AT91SAM9G20_1 Datasheet, PDF (477/832 Pages) ATMEL Corporation – AT91 ARM Thumb Microcontrollers

AT91SAM9G20 Preliminary
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.
Figure 32-18. ASK Modulator Output
1
0
0
1
NRZ stream
Manchester
encoded
data
default polarity
Txd
unipolar output
ASK Modulator
Output
Uptstream Frequency F0
Figure 32-19. FSK Modulator Output
1
0
0
1
NRZ stream
Manchester
encoded
data
Txd
default polarity
unipolar output
FSK Modulator
Output
Uptstream Frequencies
[F0, F0+offset]
32.6.3.7
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.
Configuration fields and bits are the same as in asynchronous mode.
Figure 32-20 illustrates a character reception in synchronous mode.
6384D–ATARM–04-May-09
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