WM8850 datasheet(32/223 Pages) WOLFSON

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WM8850

Pre-Production

PP, April 2011, Rev 3.2

Loss of Lock

Should the S/PDIF Rx lose lock, an unsolicited response will be triggered to indicate the change in

lock status. The data in the link sample blocks will be set to 0, and the stream will continue to run at

the previously recovered sample rate. There may be several samples of data before the unsolicited

response can be sent, but the data will be zeroed immediately.

If the S/PDIF Rx is in Software Formatted S/PDIF mode, and the loss of lock event occurs, all 32-bits

of the data are zeroed.

Change in Sample Rate

Once a stream has started, stream parameters such as sample-size, number of channels, and

sample rates should not be changed. For the S/PDIF Rx audio path, it is expected that any change of

S/PDIF sample rate will cause the S/PDIF Rx to lose lock.

Once the S/PDIF Rx has gained lock to the new sample rate (or regained lock at the existing sample

rate), the controller will be sent an unsolicited response.

The S/PDIF Rx audio path has two methods of handling the relock condition:

Push Method: where upon lock, the stream (assuming SRC1 is bypassed) immediately

changes sample rate to the new recovered rate, and data is no longer overwritten with

zeros.

Controlled Method: where zeroed data continues to be transmitted at the old sample rate,

until the stream ID is set to 0. Upon re-assignment of the Stream ID, non-zeroed stream

data is transmitted at the newly recovered sample rate.

These methods are selected using the Unlock Ctrl register in the SPDIF_IN Control Verb.

S/PDIF TX VALIDITY FLAG

The validity flag is bit [28] of an S/PDIF sub-frame. It is configured using V-bit in the Digital Converter

Control Verb.

When the V-bit is set to 1, the validity flag for both sub-frames is set to 1.

When the V-bit is set to 0, the validity flag for both sub-frames is set to 0, unless an invalid sample is

being transmitted for that sub-frame - in which case the validity flag is set to 1 for that sub-frame.

An invalid sample may occur under the following conditions:



The Stream ID is set to 0



SRC2 is enabled but is unlocked



There has been a FIFO overrun/under-run condition in the S/PDIF Tx Stream Manager (i.e.

a Stream Error).

Note: A Stream Error problem would only be present due to a problem upstream of the WM8850. A

Stream Error triggers an unsolicited response with the EF_STREAM_ERR flag set. If an invalid

sample is detected, it will be overwritten with all-zeros if VCFG in the Digital Converter Control Verb is

set to 1.

CHANNEL NUMBERING

Multi-Channel Streams

Channels 0, 2, 4, etc will be assigned to the Left Channel of a stereo converter. Channels 1, 3, 5, etc

will be assigned to the Right Channel of a stereo converter.

Channel synchronisation between channels is only guaranteed where stream packets are received by

the WM8850 after all converters in a multi-channel stream have had their stream ID assigned.

WM8850 Datasheet(PDF) 32 Page - Wolfson Microelectronics plc

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