STV8247T datasheet(44/149 Pages) STMICROELECTRONICS

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Additional Controls and Flag

STV82x7

44/149

Additional Controls and Flag

This logic contains:

● the headphone detection,

● the IRQ generation, signal to be output to the MCU,

● the I²C bus expander output pin.

9.1

Headphone Detection

For headphone, the HP_DET input can be used to automatically mute the Loudspeakers and

Subwoofer outputs when the HP_LS_MUTE bit is set in register HEADPHONE_CONFIG (active

low). When a headphone is detected (the HP_DET pin is set to 0) and the Mute function is enabled.

Each change on the HP_DET pin generates an IRQ request to the microprocessor on the IRQ pin.

9.2

IRQ Generation

Four IRQs are generated by the STV82x7. On each IRQ generation, the IRQ pin is set to 1. The

pending IRQ status must be read at the I²2S address 81h and the acknowledge is done by writing 0

to this register.

The four availables IRQs are:

IRQ0: The identified TV sound standard is displayed in register AUTOSTD_STATUS. Each change

in the detected standard is flagged to the host system via hardware pin IRQ. The flag must be reset

by re-programming the IRQ bit in register AUTOSTD_CTRL and then checking the detected

standard status by reading registers AUTOSTD_STATUS, NICAM_STAT, and ZWT_STAT.

IRQ1: This IRQ is enabled only in digital input mode. In case of I2S synchronisation loss, this IRQ is

set to 1.

IRQ2: This IRQ is set to 1 when the device detects any change on the HP Detection pin

(Headphone connection or deconnection).

IRQ3: On the STV82x7, same pins are used for both Headphone and Surround loudspeaker signal

output. A change in the Headphone configuration (HP active or not active) will lead to a signal

switch on those hardware pins. In order to ensure a smooth audio transition, the output is soft muted

before the signal is switched. The IRQ3 is then set to 1 to advise the master processor that the

signal has been switched and to request a HP/Srnd Ouput Un-Mute.

9.3

I²C Bus Expander

Pin BUS_EXP can be used to control external switchable IF SAW filters or audio switches. This pin

can be directly programmed by register RESET.

STV8247T Datasheet(PDF) 44 Page - STMicroelectronics