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Audio Controller Auto Detect Method Based on Clock Toggling

IP.com Disclosure Number: IPCOM000019846D
Publication Date: 2003-Oct-01
Document File: 2 page(s) / 275K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method that uses the difference in link signal characteristics between viz BITCLK and v/s BITCLK to determine the correct mode of operation. Benefits include using the same controller with different board designs.

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Audio Controller Auto Detect Method Based on Clock Toggling

Disclosed is a method that uses the difference in link signal characteristics between viz BITCLK and v/s BITCLK to determine the correct mode of operation. Benefits include using the same controller with different board designs.

Background

Azalia is a new audio controller, which also contains the older audio controller called AC97. Both of these audio controllers use the same buffer set; however, link protocol and operation between these two standards are not compatible. Since only controller can be active at a time, BIOS is required to determine the mode of operation, which is either viz AC97 or Azalia-based on the codecs attached to the link.

The link clock called BITCLK is an input in AC97 Mode and an output is Azalia Mode. This BITCLK is used to determine whether AC97 or Azalia codecs are present in the system. This is used by the System BIOS to correctly program the Audio sub-system.

General Description

In the disclosed method, the auto-detect logic relies on system BIOS to follow a simple procedure: to check whether the AC97-primary codec is present. This scheme makes no assumptions regarding the exact timing of the AC97 codec or when the clock begins to run in a stable manner. It instead expects BIOS to use the following procedure:

 

  • Enable the detection logic (via CkDetectEnCfg configuration bit)
  • Disable the detection logic (via CkDetectEnCfg configuration bit)
  • Read AZ_AC97# status bit (read-only)
  • Write a valu...