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AS3932

8.2.2.3 ON/OFF mode (Low Power mode 2)

All active channels are on at the same time but not for the whole time (time slot T is defined as 1ms). An on-off duty-ratio is defined. This duty

ratio is programmable see R4<7:6>.

Figure 12. ON/OFF Mode

For each of these sub modes it is possible to enable a further feature called Artificial Wake-up. The Artificial Wake-up is a counter based on the

used RTC. Three bits define a time window see R8<2:0>. If no activity is seen within this time window the chip will produce an interrupt on the

WAKE pin that lasts 128 µs. With this interrupt the microcontroller (µC) can get feedback on the surrounding environment (e.g. read the false

wakeup register, see Correlator register R13<7:0>) and/or take actions in order to change the setup.

8.2.3 Preamble Detection / Pattern Correlation

The chip can go in to this mode after detecting a LF carrier only if the data correlator function is enabled see R1<1>. The correlator searches

first for preamble frequency (constant frequency of Manchester clock defined according to bit-rate transmission) and then for data pattern.

If the pattern is matched the wake-up interrupt is displayed on the WAKE output and the chip goes in Data receiving mode. If the pattern fails the

internal wake-up (on all active channels) is terminated and no IRQ is produced.

8.2.4 Data Receiving

The user can enable this mode allowing the pattern correlation or just on the base of the frequency detection. In this mode the chip can be

retained a normal OOK receiver. The data is provided on the DAT pin and in case the Manchester decoder is enabled see R1<3>, the recovered

clock is present on the CL_DAT. It is possible to put the chip back to listening mode either with a direct command (CLEAR_WAKE (see Table 12))

or by using the timeout feature. This feature automatically sets the chip back to listening mode after a certain time R7<7:5>.

8.3 System and Block Specification

8.3.1 Register Table

Table 6. Register Table

7

6

5

4

3

2

1

0

R0

n.a.

ON_OFF

MUX_123

EN_A2

EN_A3

EN_A1

PWD

R1

ABS_HY

AGC_TLIM

AGC_UD

ATT_ON

EN_MANCH

EN_PAT2

EN_WPAT

EN_RTC

R2

S_ABSH

W_PAT_T<1:0>

Reserved

S_WU1<1:0>

R3

HY_20m

HY_POS

FS_SLC<2:0>

FS_ENV<2:0>

R4

T_OFF<1:0>

R_VAL<1:0>

GR<3:0>

R5

TS2<7:0>

R6

TS1<7:0>

R7

T_OUT<2:0>

T_HBIT<4:0>

time

time

time

Channel1

Channel2

Channel3

time

Presence

of carrier

t0

t0+T

2*t0

2*t0+T

3*t0