.
The clock recovery gain crgain[10:0] in "Register 24h. Clock Recovery Timing Loop Gain 1" and "Register 25h.
Clock Recovery Timing Loop Gain 0" is calculated as follows:
2¹⁶
crgain = 2 + _rxosr
48
Tel: [phone] Fax: [phone] E-mail: [e-mail] http://www.hoperf.com