ata5780 ATMEL Corporation, ata5780 Datasheet - Page 16

• Manufacturer Part Number: ata5780
• Description: Uhf Ask/fsk Receiver
• Manufacturer: ATMEL Corporation

4.3.2.2
16
Atmel ATA5780 [Preliminary]
Rx Buffer
This block has two outputs:
The symbol-based filter needs DC compensation which is performed by a feedback loop. This
loop is invoked a certain time after an edge at the data slicer output has been detected. Then
the compensation value is held until the next edge. The control signal DMHx = 0 limits this
hold sequence to the duration of three symbols.
Clock Recovery
A recovered clock based on detected edges is provided for sampling the filtered signal. The
start sequence of a telegram is used to match to the data/symbol rate. The initial symbol rate
is obtained from the DMDRA/DMDRB register.
RSSI (Digital)
The RSSI is calculated from the magnitude of the baseband signal and corrected by the gain
of the channel filter. Depending on the setting of DMDRA/DMDNA (data rate path A), a num-
ber of 2DMDNA raw samples are put together and an average value built. The peak value
from these results is held and stored to the RSSI register. The read process for the RSSI value
resets the max-hold circuit.
Symbol Check
This block checks the incoming signal quality needed to control the receiver.
There are four checks which generate a pass or fail signal:
An OK signal is generated if there is no fail during a number of symbols/bits, which can be
programmed.
Two reception buffers are available. They are connected to the reception path A and B data
outputs. This allows simultaneous reception of both modulation types or reception of the same
modulation type with different data rate settings (TPM, RKE). Each buffer has its own interrupt
for AVR
read out, it is overwritten by the following byte.
A 32-byte receive buffer is available in the receiver and can be used for data reception. When
starting RX mode the RX buffer pointer is set to the initial values (reset).
• Manchester matched (MANx)
• Symbol-based (TRPx also available to ext. pin)
1. Carrier check (FSK only) is derived from the FSK demodulator (similar to a lock
2. Modulation amplitude check (signal out of the post detection filter)
3. Symbol timing check (compares the signal edge positions in relation to clock
4. Manchester check (checks if the sampled symbols conform with Manchester code)
detect)
recovery)
®
wake-up to allow data read-out before the next byte is received. If the data is not
9207BS–RKE–01/11