RFM42B Datasheet, PDF (22/51 Pages) List of Unclassifed Manufacturers – ISM TRANSMITTER

RFM42B/43B
3.5.5. Frequency Offset Adjustment
A frequency offset can be adjusted manually by fo[9:0] in registers 73h and 74h. The frequency offset adjustment is
implemented by shifting the Synthesizer Local Oscillator frequency. This register is a signed register so in order to
get a negative offset it is necessary to take the twos complement of the positive offset number. The offset can be
calculated by the following:
DesiredOffset  156.25Hz  (hbsel 1)  fo[9 : 0]
fo[9 : 0]  ^{DesiredOffset}
156.25Hz  (hbsel 1)
The adjustment range in high band is ±160 kHz and in low band it is ±80 kHz. For example to compute an offset of
+50 kHz in high band mode fo[9:0] should be set to 0A0h. For an offset of –50 kHz in high band mode the fo[9:0]
register should be set to 360h.
Add R/W Function/Descript D7
D6
D5
D4
D3
D2
D1 D0 POR
ion
Def.
73 R/W Frequency Offset
fo[7]
fo[6]
fo[5]
fo[4]
fo[3]
fo[2] fo[1] fo[0] 00h
74 R/W Frequency Offset
fo[9] fo[8] 00h
3.5.6. TX Data Rate Generator
The data rate is configurable between 0.123–256 kbps. For data rates below 30 kbps the ”txdtrtscale” bit in register
70h should be set to 1. When higher data rates are used this bit should be set to 0.
The TX date rate is determined by the following formula in kbps:
DR_TX (kbps) = -^t--^x2---^d-₁--₆-^r--^-₊-¹---₅-⁵---_^:--⁰-_t--_x-^--_d-^--_t-_r--¹_t--_s---_c^M--_a---^H_l--_e--^z--
txdr[15:0] = -^D----^R----^_----^T---^X----⁽--^k---^b----^p---^s---⁾-₁--^---_M--²---_H-¹--⁶--_z--⁺----⁵----^---^t--^x---^d---^t-^r--^t--^s---^c--^a---^l--^e-
Add R/W Function/Description D7
D6
D5
D4
D3
D2
D1 D0 POR Def.
6E R/W
TX Data Rate 1
txdr[15] txdr[14] txdr[13] txdr[12] txdr[11] txdr[10] txdr[9] txdr[8] 0Ah
6F R/W
TX Data Rate 0
txdr[7] txdr[6] txdr[5] txdr[4] txdr[3] txdr[2] txdr[1] txdr[0] AAh
Tel: [phone] Fax: [phone] E-mail: [e-mail] http://www.hoperf.com
22