ata5780 ATMEL Corporation, ata5780 Datasheet - Page 10

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

3.4.8
3.5
3.5.1
10
Polling Mode
Atmel ATA5780 [Preliminary]
RSSI Measurement
Overview
Note:
The receiver offers digital RSSI values and measures the RSSI value of the received signal at
regular intervals. This feature works in RX mode only. The measurement intervals must be set
in the RSSI configuration of the EEPROM.
The measurement interval can be configured to be between 0.25ms and 4.0ms. The mea-
sured RSSI values are stored in a 32-byte RSSI buffer.
The RSSI sampling is started the moment the start bit or SFID is successfully recognized. In
case the RX mode is restarted or when the ID check fails during polling, the RSSI buffer
pointer is set to the initial values. Depending on a defined buffer fill level the device can gener-
ate an event or interrupt which can be used to trigger the microcontroller. The following
receiver states allow the RSSI request to be activated:
The RSSI can be used in both RX buffer and Rx transparent mode.
As a part of the flexible telegram support (FTS = 1) the Atmel
minimum and maximum RSSI value to be defined as additional wake-up criteria.
The minimum and maximum values are stored in SRAM with the initial values of 0x00 (min)
and 0xFF (maximum). With this initialization there is no restricted area and all telegrams with a
valid WUP check are accepted.
The use of polling mode in the Atmel ATA5780 reduces current consumption. In this mode the
receiver path alternates between active and sleep mode. During the short active mode the
device scans for the valid telegram. During a relative short active period the wake-up (WUP)
logic verifies the incoming signal by checking the telegram for a valid wake-up pattern or bit
check. The device is able to detect two different telegram types. The first one is the standard
telegram type for which the wake-up criteria are the bit check and start bit. The second tele-
gram type is a flexible telegram which is validated using a wake-up criteria pattern, SFID, etc.
If no valid telegram is detected, the receiver returns to sleep mode. The device stays in active
mode if a valid telegram is detected.
The autonomous polling scenario of the Atmel ATA5780 allows three different application
types to be combined: Remote Keyless Entry (RKE), Tire Pressure Monitoring System
(TPMS), and Remote Start (RS). The receiver path automatically scans for the valid telegrams
of the three applications. For the RKE a multi-channel system of up to three operating frequen-
cies can be used. All polling scenario settings can be selected when configuring the EEPROM.
The frequency ranges, modulation, data rate, and the wake-up criteria of the three different
application channels can be completely different. Even the polling cycle of the RKE, TPMS,
and RS system can uniquely be defined in the EEPROM. This flexibility allows the combina-
tion of three different application systems using a single device, which helps reduce system
costs.
• Demodulator_stable
• Bit/WUP check or
• RX_Mode
If a telegram with a valid ID is received the receiver automatically reverts to idle mode.
®
ATA5780 receiver allows the
9207BS–RKE–01/11