ata5780 ATMEL Corporation, ata5780 Datasheet - Page 8

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

3.4.2
3.4.3
3.4.4
3.4.5
3.4.6
3.4.6.1
8
Atmel ATA5780 [Preliminary]
Modulation in Receiving Mode
Data Rate
RX Error Handling
Controlling an External LNA
Protocol and Telegram Handling
Simple Telegram (FTS = 0)
In transparent mode, after the receiver recognizes the valid wake-up criterion the received
data stream and a corresponding data clock are generated on TMDO and TMDO_CLK
directly. The wake-up criteria must be set in the EEPROM. The first criterion is detection of
BitCheck and the start bit. This is the criterion for a standard telegram format. The second one
is the wake-up pattern and the SFID, which are part of a flexible telegram format. If the two
demodulator reception paths (path A and path B) are activated, the signals generated on pin
TMDO and TMDO_CLK come from the path which has recognized the first successfully
wake-up criterion.
For analysis and monitoring purposes the IC offers another type of transparent signal. The pin
TRPA and TRPB can be used for this purpose. The raw data received is generated at the
selected pin.
Atmel
well as ASK and FSK modulation types. The novel feature of this Atmel receiver is its ability to
receive GFSK modulated telegrams.
Using the buffer mode the receiver supports the data rate from 0.5kBps to 20kBps in Man-
chester coding, whereas in NRZ coding the supported data rate range is between 1kBps and
40kBps.
One of the important parameters for system sensitivity is the data rate tolerances. Atmel
ATA5780 supports the receiving of signal with a data rate tolerance of up to ±10% without any
sensitivity loss. The guaranteed sensitivity loss is just 1dB for data rate tolerance of up to
±20%.
This section describes the behavior of the device if a bit error or an ID scan error occurs during
the reception process. The discussed condition in this section is the receiving mode's state
after the successful detection of an SFID or start bit. The RX error handlings can be set to
receiver configuration 6 (TC6) in the EEPROM.
Depending on the system requirement, higher reception path sensitivity may be required. An
external low noise amplifier should be used to boost sensitivity. This device offers an RXAC-
TIVE output pin which can be used to bias the external LNA. Basically, the pin shows the
active time of the receiver path and can supply a maximum of 4mA current consumption. The
polarity of the RX_ACTIVE pin can be set in the EEPROM (IRQ/event configuration).
A simple telegram consists of a preamble, start bit and data stream. The start bit is the part of
the first data byte which must be different from the preamble sequence. If the preamble
sequence is “0000…” the start bit must be “1”. Conversely, the start bit must be “0” if the pre-
amble sequence is “1111…”.
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ATA5780 supports the typical modulation types in short-range device applications, as
9207BS–RKE–01/11