Z89340 Datasheet, PDF (26/30 Pages) Zilog, Inc. – Digital Wavetable Engine

Z89340
Digital Wavetable Engine
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.
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
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
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
(Refer to Wave Endpoint Lo.)
bits 0-7
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
1-26
PRELIMINARY
DS96DSP0201