SN66020B

4-Channel Speech Controller

5.5. Sampling Rate Counters

4 independent sampling rate counters are dedicated to 4 individual voice channels to

play voices with different playing rates. The playing rate is programmable from 4KHz

to 40KHz. The resolution of sampling period of each sampling rate counter is 0.25 uS.

This feature helps SN66020B play sounds with accurate pitches in the case of music

instrument synthesis.

5.6. Auto repetition

Auto repetition function helps SN66020B realize a “looping” sound automatically by

hardware without any software effort.

Auto repetition function is a very useful

mechanism to implement “Sustain” sound in instrument synthesis. All 4 channels are

equipped with this function. Arbitrary lengths of looping sound are accepted by

SN66020B.

5.7. I/O Ports

P1 is a 4-bit input port, P2/P3 are two 4-bit I/O ports and P4 is a 4-bit output port. Any

bit of P2 and P3 can be programmed to be input or output individually. Any valid data

transition (H

L or L H) of P1, P2 and P3 can reactivate the chip when it is in

power-down stage.

To Internal Data Bus

Read Control

PAD

Weak

Input Port Configuration (P10~P13)

Ver: 1.1

December 6, 2004

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