Single-Chip PC Sound System

AD1812 SoundPort® controller integrates DSP and codec, supports PC standards, simplifies motherboard

The AD1812*SoundPort Controller is a single-chip audio sub-system for adding 16-bit stereo audio to personal computers. The ISA Plug and Play (PnP) system is compatible with applications written for Windows 95, the Microsoft Windows® Sound System, Sound Blaster Pro® and Ad Lib®, and provides an MPU-compatible interface and a game port complete with timer.

ISA PnP Interface:

The chip is complete with all necessary PnP bus interface logic. This includes address decoding for on-board resources, control and signal interpretation, DMA selection and control logic, IRQ selection and control logic, all interface configuration logic. The AD1812 can support two, or three DMA channels. Included are dual DMA count registers for full-duplex operation, enabling simultaneous capture and playback on separate DMA channels. The AD1812 is configurable according to the Plug and Play ISA Specification. Table 1 lists the logical devices supported by the AD1812 that ROM coded in its PnP space. For a non-Plug and Play environment, the built in PnP services allow theAD1812 to operate under a user-defined fixed address space.

Table 1. Emulated Logical Devices

Logical Device Number Emulated Device
0 Windows Sound System
1 Sound Blaster Pro v.2.01
2 OPL3 Music Synthesizer
3 MIDI MPU-401 port
4 Game/Joystick port
5 Modem

Codec:

The built-in 16-bit SoundPort® Stereo Codec supports business audio and multimedia applications. The codec includes stereo audio converters, complete on-chip filtering, an MPC Level-2- compliant analog mixer, and FIFOs for buffering the ISA The pair of 16-bit outputs from the ADCs are available over a bit bidirectional interface that also supplies 16-bit digital data

Figure 1
Figure 1. AD1812 block diagram.

to the DACs. The codec can accept and generate 16-bit twos-complement PCM linear (big-endian or little-endian) digital data, 4-bit IMA-ADPCM compatible digital data, 8-bit unsigned magnitude PCM linear data, and 8-bit m-law or A-law companded digital data..

Multimedia Support:

The SoundPort Controller combines an embedded 16-bit fixed-point Analog Devices signal processor and dedicated hardware to emulate all Sound Blaster version 2.01 functions. The ROM-coded music synthesis algorithms imitate industry-standard OPL3 FM synthesizer chips and can deliver 20 voice polyphony.

MPU-401:

The primary interface for communicating MIDI data to and from the host PC is the emulated MPU-401 interface, which includes a built-in FIFO for communicating to the host bus.

Game Port:

The chip includes an IBM-compatible game port interface, capable of supporting up to two joysticks. Connecting the game port to a 15-pin D-sub connector requires only a few capacitors and resistors.

Systems Are EasyTo Build:

The AD1812 has everything needed for a PnP audio controller and in a form more integrated than one might expect. The internal PnP services can decode up to 6 logical devices for designing seamlessly integrated subsystems. No known audio controller offers as much!

Figure 2
Figure 2. Audio/telecom PnP ISA system

Functioning as more than just a codec, the AD1812 enables multimedia and telephony in any PC. When coupled with a modem chip set, the subsystem can provide 16-bit sound support for popular DOS games andWindows 95 audio applications, fax, full-duplex speaker phone, and a high-speed modem. For even more realistic music, aWavetable synthesizer's output can be mixed with the Wave audio converted by the on board DACs.

As an aid to the designer,Analog Devices offers reference designs for the AD1812 & modem chip set, and the AD1812 & Wave Blaster header. Device drivers are available for Windows 95, Windows 3.1x, Windows NT, and OS/2.

Availability:

The AD1812 is available for 0 to +70°C in 160-pin plastic quad flat pack (PQFP) and thin quad flat pack (TQFP) packages.

The AD1812 analog design team was led by Bob Libert, at Wilmington MA; the digital design team was led by John Amann, and the software team by Chris Russell, at Norwood MA.

Об авторах

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David Babicz