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AS3930

Data Sheet - D e t a i l e d D e s c r i p t i o n

8.7 Wakeup Protocol - Carrier Frequency 125 kHz

8.7.1 Without pattern detection (Manchester decoder disabled)

Figure 17. Wakeup Protocol Overview without Pattern Detection (only carrier frequency detection, Manchester decoder disabled)

In case the data correlation is disabled (R1<1>=0) the AS3930 wakes up upon detection of the carrier frequency only as shown in Figure 17. In

order to ensure that AS3930 wakes up the carrier burst has to last longer than 550 µs. To set AS3930 back to listening mode there are two

possibilities: either the microcontroller sends the direct command clear_wake via SDI or the time out option is used (R7<7:5>). In case the latter

is chosen,AS3930is automatically set to listening mode after the time defined in T_OUT (R7<7:5>), counting starts at the low-to-high WAKE

edge on the WAKE pin.

8.7.2 Single Pattern Detection (Manchester decoder disabled)

The Figure 18 shows the wakeup protocol in case the pattern correlation is enabled (R1<1>=1) for a 125 kHz carrier frequency. The initial carrier

burst has to be longer than 550 µs and can last maximum 16 bits (see bit rate definition in Table 18). If the ON/OFF mode is used (R1<5>=1), the

minimum value of the maximum carrier burst duration is limited to 10 ms. This is summarized in Table 21. In case the carrier burst is too long the

internal wakeup will be set back to low and the false wakeup counter (R13<7:0>) will be incremented by one.

The carrier burst must be followed by a preamble (0101... modulated carrier with a bit duration defined in Table 18) and the wakeup pattern

stored in the registers R5<7:0> and R6<7:0>. The preamble must have at least 4 bits and the preamble duration together with the pattern should

not be longer than 40 bits. If the wakeup pattern is correct the signal on the WAKE pin is set to high and the data transmission can get started. To

set the chip back to listening mode the direct command clear_false, as well as the time out option (R7<7:5>) can be used.