SAM3SD8B Atmel Corporation, SAM3SD8B Datasheet - Page 719

• Manufacturer Part Number: SAM3SD8B
• Manufacturer: Atmel Corporation

Figure 32-17. Manchester Encoded Characters RF Transmission
Figure 32-18. ASK Modulator Output
11090A–ATARM–10-Feb-12
11090A–ATARM–10-Feb-12
Uptstream Frequency F0
ASK Modulator
unipolar output
default polarity
NRZ stream
Manchester
Downstream
Upstream
encoded
Output
Emitter
Receiver
data
Fdown frequency Carrier
Fup frequency Carrier
Txd
1
The USART module is configured as a Manchester encoder/decoder. Looking at the down-
stream 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, pre-
amble 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
ple 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 1 is sent, the modulator out-
puts an RF signal at frequency F0 and switches to F1 if the data sent is a 0. See
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.
0
downstream transmitter
Upstream Receiver
RF filter
control
RF filter
control
Demod
VCO
VCO
ASK/FSK
LNA
Mod
PA
ASK/FSK
0
bi-dir
line
Configuration
Manchester
Manchester
decoder
encoder
Interface
Serial
Figure 32-18
SAM3S8/SD8
SAM3S8/SD8
1
Receiver
USART
USART
Emitter
Figure
for an exam-
32-19.
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