Z89340 datasheet(21/30 Pages) ZILOG

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Z89340

Digital Wavetable Engine

DS96DSP0201

P R E L I M I N A R Y

1-21

Input Data Streamer

Samples can be moved via DMA from the CPU host RAM

to the Z89340 wavetable RAM space. Up to 48 channels

of bus-mastered DMA are available (Figure 15).

OSCILLATOR PARAMETER BLOCKS

An oscillator is controlled by the host CPU by writing com-

mands in the on-chip RAM that is associated with the os-

cillator. This RAM is called the Oscillator Parameter Block.

The following pages present, for each of the oscillator

types, a description of the bit fields in the 24 bytes of the

Oscillator Parameter Block. Address 0 in the block is the

Control Byte.

The two bits of Oscillator Type deserve special mention.

Extended Opcodes are enabled when both of these bits

are set, and the high four bits of Frequency Hi specify

which extended opcode to use. Because the Sample Loop

and Wavetable Mode oscillators are so similar, they are

presented together. The Wavetable Mode oscillator, how-

ever, is an extended opcode.

Sample Loop/Wavetable Mode Oscillators

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-

nels-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 is un-

available that would be used as their half-speed counter-

parts.

Oscillator-type

bits 6-7

These bits define the operating mode of the oscillator:

00-If all 8 bits of the Control Byte are 0, the oscillator shuts

off completely regardless of the settings of the other pa-

rameters. To prevent an oscillator from sending output to

any channel without shutting it down, use the special si-

lence command in the Polar Pan control.

01-8-bit linear PCM wavetable data.

10-16-bit linear PCM wavetable data.

11-extended opcode. For Wavetable Mode, set the upper

four bits of Frequency Hi to 0100.

Figure 15. The Input Data Streamer Address Map

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