10

DS308PP4

CS4281

CrystalClear™ PCI Audio Interface

CIRRUS LOGIC PRODUCT DATA SHEET

is activated when the portable is in the docking station. Software can disable the audio I/O paths on the

portable that are superseded by docking station I/O and enable the paths needed in the docking station.

Note that both interfaces are needed in systems where the CD-ROM analog input is in the portable and the

Line In/Out jacks on the docking stations are used. Using the AC ‘97 digital link across the dock maintains

the absolute highest audio quality along with a standard well-defined non-proprietary interface that will

last through many system generations.

Figure 7 depicts the CS4281 using an AC ‘97 codec in an audio/modem design. The primary AC ‘97 in-

terface is connected to a CS4298 and is used for audio/modem I/O such as Mic In, Line In, Line Out and

the Analog Front End (AFE) for Modem features. The CS4298 analog interface is connected to the DAA

via the EGPIO pins. The EGPIO supports the PCI Power Management Event system wake-up feature al-

lowing a powerdown system to be powered up by an incoming call on the modem.

Host

Memory

North

Bridge

CPU

South

Bridge

CS4297A

PCI Bus

PC/PCI (if used)

Audio Out

Audio In

Figure 5. AC ‘97 Codec Interface

CS4281

Host

Memory

North

Bridge

CPU

South

Bridge

PCI Bus

Audio

Out

Audio

In

Bridge

Audio Out

Audio In

Secondary PCI Bus

PORTABLE

DOCKING STATION

CS4281

Primary

AC-Link

4

5

5

1

Secondary

Serial Data

In

(ASDIN2)

Buffer

5

PCI Audio Interface

PC/PCI

(if used)

CS4297A

CS4297A

Figure 6. Portable Docking Station Scenario