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AS3930

Datasheet - Detailed Descr i p ti on

8.6.2 Single Pattern Detection

Figure 18 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 is set to high 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.

Figure 18. Wake-up Protocol Overview with Single Pattern Detection

Table 22. Preamble Requirements in Standard Mode, Scanning Mode and ON/OFF Mode

Bit Rate (bit/s)

Maximum Duration of the Carrier Burst in Standard

Mode and Scanning Mode (ms)

Maximum Duration of the Carrier Burst in ON/OFF

Mode (ms)

8192

1.95

10

6552

2.44

10

5460

2.93

10

4680

3.41

10

4096

3.90

10

3640

4.39

10

3276

4.88

10

2978

5.37

10

2730

5.86

10

Carrier Burst

Preamble

Pattern

Data

WAKE

Clear_wake

DAT

1-bit Preamble

Preamble > 4-bit duration

Preamble + Pattern < 40-bit duration

Carrier Burst>360 us

Carrier Burst<16-bit duration