CS4281 Datasheet, PDF (9/36 Pages) Cirrus Logic – CrystalClear PCI Audio interface

CS4281
CrystalClear™ PCI Audio Interface
OVERVIEW
The CS4281 provides a low-cost PCI audio solution with Legacy Game compatibility for the PC environ-
ment. The CS4281 is compatible with the CS4614 and CS4280-CM. The CS4281 is divided into several
functional blocks.
• PCI Interface
• Sound System Interface
• FM Synthesis
• Peripheral Devices (MIDI & Gameport)
The PCI Interface is the physical connection to the bus. It is subdivided into several smaller functional
groups such as: PCI configuration and interface, DMA controller, interrupt control, and chip control. The
PCI interface serves as a Master/Target PCI device and its two-base address registers provide access to the
chip operation registers and internal memory blocks. The Sound System Interface provides all the registers
and controls to operate the entire sound system. The FM Synthesis provides full compatibility with market
standard FM-based music synthesis used in DOS games and educational software. The CS4281’s flexibil-
ity is further enhanced by the inclusion of peripheral devices such as Hardware Volume Control, Clock
Generation, General Purpose I/O (GPIO), MIDI UART Port, Game (Joystick) Port, and the AC Link.
The DMA Engine provides dedicated hardware to manage transfer of up to 4 concurrent audio/data streams
to and from host memory buffers. Four Bus Mastering DMA controllers support simultaneous capture,
play, modem transmit, and modem receive.
The CS4281 supports a variety of audio I/O configurations including a single CS4297A CrystalClear
AC ’97 Codec or dual CS4297A codecs where the second codec is used as a portable’s docking station
solution. The combination of a CS4281 with a CS4298 AMC ‘97 codec, provides a cost-effective, superior
quality, two-chip audio/modem solution.
Legacy Support
Legacy games are supported by CrystalClear Legacy Support CCLS™, DDMA, or by the PC/PCI inter-
face. In both motherboard and add-in card designs, CCLS and DDMA provide support for legacy games
by providing a hardware interface that supports a Sound Blaster Pro™ compatible interface, as well as sup-
port for FM, and joystick interfaces. These hardware interfaces provide PCI-only games compatibility for
real-mode DOS and Windows DOS box support.
For motherboard designs, PC/PCI is used by connecting the PCGNT# and PCREQ# pins to the appropriate
pins on the south bridge motherboard chip. The PC/PCI interface is compliant with Intel’s PC/PCI spec.
(version 1.2).
SYSTEM ARCHITECTURES
A typical system diagram depicting connection of the CS4281 to the CrystalClear CS4297A AC ’97 Codec
is given in Figure 5. All analog audio inputs and outputs are connected to the CS4297A. Audio data is
passed between the CS4297A and the CS4281 over the serial AC-Link. The CS4281 provides a hardware
interface for connection of a joystick and MIDI devices.
Figure 6 depicts the CS4281 using both AC ‘97 codec interfaces in a portable design. The primary AC ‘97
interface is connected to a CS4297A used for all audio I/O inside and connected to the portable. The second
AC ‘97 interface is sent across to the docking station which contains a second CS4297A. The second codec
CIRRUS LOGIC PRODUCT DATA SHEET
DS308PP4
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