AS3933 datasheet(47/64 Pages) AMSCO

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[v1-08] 2015-Sep-02

AS3933 − Detailed Description

If the carrier burst is shorter than what has been specified in

the Figure 52, then the frequency detection is not guaranteed.

In order to fulfill the protocol the carrier burst must be shorter

than 155 periods of the clock generator (crystal oscillator or

RCO or external clock). The carrier burst must be followed by a

separation bit and at least 6 bits preamble (101010). The

separation bit must last as half Manchester symbol (see

paragraph Pattern: Bit and Symbol Definition in Manchester

Code). The preamble and the pattern cannot be longer than 30

symbols in sum in case 16-bit pattern detection is enabled and

46 symbols if the 32-bit pattern detection is enabled.

In case the ON/OFF option is enabled (R0<5>=1) the minimum

duration of the carrier burst must be prolonged by the OFF time

defined in the R4<7:6>.

Should the carrier burst be longer than what is defined in the

Figure 52 or the number of preamble bits longer than what has

been specified above a false wake-up event might be recorded

in the register R13<7:0>.

If the Scan Mode be enabled (R0<4>=1) the minimum duration

of the carrier burst is defined in the Figure 53.

Figure 53:

Minimum Duration of the Carrier Burst in Case the Scanning

Mode is Enabled

Operating Frequency

Range [kHz]

Minimum Duration of the

Carrier Burst

95-150

80·Tclk+16Tcarr

65-95

92·Tclk+16Tcarr

40-65

180·Tclk+16Tcarr

23-40

224Tclk+16Tcarr

15-23

220·Tclk+8Tcarr

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