WM8850
Pre-Production
INTRODUCTION
The WM8850 is a high performance multi-channel audio CODEC designed for high performance PC
audio systems. The device offers full compatibility with the Intel High Definition Audio (HDA)
specification revision 1.0, allowing seamless integration with industry-standard HDA controllers.
The WM8850 has three high performance stereo DACs to enable six channels of high definition
audio, ideal for 5.1 channel applications. A high-performance ground-referenced stereo headphone
amplifier utilises advanced charge pump and DC servo technology to minimise system cost and
space without compromise on audio quality. Two stereo pairs of line outputs are also provided.
These line outputs may be used at the output of the PC to enable connection to a 5.1 speaker
system, or may be used connected to external speaker drivers in a notebook or netbook application.
The WM8850 also has two high performance stereo ADCs to provide Hi-Fi quality analogue line-in
and microphone input digitisation. A low noise microphone bias with programmable output voltage is
provided, ideally suited as a bias current source for ECM microphones. Additionally, the CODEC
contains a digital microphone interface capable of supporting up to four independent digital
microphones, allowing high quality microphone array implementations to be realised. One differential
stereo input is provided for line level signals, while one pseudo-differential stereo input with integrated
microphone preamplifier is provided.
The WM8850 also contains a S/PDIF transceiver which is fully compatible with IEC-60958-3. The
S/PDIF receive and transmit paths each contain a sample rate converter (SRC) to enable
asynchronous sample rate conversion between the S/PDIF receive/transmit and HDA interface clock
domains. An additional S/PDIF transmitter is provided to allow direct output of a stereo stream from
the HDA interface.
The WM8850 includes an integrated beep generator allowing system beeps to be played back
through the output paths.
This datasheet assumes familiarity with the High Definition Audio Specification Revision 1.0, available
from http://www.intel.com/standards/hdaudio/. For those verbs implemented in the WM8850 which
are as defined in the High Definition Audio Specification Revision 1.0 there is no detailed text
describing their use in this datasheet. However, detailed text describing the function of of vendor-
specific verbs is provided. Additionally, a full list of each node and each verb implemented in the
WM8850 is provided at the rear of the document.
WOLFSON INTERPRETATION OF HDA SPECIFICATION
DOLBY AC3 (IEC-61937)
The AFG node and Converter Widget nodes have a parameter called AC3 within the Supported
Stream Formats Parameter. The Intel High Definition Audio specification states that AC3 should be
set to 1 if the node supports Dolby AC3 (IEC-61937) encoded data.
There is some ambiguity as to what is meant by “supports Dolby AC3 (IEC-61937)”. The WM8850
does not support processing of Dolby AC3 (IEC-61937) encoded data but it does support the passing
of AC3 data through the S/PDIF Converter Widgets.
Wolfson interpret the Intel specification to mean that the AC3 parameter should be set if a node
supports the encoding/decoding of AC3 data, and so we set the WM8850 AC3 parameters to 0.
When the S/PDIF Converters are passing AC3 (IEC-61937) data, the Stream Format Verb for the
widget node should have Bits = 1 (for 16-bit formatting) and Type = 1 to indicate that non-PCM data is
being passed. Note that setting Type is for controller purposes only, and the WM8850 performs the
same operation regardless of what Type is set to.
The user should ensure that Sample Rate Converters (SRCs) are bypassed when S/PDIF contains
AC3 data.
FLOAT32
The WM8850 performs a Fixed-point/Floating-point conversion. Fixed point format is <1,23>, while
floating point format is IEEE-754, single precision 32-bit, full scale between -1.0 and 1.0 with silence
at 0.0.
PP, April 2011, Rev 3.2
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
