CS42435 datasheet(32/58 Pages) CIRRUS

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DS685F1

CS42435

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.

5.4.1

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 3 for the required frequen-

cy range.

5.4.2

Software Mode

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

(MFREQ[2:0])” on page 42.

5.5

CODEC Digital Interface

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

bit depths from 16 to 32 as shown in Figure 13 on page 33. 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

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 3. MCLK Frequency Settings

Gain

-10dB

0dB

Frequency

T2 = 15 µs

T1=50 µs

3.183kHz

10.61kHz

Figure 12. De-Emphasis Curve

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