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Musical-Applications-of-Microprocessors-2ed-Chamberlin-H-1987

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336 MUSICAL ApPLICATIONS OF MICROPROCESSORS<br />

TEMPO<br />

CONTROL<br />

t THEME INTERVAL<br />

W X Y Z ABC D<br />

ILOW-FREOUENCYI<br />

OSC<br />

OF<br />

lOGIC<br />

ONE '*<br />

ON<br />

-0-32<br />

COUNT<br />

01 C- 1/2<br />

02 CI<br />

04 C2<br />

...... CLK<br />

08 C4<br />

016 C8<br />

Lr ~,<br />

COUNT<br />

ClK<br />

Lrto,,,<br />

0<br />

ClK<br />

,I J<br />

C3<br />

C6<br />

-DATA<br />

IN 01 81<br />

02 82<br />

31<br />

STAGE 03 83<br />

SHIFT<br />

REG.<br />

04 84<br />

027 827<br />

028 828<br />

029 829<br />

030 83o<br />

-ClK 031 83 I<br />

lS8<br />

MS8<br />

I GENERATOR<br />

PARITY IMAJOR SCALE<br />

I I I<br />

TRANSLATION<br />

lOGIC<br />

•••••<br />

5 81T DAC<br />

I<br />

PITCH CONTROl~<br />

Fig. 10-11. Block diagram <strong>of</strong> Muse<br />

·<br />

[3-aJ<br />

connected to 40 signal rows. Eight 40-position slide switches divided into<br />

two groups <strong>of</strong> four switches act as columns and can select any individual row<br />

signal. Four <strong>of</strong> the switches, which are called "theme" controls, feed a parity<br />

generator whose output feeds the 31-position shift register. The other four<br />

switches, designated "interval" controls, are connected through some translation<br />

logic to a 5-bit DAC, which drives a VCO tone generator and output<br />

speaker. The VCO and DAC are adjusted so that the step size is a semitone<br />

on the equally tempered scale and the translation logic converts its 4-bit

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