ata5780 ATMEL Corporation, ata5780 Datasheet - Page 7

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

3. Description of System Functions
3.1
3.2
3.3
3.4
3.4.1
9207BS–RKE–01/11
OFF Mode
IDLE Mode
Coding Schemes and Modulation Option
Receiving (RX) Mode
RX Transparent Mode and Buffered Mode
The purpose of this mode is to set the device in a condition with very low current consumption.
For example a current consumption of 5nA can be typically expected for a 3V application,
which is a benefit for the battery application. All the circuits of the receiver, AVCC, and DVCC
are deactivated while in this mode so that the device will not be sensitive to any RF signals or
SPI commands. Furthermore, all the ports are set as an input. To leave the mode, the receiver
must be woken up using the PWRON pin or NPWRON pins.
Most parts of the circuit are deactivated in idle mode. It is advisable to set the AVR
power-down mode in order to achieve the lowest current consumption. The Atmel
receiver provides 2 different idle modes, Idle RC and Idle XTO. For Idle RC the DVCC power
supply is active and the AVR core runs with either slow RC oscillator (SRC) or fast RC oscilla-
tor (FRC). DVCC, AVCC, and XTO are active in Idle XTO mode.
The Atmel receiver ATA5780 works with Manchester and NRZ coding for system design flexi-
bility.
application. Because of its flexibility, system designers can configure the Atmel receiver
ATA5780 using another polarity of the Manchester coding. This can be set in the EEPROM
configuration.
Figure 3-1.
The receiver’s RX mode can be started in two ways, first by using the “Start_RX_EEPROM”
SPI command. In this case the command leads the loading of all channel parameters from the
EEPROM and starts RX mode. Secondly, the RX mode starts after power on automatically as
preselected in the EEPROM. In this condition the IC automatically leaves OFF mode, checks
the receiver configuration in the EEPROM (TC2), loads all channel parameters from the
EEPROM and starts RX mode.
If the transmitter or receiver buffer mode is set, the received telegram is stored in the 32-byte
RX buffer first before it can be read via SPI command. The Atmel ATA5780’s demodulator
contains two different paths whose parameters can be set separately, e.g. the modulation type
and data rate. Both paths generally work simultaneously until the device receives initial valid
data from one of the both paths. Only this initial valid data is stored in the RX buffer. Because
the buffer is a ring buffer, a special interrupt is defined for the microcontroller (e.g., the AVR
block) so that the stored data can be read out quickly.
Figure 3-1
Manchester Coding Polarity
shows the Manchester coding polarity which is usually used in the
”0”
Atmel ATA5780 [Preliminary]
”1”
®
ATA5780
®
core to
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