4.5.1. Hardware interface

The baseboard provides a National Semiconductor LM4549 audio CODEC. The audio CODEC is compatible with AC’97 Rev 2.1 and features sample rate conversion and 3D sound. The CODEC is driven with a PrimeCell AACI (PL041) instantiated into the core module FPGA.

Figure 4.9 shows the architecture of audio interface. (Line out is the top connector.)

Figure 4.9. Audio interface

The CODEC is provided with a microphone input that can be configured by a link to support either passive or dynamic (electret) microphones:

The default configuration supports a passive microphone. Only monophonic sound is supported, but microphone channel MIC1 or MIC2 can be selected in software.

The line output is provided with a 0.25W RMS unity-gain amplifier and enables you to connect 32Ω (or higher) headphones or speakers directly to J10.

The signals associated with the audio CODEC interface are assigned to the HDRB socket pins as shown in Table 4.10.

Table 4.10. Audio CODEC signal assignment

Signal nameHDRB Description
AACI_SDATA_OUTF7Serial data from AACI to the CODEC
AACI_BIT_CLKF6Clock from the CODEC
AAC_SYNCF8Frame synchronization signal from the AACI
AACI_SDATA_INF5Serial data from the CODEC to the AACI
AACI_RESETF13Reset signal from the PrimeCell AACI


For a description of the audio CODEC signals, refer to the LM4549 datasheet available from National Semiconductors.

Copyright © 2002 ARM Limited. All rights reserved.ARM DUI 0159B