587
32072H–AVR32–10/2012
AT32UC3A3
Figure 25-50. Manchester Error
25.6.16.3
Radio Interface: Manchester Endec Application
This section describes low data rate, full duplex, dual frequency, RF systems integrated with a
Manchester endec, that support ASK and/or FSK modulation schemes. See
.
Figure 25-51. Manchester Encoded Characters RF Transmission
To transmit downstream, encoded data is sent serially to the RF modulator and then through
space to the RF receiver. To receive, another frequency carrier is used and the RF demodulator
does a bit-checking search for valid patterns before it switches to a receiving mode and forwards
data to the decoder. Defining preambles to help distinguish between noise and valid data has to
be done in conjunction with the RF module, and may sometimes be filtered away from the endec
stream. Using the ASK modulation scheme, a one is transmitted as an RF signal at the down-
stream frequency, while a zero is transmitted as no signal. See
. The FSK
modulation scheme uses two different frequencies to transmit data. A one is sent as a signal on
one frequency, and a zero on the other. See
Manchester
encoded
data
Txd
SFD
Preamble Length
is set to 4
Elementary character bit time
Manchester
Coding Error
detected
sampling points
Preamble subpacket
and Start Frame Delimiter
were successfully
decoded
Entering USART character area
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
Fup frequency Carrier
Fdown frequency Carrier
Содержание AT32UC3A3128
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Страница 991: ...991 32072H AVR32 10 2012 AT32UC3A3 Figure 37 3 VFBGA 100 package drawing...