If
(wave = triangle)
write
AUDOLCL
with address of sine wave data.
Else if (wave = sine)
write
AUDOLCL
with address of triangle wave data.
Main
Program
1.
Set up volume, period, and length.
2.
Write
AUDOLCL
with address of sine wave data.
3.
Start
DMA.
4. Continue with something else.
System
Response
As soon as
DMA
starts,
a. Copy to "back-up" length register from
AUDOLEN.
b. Copy to "back-up" location register from
AUDOLCL
(will
be
used as a pointer
showing current
data
word to fetch).
c. Create an interrupt for the 68000 saying
that
it
has completed retrieving work-
ing copies of length and location registers.
d.
Start
retrieving audio
data
each allocated
DMA
time slot.
148 Audio Hardware
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