CS42436 datasheet(34/66 Pages) CIRRUS

34 / 66 page

DS647PP2

De-emphasis is only available in Single Speed Mode. Please see “DAC De-Emphasis Control

(DAC_DEM)” on page 46 for de-emphasis control.

5.4

System Clocking

The CODEC serial audio interface ports operate as a slave and accept externally generated clocks.

The CODEC requires external generation of the master clock (MCLK). The frequency of this clock must

be an integer multiple of, and synchronous with, the system sample rate, Fs.

Hardware Mode

The allowable ratios include 256Fs and 512Fs in Single-Speed Mode and 256Fs in Double-Speed Mode.

The frequency of MCLK must be specified using the MFREQ (pin 3). See Table 5 below for the required

frequency range.

Software Mode

The frequency range of MCLK must be specified using the MFREQ bits in register “MCLK Frequency

(MFreq[2:0])” on page 45.

5.5

CODEC Digital Interface

The ADC and DAC serial ports operate as a slave and support the TDM digital interface formats with vary-

ing bit depths from 16 to 32 as shown in Figure 14. Data is clocked out of the ADC on the falling edge of

SCLK and clocked into the DAC on the rising edge.

TDM is the only interface supported in hardware and software mode.

5.5.1 TDM

Data is received most significant bit (MSB) first, on the second rising edge of the SCLK occurring

after an FS rising edge. All data is valid on the rising edge of SCLK. The AIN1 MSB is transmitted

early but is guaranteed valid for a specified time after SCLK rises. All other bits are transmitted

on the falling edge of SCLK. Each time slot is 32 bits wide, with the valid data sample left justified

within the time slot. Valid data lengths are 16, 18, 20, or 24.

SCLK must operate at 256Fs. FS identifies the start of a new frame and is equal to the sample

rate, Fs.

Ratio (xFs)

MFREQ

Description

SSM

DSM

QSM

1.5360 MHz to 12.8000 MHz

256

N/A

2.0480 MHz to 25.6000 MHz

512

256

N/A

Table 5. MCLK Frequency Settings

Gain

-10dB

0dB

Frequency

T2 = 15 µs

T1=50 µs

3.183 kHz

10.61 kHz

Figure 13. De-Emphasis Curve

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