Z89340 Datasheet, PDF (21/30 Pages) Zilog, Inc. – Digital Wavetable Engine

Z89340
Digital Wavetable Engine
Input Data Streamer
Samples can be moved via DMA from the CPU host RAM of bus-mastered DMA are available (Figure 15).
to the Z89340 wavetable RAM space. Up to 48 channels
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Figure 15. The Input Data Streamer Address Map
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.
DS96DSP0201
PRELIMINARY
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