CS4281
CrystalClear™ PCI Audio Interface
CPU
North
Bridge
Host
Memory
PCI Bus
South
Bridge
CS4281
CS4297A
Audio Out
Audio In
PC/PCI (if used)
Figure 5. AC ‘97 Codec Interface
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portable that are superseded by docking station I/O and enable the paths needed in the docking station.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.
PORTABLE
CPU
North
Bridge
Host
Memory
DOCKING STATION
PCI Bus
Secondary PCI Bus
CS4281
South
Bridge
PCI Audio Interface
Bridge
Audio Out
CS4297A
Secondary
Serial Data
In
(ASDIN2)
1
5
Buffer
5
Audio In
4
PC/PCI
(if used)
Audio
Out
CS4297A
5
Primary
AC-Link
Audio
In
Figure 6. Portable Docking Station Scenario
CIRRUS LOGIC PRODUCT DATA SHEET
10
DS308PP4
CIRRUS [ CIRRUS LOGIC ]
