AS3932-BTST austriamicrosystems, AS3932-BTST Datasheet - Page 27

• Manufacturer Part Number: AS3932-BTST
• Description: IC RF PROGRAM 16-TSSOP
• Manufacturer: austriamicrosystems

Specifications of AS3932-BTST

• Rf Type: Read / Write
• Frequency: 110kHz ~ 150kHz
• Features: RSSI Equipped
• Package / Case: 16-TSSOP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: AS3932-BTSTTR

AS3932
Datasheet - D e t a i l e d D e s c r i p t i o n
8.6.3 Single Pattern Detection (Manchester decoder enabled)
The
for a 125 kHz carrier frequency. The initial carrier burst has to be at least 42 Manchester symbols long and has to be followed by a separation bit
(one bit of no-carrier). The carrier burst must be followed by a minimum 4 Manchester symbol preamble (10101010) and the pattern stored in the
R5<7:0> and R6<7:0>. The preamble can only be made up by integer Manchester symbol and the preamble duration together with the pattern
should not be longer than 40 bits. If the pattern is correct the signal on the WAKE pin is set to high, the data are internally decoded and the
Manchester clock is recovered. To set the AS3932 back to listening mode the direct command clear_false or the time out option (R7<7:5>) can
be used.
In case the On/OFF mode is enabled the Manchester decoder can not be used.
Figure 21. Wakeup Protocol Overview with Single Pattern Detection (Manchester decoder enabled)
8.7 False Wakeup Register
The wakeup strategy in the AS3932 is based on 2 steps:
If there is a disturber or noise capable to overcome the first step (frequency detection) without producing a valid pattern, then a false wakeup call
happens.Each time this event is recognized a counter is incremented by one and the respective counter value is stored in a memory cell (false
wakeup register). Thus, the microcontroller can periodically look at the false wakeup register, to get a feeling how noisy the surrounding
environment is and can then react accordingly (e.g. reducing the gain of the LNA during frequency detection, set the AS3932 temporarily to
power down etc.), as shown in the
environment and thus avoid false wakeup events.
Most wakeup receivers have to deal with environments that can rapidly change. By periodically monitoring the number of false wakeup events it
is possible to adapt the system setup to the actual characteristics of the environment and enables a better use of the full flexibility of AS3932.
Note: If the Manchester decoder is enabled, the false wakeup register is not able anymore to store the false wakeup events.
www.austriamicrosystems.com/LF-Receiver/AS3932
Clear_wake
Figure
WAKE
1. Frequency Detection: in this phase the frequency of the received signal is checked.
2. Pattern Correlation: here the pattern is demodulated and checked whether it corresponds to the valid one.
shows the wakeup protocol in case both the pattern correlation and the Manchester decoder are enabled (R1<1>=1 and R1<3>=1)
Carrier Burst > 42
symbols duration
Carrier Burst
Separation bit
Figure
Preamble + Pattern < 40 bit duration
Preamble > 4 symbol (8 bits)
22. The false wakeup counter is a useful tool to quickly adapt the system to any changes in the noise
Preamble
Revision 1.4
Pattern
Data
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