STW5098T datasheet(26/85 Pages) STMICROELECTRONICS

26 / 85 page

Functional description

STw5098

26/85

Attack and Decay time constants are related to the AD data rate (see bits AGCATT and

AGCDEL in CR34).

4.16

Interrupt request: IRQ pins

On each entity of the STw5098, the interrupt request feature can signal to a control device

the occurrence of particular events on each entity. Two control registers are used to choose

the behavior of IRQ pin: the first is a Status/Event Register (CR32), where bits can

represent the status of an internal function (i.e. a voltage is above or below a threshold) or

an event (i.e. a voltage changed crossing a threshold); the second is a Mask Register

(CR31) where if a bit in the mask is set to 1 then the corresponding bit in the Status/Event

On each entity, the IRQ pin is always active low. At VCC power up an interrupt request is

generated by the Power-On-Reset circuit that sets to 1 bits PORMSK in CR31 and POREV

in CR32. After this event the PORMSK bit should be cleared by the user and bit IRQCMOS

in CR33 should be set according to the application (open drain or CMOS).

When an IRQ event occurs and SPI control interface is selected with no serial output pin it is

still possible to identify the event (and relative status) that generated the interrupt request.

This can be done by setting the IRQ mask/enable bits (in CR31) one at the time (with

successive writings) and reading the IRQ pin status. A simple example of this is the headset

plug-in detection: at first we set bit HSDETMSK=1 in CR31 (with all the other bits set to 0). If

there is an interrupt request then we set HSDETMSK=0 and HSDETEN=1, so we can read

the HSDET status at IRQ pin. Then we read CR32 to clear its content (even if no data is

sent out).

4.17

Headset plug-in and push-button detection

Each entity of the STw5098 can detect the plug-in of a microphone connector and the

press/release event of a call/answer push-button. An application example can be found

below, while specifications can be found in

Section 10.4 on page 64.

Figure 4.

Plug-in and push-button detection application note

Call/Answer Button

µF

1.5k

Ω

VCCA

Ω

200nF

AUX1L

AUX1R

CAPMIC

HDET

200nF

STw5095

Generic Connector

From driver

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