Technical information

CHAPTER 2

Hardware Design

Sound Expansion Card 31

■ a 16-bit stereo codec

■ a Sound Blaster–compatible mixer with AGC

■ a control interface for the FM synthesizer IC

The CT2501 sound system IC allows analog mixing of audio from the PC and from the

FM synthesizer IC. The audio signal from the sound card is the mixed with the CD audio

from the Macintosh host computer by circuitry on the DOS Compatibility Card. The

resulting sound signal is sent back to the Macintosh computer where it is mixed with the

Macintosh computer’s sound signals and sent to the sound outputs.

YMF262 FM Synthesizer IC 2

The YMF262 IC, a type I3 (OPL3) device, uses FM synthesis to generate sounds. The

YMF262 IC includes the following features:

■ 24 operators conﬁgurable in 4-operator mode for 6 channels

■ 36 operators conﬁgurable in 2-operator mode for either 18 channels or 15 channels

with 5 rhythm channels

■ 8 selectable FM source waveforms

■ 4 channels of sound output

■ hardware vibrato and tremolo effects

■ 2 programmable timers capable of generating interrupt requests

The YMF262 IC interfaces directly to the 8-bit ISA data and address bus; the CT2501 IC

provides the chip select signal.

YAC512 Sound DAC IC 2

The YAC512 IC is a two-channel, 16-bit digital-to-analog converter that interfaces with

the YMF262 FM synthesizer IC to provide analog sound output signals.