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AS3931

Datasheet - Extende d O peratio n

10.6 Direct DATA Mode

In Direct Data Mode, the received DATA of a selected channel can be mapped to the WAKE pin. The DATA signal is the digital output of the

detector and is normally fed to the correlator, where it is scanned for the WAKE pattern (see Figure 13). To get the DATA signal at the WAKE pin,

follow the steps:

1. Enable Test Mode: set T0 = 1 in Test Mode Register

2. Select Test Mode: set T1 = 0 and T2 = 0 in Test Mode Register

3. Select Channel: set C0 and C1 in the Channel Select Register

The Direct DATA signals can also be mapped to the RSSI pin, which then becomes a digital output pin. To do this, make this step:

Select RSSI output mode digital:set C2 = 0 and C3 = 1 in the Channel Select Register

Note:

The RSSI pin is only active if the CS signal is active (CS = 1), otherwise RSSI is high Z.

10.7 Correlator Modes

Operation of the correlators can be modified regarding the error tolerances for the Zero-Half-Bits. In this case, the number of Zero-Half-Bits that

is allowed to be invalid can be set from 0 to 2. Please take into account that an increased error tolerance also reduces the immunity against

parasitic wakeups (WAKE detection when no data has been sent, due to noise or interferences).

10.8 Threshold Adaptation Filter Time Constant

Bit M4 is used to switch between a large and a small

τ of the detector threshold adaptation filter. A large τ is recommended, because it increases

the noise margin. A small

τ can be used to improve the wake sensitivity when non-specified Wake-Patterns are used.

10.9 RSSI and WAKE Pin Modes

This table gives an overview of the different signals that can be mapped to the RSSI and WAKE pin and how to program it.

Table 29. RSSI/WAKE-Pin Modes

Mode

CS

C3

C2

C1

C0

T0

T2

T1

WAKE-Pin: WAKE

X

X

X

X

X

0

X

X

WAKE-Pin: DATA1

X

X

X

0

0

1

0

0

WAKE-Pin: DATA2

X

X

X

0

1

1

0

0

WAKE-Pin: DATA3

X

X

X

1

0

1

0

0

WAKE-Pin: WAKE1

X

X

X

0

0

1

0

1

WAKE-Pin: WAKE2

X

X

X

0

1

1

0

1

WAKE-Pin: WAKE3

X

X

X

1

0

1

0

1

RSSI-Pin: WAKE

1

1

0

1

1

X

X

X

RSSI-Pin: DATA1

1

1

0

0

0

X

0

0

RSSI-Pin: DATA2

1

1

0

0

1

X

0

0

RSSI-Pin: DATA3

1

1

0

1

0

X

0

0

RSSI-Pin: WAKE1

1

1

0

0

0

X

0

1

RSSI-Pin: WAKE2

1

1

0

0

1

X

0

1

RSSI-Pin: WAKE3

1

1

0

1

0

X

0

1