Atmel SAM4L Xplained Pro Evaluation Kit Atmel ATSAM4L-XPRO ATSAM4L-XPRO Data Sheet

42023E–SAM–07/2013

Figure 24-51. Manchester Error

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 24-52. 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 

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