Atmel Xplained Pro Evaluation Kit ATSAM4E-XPRO ATSAM4E-XPRO Data Sheet
Product codes
ATSAM4E-XPRO
901
SAM4E [DATASHEET]
Atmel-11157D-ATARM-SAM4E16-SAM4E8-Datasheet_12-Jun-14
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
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
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 1 is sent, the modulator outputs an RF signal at frequency F0 and switches to F1 if
the data sent is a 0. See
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 outputs 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.
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 38-18. ASK Modulator Output
Figure 38-19. FSK Modulator Output
38.7.3.6 Synchronous Receiver
In synchronous mode (SYNC = 1), the receiver samples the RXD signal on each rising edge of the baud rate clock.
If a low level is detected, it is considered as a start. All data bits, the parity bit and the stop bits are sampled and the
receiver waits for the next start bit. Synchronous mode operations provide a high-speed transfer capability.
If a low level is detected, it is considered as a start. All data bits, the parity bit and the stop bits are sampled and the
receiver waits for the next start bit. Synchronous mode operations provide a high-speed transfer capability.
Configuration fields and bits are the same as in asynchronous mode.
illustrates a character reception in synchronous mode.
Manchester
encoded
data
default polarity
unipolar output
Txd
ASK Modulator
Output
Uptstream Frequency F0
NRZ stream
1
0
0
1
Manchester
encoded
data
default polarity
unipolar output
Txd
FSK Modulator
Output
Uptstream Frequencies
[F0, F0+offset]
NRZ stream
1
0
0
1