Z89340 datasheet(28/30 Pages) ZILOG

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Z89340

Digital Wavetable Engine

1-28

P R E L I M I N A R Y

DS96DSP0201

OSCILLATOR PARAMETER BLOCKS (Continued)

Polar Pan Control

address 10

Polar Pan Angle

bits 0-5

There are four main output channels. The spatial location

among them is specified with a modified polar coordi-

nate—a value of 16 is

π/2 radians, 32 is π radians, 48 is

π/2 radians, and so on.

Polar Pan Radius

bits 6-7

The radius select is a two-bit number with 2 at the edge of

the circle and 0 near the center of the circle. A radius of 3

is reserved for stereo panning when only two output chan-

nels are needed. When the radius is 3, the following spe-

cial values of Pan Polar Angle are defined:

Filter Tuning Value

address 11

bits 0-7

This byte specifies what the coefficients of the second-or-

der (two-pole, two-zero) digital filter should be in order to

characterize the response. The filter Q can also be adjust-

ed.

Vibrato Control

address 12

Vibrato Rate

bits 0-3

The four bits of Rate are an unsigned exponential number

that give rates ranging from 0.1 to 10 Hz.

Vibrato Depth

bits 4-6

These three bits specify depths ranging from plus and mi-

nus a few cents to about 1 semitone.

Clear Submix

bit 7

Set this bit when this oscillator should clear the submix

Vibrato Phase

Accumulator

address 13

The vibrato value is derived from a sinewave represented

by the 8-bit Vibrato Phase Accumulator, and is added to or

subtracted from the frequency. The initial vibrato phase

can be set by writing a value to the 8-bit Vibrato Phase Ac-

cumulator—a value of 64 is

π/2 radians, which would start

the vibrato at maximum positive swing. If you want the vi-

brato to swing flat first, initialize the vibrato phase accumu-

lator to 128 corresponding to

π radians, a zero crossing in

the sinewave just before it swings negative.

Delay 1A

address 14

Delay 1B

address 15

Delay 2A

address 16

Delay 2B

address 17

Each oscillator has its own second-order (two-pole, two-

zero) digital filter. At the initialization of an oscillator, these

two delays should be given values of 0 unless a click is

wanted. If desired, the oscillator audio stream can be ex-

amined or modified by accessing the delay registers.

0-f

stereo pan FRONT channels left to right.

20-2f

stereo pan REAR channels left to right.

instead of sending to the output channels, output

is sent to one of 32 submix registers. The submix

Send Control. Submix registers can be selected

as inputs by Tape Loop oscillators (an extended

opcode).

mute the oscillator. The oscillator continues to do

everything else except connect to an output

channel.

sends output to all four output channels equally,

effectively at the center of the circle.

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