Atmel SAM4S-XPLD Atmel ATSAM4S-XPLD ATSAM4S-XPLD Hoja De Datos

 705

SAM4S [DATASHEET]

11100E–ATARM–24-Jul-13

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 

.

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.

t

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.

Configuration fields and bits are the same as in asynchronous 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