ata5780 ATMEL Corporation, ata5780 Datasheet - Page 11

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

3.5.2
3.5.3
9207BS–RKE–01/11
Polling Cycle Time
RKE Channel Statistic During Polling Mode
The polling cycle time determines the average current consumption in RX polling mode. This
is the time period between activation of two receiver paths. The cycle time can be pro-
grammed to be between 0ms and 4000ms and is determined when setting timer 1.
If reception path activation depends on the EEPROM configuration, the polling mode is also
started. This begins with a bit check or scanning for a valid WUP. One enhanced feature of the
device is the RF carrier detection during this phase in FSK applications. This shortens the
active time when no signal can be detected. If a bit check/WUP scan fails, the receiver goes
into sleep mode or skips into the next defined frequency channel and application channel
respectively.
This feature is only active in combination if a flexible telegram type is not supported (FTS = 0).
The receiver is able to use as many as three channels for RKE/PEG applications, thus
enhancing sensitivity and making the receiver resistant to disturbance. The RKE channel with
the best reception characteristic is constantly detected in RX polling mode and fast polling
mode. This is done by measuring and comparing the RSSI value for each RKE channel during
bit check/WUP check. The channel with the lowest RSSI signal is stored as the “best channel”
in the status register FLAG3 (BCRKE 3:1). Before transmission commences, the connected
microcontroller can read out the best channel information and is able to begin transmission on
this channel.
Note:
Follow these steps to identify the best RKE channel during polling mode:
During each polling cycle, the RKE channel with the best reception behavior is determined and
stored in a status register (FLAG 3, BCRKE2:0). This is done by reading the RSSI value dur-
ing bit check/WUP for each channel. The channel with the lowest RSSI value (= undisturbed)
is the channel with the best reception characteristic.
When using multiple RKE channels, transmitting should always start with the channel which
had the best reception characteristic in the past. This can be determined by reading the best
channel status information (FLAG3) and starting transmission on the corresponding channel.
This minimizes the response time for passive entry go applications.
The TPM and RS channel are not considered in the channel statistic!
Atmel ATA5780 [Preliminary]
11