RFM22
Register 74h. Frequency Offset 2
Bit
D7
D6
D5
D4
D3
D2
D1
D0
Reserved
R
fo[9:8]
R/W
Name
Type
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
(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.
1:0
fo[9:8]
Register 75h. Frequency Band Select
Bit
D7
Reserved
R
D6
sbsel
R/W
D5
D4
D3
D2
fb[4:0]
R/W
D1
D0
hbsel
R/W
Name
Type
Reset value = 01110101
Bit
7
Name
Reserved Reserved.
Function
sbse
6
Side Band Select.
High Band Select.
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.
5
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
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.
fb[4:0]
4:0
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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