Rf12b – Rainbow Electronics RF12B User Manual

Page 15

RF12B

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3. Frequency Setting Command

bit 15 14 13 12 11 10 9 8

7 6 5 4

3 2 1 0 POR

f11 f10

f1 f0 A680h

The 12-bit parameter F (bits f11 to f0) should be in the range of 96 and 3903. When F value sent is out of

range, the previous value is kept. The synthesizer band center frequency f

can be calculated as:

= 10 * C1 * (C2 + F/4000) [MHz]

The constants C1 and C2 are determined by the selected band as:

Band [MHz]

433

868

915

4. Data Rate Command

bit 15 14 13 12 11 10

7 6 5 4 3 2 1 0 POR

1 1 0 0 0 1 1

C623h

The actual bit rate in transmit mode and the expected bit rate of the received data stream in receive

mode is determined by the 7-bit parameter R (bits r6 to r0) and bit cs.

BR = 10000 / 29 / (R+1) / (1+cs*7) [kbps]

In the receiver set R according to the next function:

R= (10000 / 29 / (1+cs*7) / BR) – 1, where BR is the expected bit rate in kbps.

Apart from setting custom values, the standard bit rates from 600 bps to 115.2 kbps can be approximated

with small error.

Data rate accuracy requirements:

Clock recovery in slow mode: ΔBR/BR < 1/(29*N

bit

)

Clock recovery in fast mode: ΔBR/BR < 3/(29*N

bit

)

BR is the bit rate set in the receiver and ΔBR is the bit rate difference between the transmitter and the

receiver. N

bit

is the maximum number of consecutive ones or zeros in the data stream. It is recommended

for long data packets to include enough 1/0 and 0/1 transitions, and to be careful to use the same division

ratio in the receiver and in the transmitter.

5. Receiver Control Command

Bit 15 14 13 12 11 10 9

1 0 POR

p16

d1 d0

g1 g0

9080h

Bit 10 (p16): pin16 function select

P16 Function of pin 16

Interrupt input

VDI output

Bits 9-8 (d1 to d0): VDI (valid data indicator) signal response time setting:

Response

Fast

Medium

Slow

Always on