Commodore 128 Programmer's Reference Manual page 372

362 COMMODORE 128
Bits 0-3 (RLS0-RLS3) select 1 of 16 RELEASE rates for the Envelope Genera
tor. The RELEASE cycle follows the SUSTAIN cycle when the Gate bit is reset to zero.
At this time, the output of Voice 1 will fall from the SUSTAIN amplitude to zero
amplitude at the selected RELEASE rate. The 16 RELEASE rates are identical to the
DECAY rates as listed in Figure 11-14.
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NOTE: The cycling of the Envelope Generator can be altered at any
point via the Gate bit. The Envelope Generator can be gated and re
leased without restriction. For example, if the gate bit is reset before the
envelope has finished the ATTACK cycle, the RELEASE cycle will
immediately begin, starting from whatever amplitude had been reached.
If the envelope is then gated again (before the RELEASE cycle has
reached zero amplitude), another ATTACK cycle will begin, starting
from whatever amplitude had been reached. This technique can be used
to generate complex amplitude envelopes via real-time software control.
VALUE ATTACK RATE
DECAY/RELEASE RATE
DEC (HEX)
(TIME/CYCLE) TIME/CYCLE)
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
(0)
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
(9)
(A)
(B)
(C)
(D)
(E)
(F)
2 ms
8 ms
16 ms
24 ms
38 ms
56 ms
68 ms
80 ms
100 ms
250 ms
500 ms
800 ms
Is
3s
5s
8s
6 ms
24 ms
48 ms
72 ms
114 ms
168 ms
204 ms
240 ms
300 ms
750 ms
1.5 s
2.4 s
3s
9s
15 s
24s
NOTE: Envelope rates are based on a 1.0-MHz 02 clock. For other 02
frequencies, multiply the given rate by 1 MHz/02. The rates refer to the
amount of time per cycle. For example, given an ATTACK value of 2,
the ATTACK cycle would take 16 ms to rise from zero to peak ampli
tude. The DECAY/RELEASE rates refer to the amount of time these
cycles would take to fall from peak amplitude to zero.
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Figure 11-14. Envelope Rates
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