LM4560 datasheet(32/54 Pages) NSC

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4.0 Functional Description (Continued)

4.1 WAVE ENGINE

Feature:

•

64 voice synthesis

•

Each voice channel typically consumes 0.25% PCI band-

width

•

8/16 bits, mono/stereo, unsigned/signed samples at arbi-

trary sample rate

•

Unlimited length of wave samples

•

Internal 26 bits computation, DAC driven up to 20 bits

•

Double buffering envelope curve

•

Pitch shifting

•

0–6 Hz low frequency oscillator

•

FM/AM modulation

•

Chorus, Reverb effect

•

Recording/Playback full-duplex

•

Main Mixer capture

•

Microphone channel capture

•

2S interface

•

S/PDIF interface

•

Modem data rate conversion

4.1.1 Scheduler

Wave engine process SRC (Sample Rate Conversion), EM (Envelope Modulation), FM (Frequency Modulation), AM (Amplitude

Modulation) and DM (Digital Mixing) channel by channel. A central controller called

Scheduler will decide the processing se-

quence of up to 64 playback channels (including up to 10 special channels) and 1 legacy playback/recording channel.

To optimize PCI bus utilization, Scheduler decides each channel’s priority according to the following rules:

•

Legacy playback/recording channel always has the high-

est priority.

•

Channels which require PCI bus cycle, i.e. cache miss

channels, have higher priority.

DS100910-4

FIGURE 3. Testing Specification Standard

LM4560 数据表(PDF) 32 Page - National Semiconductor (TI)

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