WM8962B datasheet(95/295 Pages) WOLFSON

95 / 295 page

WM8962

Rev 4.3

T-LOOPBACK

The T-Loopback function provides a specialised mode for use in communications applications such as

VOIP handset configurations. The T-Loopback configuration provides a mono ADC and mono DAC

signal to be output via the Digital Audio Interface transmit path. This allows Acoustic Echo

Cancellation to be performed using difference algorithms implemented on an external processor.

T-Loopback is enabled by setting the TLB_ENA register bit, as described in Table 51.

When T-Loopback is enabled, the Digital Audio Interface outputs are configured according to the

TLB_MODE bit, as described below.

DESCRIPTION

LEFT AIF OUTPUT

RIGHT AIF OUTPUT

TLB_MODE = 0

Left ADC

(Left DAC + Right DAC)/2

TLB_MODE = 1

(Left DAC + Right DAC)/2

Right ADC

Table 50 T-Loopback Mode Select

Note that the Left ADC and Right ADC signals can be digitally mixed, if required. This enables the

sum of the Left and Right ADC channels to be output in T-Loopback. The ADC Monomix feature is

described in the “ADC Monomix” section.

Note that the Left DAC and Right DAC signals used in the T-Loopback are also controlled by the DAC

Digital Volume controls (see “Digital-to-Analogue Converter (DAC)”). It is possible to output just a

single DAC channel in T-Loopback mode by setting the Digital Volume to zero in the unwanted

channel.

The register bits associated with T-Loopback are described in Table 51.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R285 (011Dh)

Tloopback

TLB_ENA

T-Loopback Enable

0 = Disabled

1 = Enabled

TLB_MODE

T-Loopback Mode Select

0: Left AIF Output = Left ADC; Right AIF

Output = (Left DAC + Right DAC) / 2

1: Left AIF Output = (Left DAC + Right

DAC) / 2; Right AIF Output = Right ADC

Table 51 T-Loopback Control

The signal paths when T-Loopback is enabled (TLB_ENA = 1) are illustrated in Figure 30.

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