The
lengths of the
data
sets of the modulator and the modulated channels are
com--
pletely independent.
Channels are attached by the system in a predetermined order, as shown in table 5-5.
To
attach
a channel as a modulator, you
set
its
attach
bit
to
1.
If
you
set
either
the
volume
or
period
attach
bits for a channel,
that
channel's audio
output
will be disabled;
the channel will be attached
to
the next higher channel, as shown in table 5-5. Because
an attached channel always modulates
the
next higher numbered channel, you cannot
attach
channel 3. Writing a 1 into channel 3's modulate bits only disables its audio out-
put.
Table 5-5: Channel Attachment for Modulation
ADKCON
Register
Bit
Name Function
7 ATPER3
Use audio channel 3
to
modulate nothing
(disables audio
output
of channel 3)
6 ATPER2
Use audio channel 2
to
modulate period
of channel 3
5
ATPERI
Use audio
channell
to
modulate period
of channel 2
4 ATPERO
Use audio channel 0
to
modulate period
of
channell
3 ATVOL3
Use audio channel 3
to
modulate nothing
(disables audio
output
of channel 3)
2 ATVOL2
Use audio channel 2
to
modulate volume
of channel 3
1 ATVOLI
Use audio
channell
to
modulate volume
of channel 2
0
ATVOLO
Use audio channel 0
to
modulate volume
of
channell
Audio Hardware 151
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