RFM22 Datasheet, PDF (137/150 Pages) –

RFM22
Register 74h. Frequency Offset 2
Bit
D7
D6
D5
D4
D3
D2
D1
D0
Name
Reserved
fo[9:8]
Type
R
R/W
Reset value = 00000000
Bit
Name
Function
7:2 Reserved Reserved.
Upper Bits of the Frequency Offset Setting.
fo[9] is the sign bit. The frequency offset can be calculated as Offset = 156.25 Hz x
1:0
fo[9:8]
(hbsel + 1) x fo[7:0]. fo[9:0] is a twos complement value. Reading from this register
will give the AFC correction last results, not this register value.
Register 75h. Frequency Band Select
Bit
D7
D6
D5
D4
D3
D2
D1
D0
Name Reserved
sbsel
hbsel
fb[4:0]
Type
R
R/W
R/W
R/W
Reset value = 01110101
Bit
Name
Function
7
Reserved Reserved.
6
sbse Side Band Select.
High Band Select.
5
hbsel Setting hbsel = 1 will choose the frequency range from 480–930 MHz (high bands). Setting
hbsel = 0 will choose the frequency range from 240–479.9 MHz (low bands).
Frequency Band Select.
Every increment corresponds to a 10 MHz Band for the Low Bands and a 20 MHz
Band for the High Bands. Setting fb[4:0] = 00000 corresponds to the 240–250 MHz
4:0
fb[4:0]
Band for hbsel = 0 and the 480–500 MHz Band for hbsel = 1. Setting fb[4:0] = 00001
corresponds to the 250–260 MHz Band for hbsel = 0 and the 500–520 MHz Band for
hbsel = 1.
The RF carrier frequency can be calculated as follows:
fcarrier = (fb+24+(fc+fo) / 64000) x 10000 x (hbsel+1) + (fhch x fhs x 10) [kHz],
where parameters fc, fo, fb and hb_sel come from registers 73h–77h. Parameters fhch and fhs come from register
79h and 7Ah.
137
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