CS5378 datasheet(24/86 Pages) CIRRUS

24 / 86 page

CS5378

DS639F1

7. SYNCHRONIZATION

The CS5378 has a dedicated SYNC input that

aligns the internal digital filter phase and generates

an external signal for synchronizing modulator an-

alog sampling. By providing simultaneous rising

edges to the SYNC pins of multiple CS5378 devic-

es, synchronous sampling across a network can be

guaranteed.

7.1 Pin Description

SYNC - Pin 19

Synchronization input, rising edge triggered.

7.2 MSYNC Generation

The SYNC signal rising edge is used to generate a

retimed synchronization signal, MSYNC. The

MSYNC signal reinitializes internal digital filter

phase and is driven onto the MSYNC output pin to

phase align modulator analog sampling.

The MSEN bit in the digital filter CONFIG register

(0x00) enables MSYNC generation. See “Modula-

tor Interface” on page 36 for more information

about MSYNC.

7.3 Digital Filter Synchronization

The internal MSYNC signal resets the digital filter

state machine to establish a known digital filter

phase. Filter convolutions restart, and the next out-

put word is available one full sample period later.

Repetitive synchronization is supported when

SYNC events occur at exactly the selected output

rate. In this case, re-synchronization will occur at

the start of a convolution cycle when the digital fil-

ter state machine is already reset.

7.4

Modulator Synchronization

The external MSYNC signal phase aligns modula-

tor analog sampling when connected to the CS5371

MSYNC input. This ensures synchronous analog

sampling relative to MCLK.

Repetitive synchronization of the modulators is

supported when SYNC events occur at exactly the

selected output rate. In this case, re-synchroniza-

tion always occurs at the start of analog sampling.

7.5 Test Bit Stream Synchronization

When the test bit stream generator is enabled, an

MSYNC signal can reset the internal data pointer.

This restarts the test bit stream from the first data

point to establish a known output signal phase.

The TSYNC bit in the digital filter TBSCFG regis-

ter (0x2A) enables synchronization of the test bit

stream by MSYNC. When TSYNC is disabled, the

test bit stream phase is not affected by MSYNC.

Figure 13. Synchronization Block Diagram

SYNC

MSYNC

Digital

Filter

Generator

MSYNC

MSEN

TSYNC

Test Bit

Stream

Output

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