Z89340 Datasheet, PDF (28/30 Pages) Zilog, Inc. – Digital Wavetable Engine

Z89340
Digital Wavetable Engine
OSCILLATOR PARAMETER BLOCKS (Continued)
Polar Pan Control
address 10
Polar Pan Angle
bits 0-5
There are four main output channels. The spatial location
among them is specified with a modified polar coordi-
nate—a value of 16 is π/2 radians, 32 is π radians, 48 is
3π/2 radians, and so on.
Polar Pan Radius
bits 6-7
The radius select is a two-bit number with 2 at the edge of
the circle and 0 near the center of the circle. A radius of 3
is reserved for stereo panning when only two output chan-
nels are needed. When the radius is 3, the following spe-
cial values of Pan Polar Angle are defined:
0-f
20-2f
3d
3e
3f
stereo pan FRONT channels left to right.
stereo pan REAR channels left to right.
instead of sending to the output channels, output
is sent to one of 32 submix registers. The submix
register is chosen with low five bits of the Effects
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.
Filter Tuning Value
address 11
Vibrato Depth
bits 4-6
These three bits specify depths ranging from plus and mi-
nus a few cents to about 1 semitone.
Clear Submix
bit 7
Set this bit when this oscillator should clear the submix
register before placing an output value in it.
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 accumu-
lator to 128 corresponding to π radians, a zero crossing in
the sinewave just before it swings negative.
Delay 1A
Delay 1B
Delay 2A
Delay 2B
address 14
address 15
address 16
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.
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.
1-28
PRELIMINARY
DS96DSP0201