SAA7780 Просмотр технического описания (PDF) - Philips Electronics
Номер в каталоге
Компоненты Описание
производитель
SAA7780 Datasheet PDF : 70 Pages
| |||
Philips Semiconductors
Product Specification
ThunderBird Q3D PCI Audio
Accelerator
SAA7780
Clocks and the PLL Subsystem
Clocks for operation of the SAA7780 are derived from two sources; an external crystal and bit clock from the AC97
CODEC. The SAA7780 PLL Subsystem derives its reference from the external crystal.
FIGURE 4
15pF
14.318MHz
xtalin
SAA7780
15pF
xtalout
The SAA7780 substem consists of a fixed layout PLL cell and a digital interface to the 8 bit PS bus. The PLL is
designed to drive the clocks for the DSP subsystem. The implementation calls for the PLL to be utilized with complete
programmable register interface to enable the tuning of the frequencies as necessary.
Multimedia Timer
The SAA7780 chip supplies a 20-bit, 1uS resolution timer for game synchronization. The timer data can be accessed as
an I/O device. This timer can be used by game developers to keep track of time elapsed to synchronize the video to the
audio stream. The timer can be polled or interrupt driven and is selectable by the user application.
DMA is for the Sound Blaster registers, the DSP Mastering Device (DMD), and the Audio codec. To cover as many
systems as possible, the DMA interface supports three modes for legacy support: Mobile PC/PCI DMA Arbitration
(PC/PCI), Distributed DMA (DDMA), and Legacy Accommodation Mode (LAM).
Legacy Accommodation Mode allows the SAA7780, in an architecturally compatible system, to snoop and snarf
selected DMA cycles on the PCI bus that were intended to the ISA Bridge. If a chip set supports Distributed DMA, the
SAA7780 will use this method since it is more efficient than LAM. Additionally, PC/PCI can be utilized as well if neither
DDMA nor LAM are supported on the selected chip set.
AC Link and the DSP Master Device Interface
The SAA7780 chip provides support for the AC97 specification by supplying an AC Link interface to communicate with
an industry standard AC97 CODEC. The AC Link interface is set up to allow the PCI, DMA and DSP busses to interface
with the AC97 codec via the AC Link. The AC Link is compliant with the release 1.03 of the AC97 specification.
Sound Blaster Registers
The other device that requires DMA is the SoundBlaster registers. DMA is used to transfer SoundBlaster digital audio
files from the host to a codec for playback in addition to providing a mailbox for other commands. In order for the DSP
to emulate the Sound Blaster sound effects, a legacy register set must be implemented to capture these commands.
These sixteen, 16-bit registers are used primarily to emulate SoundBlaster Pro register set as well as the SoundBlaster
1999 Sep 30
12
Share Link: 