Datasheet

Figure 46-16. Manchester Encoded Characters RF Transmission
LNA
VCO
RF filter
Demod
Control
bi-dir
line
PA
RF filter
Mod
VCO
Control
Manchester
Decoder
Manchester
Encoder
USART
Receiver
USART
Emitter
ASK/FSK
Upstream Receiver
ASK/FSK
Downstream Transmitter
Upstream
Emitter
Downstream
Receiver
Serial
Configuration
Interface
f
UP
Frequency Carrier
f
DOWN
Frequency Carrier
The USART peripheral is configured as a Manchester encoder/decoder. Looking at the downstream communication
channel, Manchester encoded characters are serially sent to the RF emitter
. This may also include a user defined
preamble and a start frame delimiter. Mostly, preamble is used in the RF receiver to distinguish between a valid data
from a transmitter and signals due to noise. The Manchester stream is then modulated. See Figure 46-17 for an
example of ASK modulation scheme. When a logic one is sent to the ASK modulator, the power amplifier, referred to
as PA, is enabled and transmits an RF signal at downstream frequency. When a logic zero is transmitted, the RF
signal is turned off. If the FSK modulator is activated, two different frequencies are used to transmit data. When a
logic one is sent, the modulator outputs an RF signal at frequency F0 and switches to F1 if the data sent is a zero.
See Figure 46-18.
From the receiver side, another carrier frequency is used. The RF receiver performs a bit check operation examining
demodulated data stream. If a valid pattern is detected, the receiver switches to Receiving mode. The demodulated
stream is sent to the Manchester decoder. Because of bit checking inside RF IC, the data transferred to the
microcontroller is reduced by a user-defined number of bits. The Manchester preamble length is to be defined in
accordance with the RF IC configuration.
Figure 46-17. ASK Modulator Output
Manchester
Encoded Data
Default Polarity
Unipolar Output
TXD
ASK Modulator Output
Upstream Frequency F0
NRZ Stream
1 0 0 1
SAM E70/S70/V70/V71 Family
Universal Synchronous Asynchronous Receiver T
ransc...
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echnology Inc.
Datasheet
DS60001527D-page 1192