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AS3932

Datasheet - Detailed Descr i p ti on

8.6.1 Without Pattern Detection

Figure 18. Wake-up Protocol Overview without Pattern Detection (only carrier frequency detection)

In case the data correlation is disabled (R1<1>=0) the AS3932 wakes up upon detection of the carrier frequency only as shown in Figure 18. In

order to ensure that AS3932 wakes up the carrier burst has to last longer than 550 µs. To set AS3932 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, AS3932 is 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.

8.6.2 Single Pattern Detection

The Figure 19 shows the wake-up 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 19). 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 22. In case the carrier

burst is too long the internal wake-up will be set back to low and the false wake-up 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 19) and the wake-up 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 wake-up pattern is correct, the signal on the WAKE pin goes high one bit after the end of the pattern and the data

transmission can get started. To set the chip back to listening mode the direct command clear_wake, as well as the time out option (R7<7:5>)

can be used.

Carrier Burst

Data

Carrier Burst > 550 us

WAKE

Clear_wake

DAT