z8934050fsc ZiLOG Semiconductor, z8934050fsc Datasheet - Page 27

• Manufacturer Part Number: z8934050fsc
• Description: Digital Wavetable Engine
• Manufacturer: ZiLOG Semiconductor

ROM2-ROM7
(Wavetable Mode Oscillator only)
For Wavetable Mode Oscillators this should be 0.
ROM0-ROM7
(Sample Loop Oscillator only)
A sample sequence is played by setting Wave Pointer to
the first sample in the sequence and Wave Endpoint to the
last sample in the sequence. For many sounds, we then
repeat or loop the last portion of the sequence. Wave Loop
Length is the length of the loop.
Wave Loop Length Hi
ROM8-ROM15
(Refer to Wave Loop Length Lo.)
For Wavetable Mode Oscillators this should be 0.
Effects Send Control
Effects Attenuation(s)
These six bits control the amount of signal that will be sent
to the selected Effects Channel (bits 6-7). Since the signal
will be sent to two effects output channels if the Dual Effect
Sends bit in the Control Byte is set, the Effects attenuation
splits into two three-bit attenuation values, with bits 0-2 as
the attenuation for the channel selected by the Effects
Channel, and bits 3-5 as the attenuation for the subse-
quent channel.
Effects Channel
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,
the signal will be sent to two effects channels, the one se-
lected here and the subsequent channel.
Envelope rate
When ATFP selects Amplitude, Filter, or Pan:
Envelope Rate
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
The four bits of Rate are an unsigned exponential number
that give rates ranging from 0.1 to 10 Hz.
DS96DSP0201
address B
address C
address D
bits 2-7
bits 0-7
bits 0-7
bits 0-5
bits 6-7
bits 0-7
bits 0-3
P R E L I M I N A R Y
Tremolo Depth
These four bits specify depths of 1.5 to 24 decibels.
Amp/Filt/Pan Next
When ATFP selects Amplitude:
Amplitude Next
Amplitude is expressed in an unsigned logarithmic unit
called a hexadecibel or “hexabel” for short. The upper four
bits of the hexabel are a base-two exponent and the lower
four bits form the mantissa. There are 256 hexabel steps
in 96 decibels, so 2.667 hexabels = 1 decibel. At the initial-
ization of a note, set Amplitude Now and Amplitude Next
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
Next at the end of an envelope segment.
When ATFP selects Filter:
Filter Tuning Next
Filter Tuning Next works in a way similar to Amplitude
Next.At the initialization of a filter envelop segment, set Fil-
ter Tuning value and Filter Tuning Next with the endpoints
of the filter envelope segment. Also set the Envelope Rate.
When ATFP selects Pan:
Pan Angle Next
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.
Pan Direction
A 1 indicates counterclockwise rotation, and a 0 indicates
clockwise rotation.
Pan Continuous Loop
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
(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.
Digital Wavetable Engine
address E
address F
bits 4-7
bits 0-7
bits 0-7
bits 0-5
bits 0-7
bit 6
bit 7
Z89340
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