RFM12B_15 Datasheet, PDF (15/41 Pages) List of Unclassifed Manufacturers – Universal ISM Band FSK Transceiver

Description of the Control Commands
RFM12B
1. Configuration Setting Command
Bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
1 0 0 0 0 0 0 0 el ef b1 b0 x3 x2 x1 x0
POR
8008h
Bit el enables the internal data register.
Bit ef enables the FIFO mode. If ef = 0 then DATA (pin 6) and DCLK (pin 7) are used for data and data clock output.
b1 b0
00
01
10
11
Frequency Band
Reserved
433
868
915
2. Power Management Command
x3 x2 x1 x0 Crystal Load Capacitance [pF]
0000
8.5
0001
9.0
0010
9.5
0011
10.0
…
1110
15.5
1111
16.0
Bit 15 14 13 12 11 10 9
1000001
876543210
0 er ebb et es ex eb ew dc
POR
8208h
Bit Function of the control bit
er
Enables the whole receiver chain
ebb The receiver baseband circuit can be separately switched on
et
Switches on the PLL, the power amplifier, and starts the
transmission (If TX register is enabled)
es
Turns on the synthesizer
ex
Turns on the crystal oscillator
eb
Enables the low battery detector
ew Enables the wake-up timer
dc
Disables the clock output (pin 8)
Related blocks
RF front end, baseband, synthesizer, crystal oscillator
Baseband
Power amplifier, synthesizer, crystal oscillator
Synthesizer
Crystal oscillator
Low battery detector
Wake-up timer
Clock output buffer
The ebb, es, and ex bits are provided to optimize the TX to RX or RX to TX turnaround time.
The RF frontend consist of the LNA (low noise amplifier) and the mixer. The synthesizer block has two main components: the VCO
and the PLL. The baseband section contains the baseband amplifier, low pass filter, limiter and the I/Q demodulator.
To decrease TX/RX turnaround time, it is possible to leave the baseband section powered on. Switching to RX mode means disabling
the PA and enabling the RF frontend. Since the baseband block is already on, the internal startup calibration will not be performed,
the turnaround time will be shorter.
The synthesizer also has an internal startup calibration procedure. If quick RX/TX switching needed it may worth to leave this block
on. Enabling the transmitter using the et bit will turn on the PA, the synthesizer is already up and running. The power amplifier almost
immediately produces TX signal at the output.
The crystal oscillator provides reference signal to the RF synthesizer, the baseband circuits and the digital signal processor part.
When the receiver or the transmitter part frequently used, it is advised to leave the oscillator running because the crystal might need
a few milliseconds to start. This time mainly depends on the crystal parameters.
It is important to note that leaving blocks unnecessary turned on can increase the current consumption thus decreasing the battery
life.
15
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