Z89340 Datasheet, PDF (25/30 Pages) Zilog, Inc. – Digital Wavetable Engine

Z89340
Digital Wavetable Engine
0-f stereo pan FRONT channels left to right.
20-2f stereo pan REAR channels left to right.
Oscillator Parameter Block for the Tape Loop
Oscillator
3d sent to one of 32 submix registers. The submix
Control Byte
register is chosen with low five bits of the Effects
address 0
1
Send Control. Submix registers can be selected
Filter Q
bits 0-3
as inputs by Tape Loop oscillators (an extended
Each oscillator has a variable filter. These bits allow ad-
opcode).
justment of the filter Q. (Refer to Filter Tuning value for
3e mute the oscillator. The oscillator continues to do more information.)
everything else except connect to an output
channel.
Dual Effect Sends
bit 4
3f
sends output to all four output channels equally,
When this bit is set, the oscillator talks to two effect chan-
effectively at the center of the circle.
nel, so the effect channel chosen with Effect Channel in
the Effect Send Control Byte, and the subsequent channel
Filter Tuning Value
address 11
(wraps to effects channel 0 if the last channel is chosen).
This system allows choosing two of the four effects chan-
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.
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).
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.
Vibrato Depth
bits 4-7
These four bits specify depths ranging from plus and mi-
nus a few cents to about two semitones.
Vibrato Phase
Accumulator
address 13
Oscillators 48 through 63 (0x30 through 0x3f) can only op-
erate at the full clock rate since the parameter RAM that
would be used as their half-speed counterparts is unavail-
able.
Oscillator-type
bits 6-7 11-extended
opcode
These bits define the operating mode of the oscillator.
Since Tape Loop is an extended opcode, both bits will be
set to 1. For Tape Loop, set the upper four bits of Frequen-
cy Hi to 0000.
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 Accu-
mulator 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
Frequency Low
address 1
Envelope-type ATFP
bits 0 and 1
Four types of envelope segments are supported, but only
one at a time. Amplitude/Tremolo/Filter/Pan Envelope-
type control bits.
00-Amplitude
01-Tremolo
10-Filter
11-Pan
Frequency Low
Always 0 for Tape Loop.
bits 2-7
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.
Frequency Mid
Always 0 for Tape Loop.
address 2
bits 0-7
DS96DSP0201
PRELIMINARY
1-25