Atmel ARM-Based Evaluation Kit AT91SAM9N12-EK AT91SAM9N12-EK Data Sheet
Product codes
AT91SAM9N12-EK
768
SAM9N12/SAM9CN11/SAM9CN12 [DATASHEET]
11063K–ATARM–05-Nov-13
When the start frame delimiter is a sync pattern (ONEBIT field to 0), both command and data delimiter are supported. If a
valid sync is detected, the received character is written as RXCHR field in the US_RHR register and the RXSYNH is
updated. RXCHR is set to 1 when the received character is a command, and it is set to 0 if the received character is a
data. This mechanism alleviates and simplifies the direct memory access as the character contains its own sync field in
the same register.
valid sync is detected, the received character is written as RXCHR field in the US_RHR register and the RXSYNH is
updated. RXCHR is set to 1 when the received character is a command, and it is set to 0 if the received character is a
data. This mechanism alleviates and simplifies the direct memory access as the character contains its own sync field in
the same register.
As the decoder is setup to be used in unipolar mode, the first bit of the frame has to be a zero-to-one transition.
40.7.3.5 Radio Interface: Manchester Encoded USART Application
This section describes low data rate RF transmission systems and their integration with a Manchester encoded USART.
These systems are based on transmitter and receiver ICs that support ASK and FSK modulation schemes.
These systems are based on transmitter and receiver ICs that support ASK and FSK modulation schemes.
The goal is to perform full duplex radio transmission of characters using two different frequency carriers. See the
configuration in
configuration in
.
Figure 40-17. Manchester Encoded Characters RF Transmission
The USART module 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
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
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
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.
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.
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