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Production Data

WM1811A

PD, November 2013, Rev 4.1

The following description of the DRC is applicable to both DRCs. The associated register control fields

are described inTable 27 and Table 28 for the respective DRCs.

Note that, wherethe following description refers to register names, the generic prefix [DRC] is quoted:



For the DRC associated with AIF1, [DRC] = AIF1DRC1.



For the DRC associated with AIF2, [DRC] = AIF2DRC.

DRC COMPRESSION / EXPANSION /LIMITING

The DRC supports two different compression regions, separated by a “Knee” at a specific input

amplitude. In the region above the knee, the compression slope [DRC]_HI_COMP applies; in the

region below the knee, the compression slope [DRC]_LO_COMP applies.

The DRC also supports a noise gate region, where low-level input signals are heavily attenuated. This

function can be enabled or disabled according to the application requirements. The DRC response in

this region is defined by the expansion slope [DRC]_NG_EXP.

For additional attenuation of signals in the noise gate region, an additional “knee” can be defined

(shown as “Knee2” in Figure 21). When this knee is enabled, this introduces an infinitely steep drop-

off in the DRC response pattern between the [DRC]_LO_COMP and [DRC]_NG_EXP regions.

The overall DRC compression characteristic in “steady state” (i.e. where the input amplitude is near-

constant) is illustrated in Figure 21.

Figure 21 DRC Response Characteristic

The slope of the DRC response is determined by register fields [DRC]_HI_COMP and

[DRC]_LO_COMP. A slope of 1 indicates constant gain in this region. A slope less than 1 represents

compression (i.e. a change in input amplitude produces only a smaller change in output amplitude). A

slope of 0 indicates that the target output amplitude is the same across a range of input amplitudes;

this is infinite compression.

When the noise gate is enabled, the DRC response in this region is determined by the

[DRC]_NG_EXP register. A slope of 1 indicates constant gain in this region. A slope greater than 1

represents expansion (ie. a change in input amplitude produces a larger change in output amplitude).

When the DRC_KNEE2_OP knee is enabled (“Knee2” in Figure 21), this introduces the vertical line in

the response pattern illustrated, resulting in infinitely steep attenuation at this point in the response.

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