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Revision 1.2

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AS3932

Figure 15. Reading of Single Register Byte

Figure 16. Send Direct COMMAND byte

8.4 Channel Amplifier and Frequency Detector

Each of the 3 channels consists of a variable gain amplifier, an automatic gain control and a frequency detector. The latter detects the presence

of a carrier. As soon as the carrier is detected the AGC is enabled, the gain of the VGA is reduced and set to the right value and the RSSI can be

displayed.

It is possible to enable/disable individual channels, in case not all three channels are needed. This enables to reduce the current consumption by

1.5 µA (typ.) per channel.

8.4.1 Frequency Detector / AGC

The frequency detection uses the RTC as time base. In case the internal RC oscillator is used as RTC, it must be calibrated, but the calibration

is guaranteed for a 32.768 kHz crystal oscillator only. The frequency detection criteria can be tighter or more relaxed according to the setup

described in R2<1:0>(see Table 13).

Table 13. Tolerance Settings for Wakeup

R2<1>

R2<0>

Tolerance

00

relaxed

0

1

tighter (medium)

1

0

stringent

11

Reserved

CS

SCLK

SDI

0

1

A5

A4

A3

A2

A1

A0

X

X

SCLK rais ing

edge Data is

mov ed f rom

Address

<A5-A0>

CS falling

edge signals

end of READ

Mode

01 pattern

indicat es

READ Mode

D4

D3

D2

D1

D0

D7

D6

X

X

SDO

SCLK raising

edge Dat a is

transfered from

µC

SCLK

f alling edge

Dat a is

sampled

SCLK f alling

edge Dat a is

transf ered to

µC

D5