Z89340 Datasheet, PDF (27/30 Pages) Zilog, Inc. – Digital Wavetable Engine

Z89340
Digital Wavetable Engine
ROM2-ROM7
bits 2-7
Tremolo Depth
bits 4-7
(Wavetable Mode Oscillator only)
These four bits specify depths of 1.5 to 24 decibels.
For Wavetable Mode Oscillators this should be 0.
Amp/Filt/Pan Next
address E
1
ROM0-ROM7
bits 0-7
(Sample Loop Oscillator only)
When ATFP selects Amplitude:
A sample sequence is played by setting Wave Pointer to Amplitude Next
bits 0-7
the first sample in the sequence and Wave Endpoint to the Amplitude is expressed in an unsigned logarithmic unit
last sample in the sequence. For many sounds, we then called a hexadecibel or “hexabel” for short. The upper four
repeat or loop the last portion of the sequence. Wave Loop bits of the hexabel are a base-two exponent and the lower
Length is the length of the loop.
four bits form the mantissa. There are 256 hexabel steps
Wave Loop Length Hi
address B
in 96 decibels, so 2.667 hexabels = 1 decibel. At the initial-
ization of a note, set Amplitude Now and Amplitude Next
ROM8-ROM15
bits 0-7
(Refer to Wave Loop Length Lo.)
For Wavetable Mode Oscillators this should be 0.
with the endpoints of an amplitude envelope segment.
Also set the Envelope Rate. For subsequent amplitude en-
velope segments, only set Amplitude Next and Envelope
Rate, because Amplitude Now always equals Amplitude
Effects Send Control
address C
Next at the end of an envelope segment.
Effects Attenuation(s)
bits 0-5
When ATFP selects Filter:
These six bits control the amount of signal that will be sent Filter Tuning Next
bits 0-7
to the selected Effects Channel (bits 6-7). Since the signal Filter Tuning Next works in a way similar to Amplitude
will be sent to two effects output channels if the Dual Effect Next.At the initialization of a filter envelop segment, set Fil-
Sends bit in the Control Byte is set, the Effects attenuation ter Tuning value and Filter Tuning Next with the endpoints
splits into two three-bit attenuation values, with bits 0-2 as of the filter envelope segment. Also set the Envelope Rate.
the attenuation for the channel selected by the Effects
Channel, and bits 3-5 as the attenuation for the subse- ^{When ATFP selects Pan:}
quent channel.
Pan Angle Next
bits 0-5
Effects Channel
bits 6-7
These two bits are used to select one of four effects output
channels. These output channels can be used internally by
the Z89340, and they can also be sent to a DAC or CO-
DEC. If the Dual Effect Sends bit in the Control Byte is set,
Pan Next works in a way similar to Amplitude Next or Filter
Tuning Next, except that there are only six bits of pan po-
sition. At the initialization of a pan segment, set Polar Pan
Angle and Pan Angle Next with the endpoints of the pan
envelope segment. Also set the Envelope Rate.
the signal will be sent to two effects channels, the one se-
lected here and the subsequent channel.
Pan Direction
bit 6
A 1 indicates counterclockwise rotation, and a 0 indicates
Envelope rate
address D
clockwise rotation.
When ATFP selects Amplitude, Filter, or Pan:
Envelope Rate
bits 0-7
With Amplitude, the eight bits of Envelope Rate are an un-
signed exponential representation of the slope between
the amplitudes at the two envelope segment ends. This is
the rate that defines how long it will take to reach the end
amplitude, Amplitude Next. An interrupt is generated when
the segment end is reached, at which time the host CPU
will set up the next amplitude segment, supplying a new
Amplitude Next value and Envelope rate. A similar proce-
dure is followed when ATFP selects Filter or Pan.
When ATFP selects Tremolo:
Tremolo Rate
bits 0-3
The four bits of Rate are an unsigned exponential number
that give rates ranging from 0.1 to 10 Hz.
Pan Continuous Loop
bit 7
If this bit is a 0, an interrupt is generated to let the host CPU
know that the panning has completed. If this bit is set, pan
continues around this circle indefinitely. No interrupt is
generated when Pan Angle Next is reached.
Amplitude Now
address F
bits 0-7
(Refer to the previous discussion on Amplitude Next.)
If ATFP amplitude envelopes are not being used, this will
be the amplitude of the oscillator—a steady or sustained
amplitude segment. Amplitude Now can be changed
whenever desired; however, changing Amplitude Now
more than 1 hexabel will usually cause a noticeable click.
Even a 1 hexabel change will sometimes cause a click. To
eliminate clicks or zipper noise, use the amplitude enve-
lope system.
DS96DSP0201
PRELIMINARY
1-27