Rf12 – Rainbow Electronics RF12 User Manual
Page 19
RF12
Note:
The transceiver is in receive (RX) mode when bit er is set using the Power Management
Command
9. AFC
Command
bit
15 14 13 12 11
10
9
8
7 6 5 4 3 2
1 0 POR
1 1 0 0 0 1 0
0
a1
a0
rl1
rl0
st
fi
oe
en
C4F7h
Bit 7-6 (a1 to a0): Automatic operation mode selector:
a1 a0
0 0 Auto mode off (Strobe is controlled by microcontroller)
0 1 Runs only once after each power-up
1 0 Keep the foffset only during receiving (VDI=high)
1 1 Keep the foffset value independently from the state of the VDI signal
Bit 5-4 (rl1 to rl0): Range limit. Limits the value of the frequency offset register to the next values:
rl1
rl0
Max deviation
0
0
No restriction
0
1
+15 f
res
to -16 f
res
1
0
+7 f
res
to -8 f
res
1
1
+3 f
res
to -4 f
res
Bit 3 (st): Strobe edge, when st goes to high, the actual latest calculated frequency error is stored into the
offset register of the AFC block.
Bit 2 (fi): Switches the circuit to high accuracy (fine) mode. In this case, the processing time is about twice
longer, but the measurement uncertainty is about the half.
f :
res
315, 433 MHz bands: 2.5 kHz
868 MHz band: 5 kHz
915 MHz band: 7.5 kHz
Bit 1 (oe): Enables the frequency offset register. It allows the addition of the offset register to the
frequency control word of the PLL.
Bit 0 (en): Enables the calculation of the offset frequency by the AFC circuit.
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