WM9082

Production Data

w

PD, August 2012, Rev 4.1

10

The channel selection for the WM9082 speaker driver is implemented automatically by sensing which

of the inputs pins is CLK and which pin is DATA, as defined in Table 1.

To ensure correct channel selection, it must be ensured that the DATA input is disabled whenever the

CLK input is disabled. If the DATA input signal is present when CLK is disabled, this may result in

incorrect channel selection.

INPUT CONFIGURATION

SPEAKER CHANNEL

CLK = IN1

DATA = IN2

Left

CLK = IN2

DATA = IN1

Right

Table 1 PDM Channel Selection

If stereo operation is required, using two WM9082 speaker drivers, then this can be implemented very

easily, by cross-connecting the CLK and DATA wires on the two speaker drivers, as illustrated in

Figure 2.

Figure 2 Stereo PDM Operation

The channel detection is determined automatically at device start-up, and also after any period when

the CLK input has stopped.

DEVICE CONTROL CODES

When power supplies are present (see “Recommended Operating Conditions”), and audio data is

input at the audio interface, the WM9082 powers up and the Class D speaker driver is enabled. The

WM9082 selects either the Left or Right channel data as described in “PDM Audio Interface”.

The WM9082 can be controlled using specific data sequences, known as Control Codes, received

over the PDM audio interface. Each Control Code is a “zero” code when decoded as audio data.

Therefore, the Control Codes can be transmitted to the WM9082 in the form of silent audio data, but

the codes will be recognised by the WM9082 as control instructions.

The WM9082 Control Codes are defined in Table 2 and Table 3.

The Control Codes are 8-bit codes, which must be transmitted LSB first.

The Page 1 Control Codes (see Table 2) are valid when transmitted consecutively for the required

number of times. The Page 2 Control Codes (see Table 3) are valid only when preceded by the “Page

2 access” instruction (ie. Page 1, Code 6).

In most cases, the Control Codes are only valid if they are received more than 32 times consecutively

(see below for further details). For greatest reliability, however, it is recommended that the host device

always transmits Control Codes at least 64 times whenever it is desired to send a control instruction

to the WM9082.

If the WM9082 is configured to receive Left channel data, then it will only respond to Control Codes

received on the Left channel of the PDM interface. Similarly, if the WM9082 is configured to receive

Right channel data, then it will only respond to Control Codes received on the Right channel.