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AS3931

Datasheet - Configuring the Product

9.3.1 C0, C1 (RSSI Channel Select)

Bits C0 and C1 are used to select the channel whose RSSI signal is multiplexed to the RSSI pin. In case of both bits C0 and C1 set to 1, a

bandgap voltage VBG (1.25 V) appears at the RSSI pin. After power on, channel 1 is selected.

9.3.2 C2, C3 (RSSI Output Mode)

Bits C2 and C3 define the RSSI pin function.

Note:

The RSSI pin function also depends on the signal CS. If CS = 0, the RSSI pin is always in the high impedance state. This is also the

case after power on.

The WAKE or single WAKE function is selected together with bits T0 – T2 and C0 – C1. For more information see Extended Operation

on page 24

9.3.3 C4 (Channel Attenuator)

When bit C4 is set, a resistor (app. 1.5 k

Ω) is connected across the differential inputs of each channel. This resistor reduces the Q-factor of the

antenna resonant circuit; therefore the received signal is reduced too. The amount of damping depends on the Q-factor of the antenna circuit.

Table 11. Register Address

Bit

Value

A0

1

A1

0

Table 12. C0, C1 Bit Mode

C0

C1

Mode

0

0

Channel 1

1

0

Channel 2

0

1

Channel 3

1

1

VBG (T0=0), WAKE (T0=1)

Table 13. C2, C3 Bit Mode

C2

C3

RSSI Pin Function

0

0

high Z

10

Analog output: RSSI of selected channel or

VBG

01

Digital output: WAKE,

single WAKE or DATA

1

1

not used

Table 14. C4 Bit Mode

C4

Mode

0

Input attenuators disabled

1

Input attenuators enabled