Z89340 datasheet(25/30 Pages) ZILOG

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Z89340

Digital Wavetable Engine

DS96DSP0201

P R E L I M I N A R Y

1-25

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 4-7

These four bits specify depths ranging from plus and mi-

nus a few cents to about two semitones.

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 Accu-

mulator 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.

Oscillator Parameter Block for the Tape Loop

Oscillator

Control Byte

address 0

Filter Q

bits 0-3

Each oscillator has a variable filter. These bits allow ad-

justment of the filter Q. (Refer to Filter Tuning value for

more information.)

Dual Effect Sends

bit 4

When this bit is set, the oscillator talks to two effect chan-

nel, so the effect channel chosen with Effect Channel in

the Effect Send Control Byte, and the subsequent channel

(wraps to effects channel 0 if the last channel is chosen).

This system allows choosing two of the four effects chan-

nels at a time in all but two of the possible combinations.

Half-Speed

bit 5

Half-Speed: Oscillators 0 through 47 (0x2f) can each be

split into two oscillators operating at half the clock rate.

This yields 112 oscillators total (2 . 48 + 16).

Oscillators 48 through 63 (0x30 through 0x3f) can only op-

erate at the full clock rate since the parameter RAM that

would be used as their half-speed counterparts is unavail-

able.

Oscillator-type

bits 6-7

11-extended

opcode

These bits define the operating mode of the oscillator.

Since Tape Loop is an extended opcode, both bits will be

set to 1. For Tape Loop, set the upper four bits of Frequen-

cy Hi to 0000.

Frequency Low

address 1

Envelope-type ATFP

bits 0 and 1

Four types of envelope segments are supported, but only

one at a time. Amplitude/Tremolo/Filter/Pan Envelope-

type control bits.

00-Amplitude

01-Tremolo

10-Filter

11-Pan

Frequency Low

bits 2-7

Always 0 for Tape Loop.

Frequency Mid

address 2

bits 0-7

Always 0 for Tape Loop.

0-f

stereo pan FRONT channels left to right.

20-2f

stereo pan REAR channels left to right.

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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