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Method for detecting multiple audio/modem codecs

IP.com Disclosure Number: IPCOM000009110D
Publication Date: 2002-Aug-07
Document File: 6 page(s) / 116K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for detecting multiple audio/modem codecs. Benefits include improved functionality.

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Method for detecting multiple audio/modem codecs

Disclosed is a method for detecting multiple audio/modem codecs. Benefits include improved functionality.

Background

              AC '97 codec functions are mapped to the codec register values (see Figure 1).

General description

              The disclosed method is a procedure for pre-operating system software to detect and enumerate multiple audio and modem codecs on a system. The method is comprised of three parts:

·        Detection of the presence of multiple codecs

·        Fast Codec Start algorithm

·        Standard codec detection algorithm

Advantages:

Some implementations of the disclosed structure and method provide one or more of the following advantages:

              The disclosed method provides the capability to detect multiple audio and modem codecs on a PC system.

Detailed description

              The disclosed method detects multiple codecs on a PC system. Several procedures are detailed below, including:

·        Detection of multiple codecs

·        Fast Codec Start algorithm

·        Standard codec detection algorithm

·        Detection of codecs on SDATAIN

Detection of multiple codecs

      The following steps describe how to detect and determine the type of codecs attached to the AC ’97 interface. Use either the CNR plug-and-play (PnP) EEPROM or the hard-coded value for the motherboard codec. The delay to wait for codecs to set the Codec Ready bits is dependant on the Fast Codec Start bit in the EEPROM and the AC’97 version.

1. Check that the CDC_DN_ENABLE# signal is asserted (low).

2. If CDC_DN_ENABLE# is asserted (low):

              a. Check the BIOS to get AC ’97 compliance and fast codec information for the motherboard codec.

              b. If the motherboard codec supports an 800-µs (Fast Codec Start) delay and is AC’97 v2.1 or v2.2 compliant, check the Fast Codec Start bit in the CNR PnP EEPROM to determine the delay; jump to step 2d.

              c. If the motherboard codec does not support an 800-µs (Fast Codec Start) delay and is AC’97 v2.1 or v2.2 compliant, wait the standard delay; jump to step 2h.

              d. Check the CNR PnP EEPROM to get the Fast Codec Start bit for the CNR codec(s) by reading a word from AP+008h (bit 14).

              e. Check the CNR PnP EEPROM to get AC ’97 compliance for CNR codec(s) by reading register 06h-07h.

              f. If the CNR codec(s) support an 800-µs (Fast Codec Start) delay and are AC’97 v2.1 or v2.2 compliant, use the 800-µs delay; jump to step 2h.

              g. If the CNR codec does not support an 800-µs (Fast Codec Start) delay and is AC’97 v2.1 or v2.2 compliant, use the standard delay.

              h. For AC’97 versions later than v2.2, Fast Codec Start may be assumed.

3. If CDC_DN_ENAB# is not asserted (high):

              a. Read the CNR PnP EEPROM to get Fast Codec Start bit for CNR codec to determine the delay (see steps 2d through 2h).

              b. For AC’97 versions later than v2.2, Fast Codec Start may be assumed.

Fast Codec Start algorithm

      The following steps describe a method to detect and determine the type of the AC ’97 codec(s) on the interface (see Figure 2).

1. Enable the audio and modem functions of the AC ’97 digital contro...