SAA7780 Ver la hoja de datos (PDF) - Philips Electronics
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SAA7780 Datasheet PDF : 70 Pages
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Philips Semiconductors
Product Specification
ThunderBird Q3D PCI Audio
Accelerator
SAA7780
Pro mixer registers. These registers are used as a mailbox to the DSP data bus to deliver data to the SoundBlaster
Emulation code. The SAA7780 chip supports DMA to the Sound Blaster that legacy code requires. All data transmitted
over the SoundBlaster Registers is processed by the DSP to emulate the Sound Blaster Pro hardware.
OPL3 Registers and the FM Accelerator
The OPL3 register interface is a subset of the complete SoundBlaster register set. The OPL3 registers are separate to
point out that the FM legacy is supported at the register level. The OPL3 registers simply pass FM synthesis commands
to the SoundBlaster Emulation code and receive status from the same code.
Virtual Registers
The Virtual Registers interfaces the PCI bus and two substantial wavetable synthesis accelerators: the Sample Fetch
and Address Generation accelerators. The Virtual Registers is responsible for setting up the PCI interface for master
cycles data fetches and retrieving those fetches into a sample buffer. The Virtual Registers get commands from the
Address Generation accelerator and turns them into PCI master requests. Once the data has been retrieved, the Virtual
Register then instructs the Sample Fetch accelerator to process a block of data. Once the processing is complete, the
Sample Fetch Accelerator notifies the Virtual Registers that all is clear and that new data can be processed.
Address Generation Accelerator
The Address Generation accelerator is a preprocessing unit for the sample fetching mechanism inside the Virtual
Registers. The Address Generator will get a set of parameters from the DSP code on a per voice basis for either
DirectSound processing or wavetable synthesis. Once these voice parameters are set, the hardware is instructed to
translate the addresses and fetch the audio samples from system memory. The Address Generator is also capable of
looping with intervention from the DSP code. The DSP kills voices by instructing the Address Generator to stop fetching
data. Once the samples are fetched, they are stored in the Virtual Register’s input sample buffer for processing by the
Sample Fetch Accelerator.
Sample Fetch Accelerator
The Sample Fetch accelerator is used to process audio samples fetched by the Virtual Registers and deliver them to
the DSP code for further processing. This processing can include pitch shifting or rate conversion. The degree of pitch
shifting is under direction of DSP code indicating the Sample Fetch accelerator is programmable. The input samples
are taken from the Virtual Register’s input sample buffer and stored in DSP memory space.
MIDI Registers and UART
An MPU401 compatible UART is supplied to enable external MIDI devices to use the SAA7780 chip synthesizers as
well as its external device’s own synthesizer. The MIDI register interface is used to pass the MIDI command stream
from the host to the DSP firmware for parsing into synthesizer commands. The MPU401 UART always operates in
“dumb”mode. Both the PCI and DSP can access the MIDI UART directly. Data is presented from/to the MPU401
Registers in a mailbox fashion to the MPU401 UART.
Music DAC Interface
The music DAC interface allows for an inexpensive, high quality, playback of the final stereo mix or for providing the
unique QUAD feature when used in conjunction with the standard AC97 V1.03 CODEC. The interface is a standard
EIAJ format supporting many brands of inexpensive 16 bit DACs. The Music DAC interface is capable of playback
sample rates from 22.05 - 48.0 KHz.
1999 Sep 30
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