Z89340 datasheet(26/30 Pages) ZILOG

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Z89340

Digital Wavetable Engine

1-26

P R E L I M I N A R Y

DS96DSP0201

OSCILLATOR PARAMETER BLOCKS (Continued)

Frequency Hi

address 3

Frequency Hi

bits 0-3

These are:

Extended Opcode

bits 4-7

With the Tape Loop Oscillator, the upper four bits of Fre-

quency Hi are one of the extended opcodes and must be

0000.

Phase

address 4

Regeneration

bits 0-7

This value controls the amount of delayed signal that gets

mixed back into the input of the delay line.

Wave Pointer Hi

address 5

ROM16-ROM23

bits 0-7

The eight bits of Wave Pointer Hi control wave ROM or

RAM address lines 16-23, which are the highest address

bits. This value remains fixed throughout the life of a note.

The lower bits of Wave Pointer are changed by the Z89340

during the life of a sound until they equal Wave Endpoint.

ROM23/DMA

bit 7

If DMA bus-mastering mode is enabled, this bit enables

DMA for the oscillator. The address then becomes an ISA

Bus host CPU RAM address. DMA has system conse-

quences and should be used with caution. In particular,

fewer oscillators can be active at the same time. Tape

Loops should not be used because of limitations of data

transmission across the ISA Bus.

Wave Pointer Lo

address 6

ROM0-ROM7

bits 0-7

The eight bits of Wave Pointer Lo are part of the wave ad-

dress that is modified by the oscillator through the life of

the note as it steps from sample to sample, based on fre-

quency, corresponding to ROM or RAM address bits 0-7.

The upper bits of the wave ROM address are set at initial-

ization and remain fixed (Wave Pointer Hi). Wave Pointer

Lo points to a sample in ROM or RAM. (Refer to Phase

and Wave Pointer Mid.) Wave Pointer Lo contains the low-

est bits of the start address when a note is begun. Wave

Pointer Lo and Wave Pointer Mid are changed by the

Z89340 during the life of a sound until they equal Wave

Endpoint.

Wave Pointer Mid

address 7

ROM8-ROM15

bits 0-7

The eight bits of Wave Pointer Mid point to a block of 256

samples. This 256 sample block can be considered a

wavetable for use in wavetable synthesis. For sample-se-

quence playback, Wave Pointer Mid forms the upper eight

bits of the 16-bit sample pointer; Wave Pointer Lo holds

the lower eight bits. This allows sample sequences of up

to 64K samples. Wave Pointer Mid contains eight bits of

the start address when a note is begun. Wave Pointer Lo

and Wave Pointer Mid are changed by the Z89340 during

the life of a sound until they equal Wave Endpoint.

Wave Endpoint Lo

address 8

ATFP Flags

bits 0 and 1

These bits are active for the selected envelope types in

Frequency Lo. The bits have a separate meaning for

Tremolo from the other types.

Amplitude/Filter/Pan envelope flag bits:

00-Off

01-Wait

10-In process

11-Done

Tremolo envelope flag bits:

bit 0-Enable

bit 1-Polarity

ROM2-ROM7

bits 2-7

Wave Endpoint is the last sample in the delay line. When

this last sample location is used, the Z89340 subtracts

Wave Loop Length from the Wave Pointer. Note that since

only six bits are available for Wave Endpoint Lo, the sam-

ple sequence can only end on every fourth address. Wave

Loop Length does not have this restriction.

Wave Endpoint Hi

address 9

ROM8-ROM15

bits 0-7

(Refer to Wave Endpoint Lo.)

Wave Loop Length Lo

address A

Table Size

bits 0 and 1

(Wavetable Mode Oscillator only)

With wavetable synthesis, one or more complete periods

of a waveform are stored in a wavetable. Table Size is the

size of the wavetable. Interleave is the distance between

wavetables. Normally Interleave Size will equal Table Size

so that the wavetable will be contiguous. For compatibility

with existing sound libraries, other interleaves are avail-

able.

00-64 Samples

01-128 Samples

10-256 Samples

11-512 Samples

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