Microchip Technology ay-3-8910 - Noise Only Effects

6.2 Some of the more commonly required sounds require only the use of
Noise Only
noise and the envelope generator (or processor control of channel
envelope if other channels are using the envelope generator).
Effects
Examples of this, which can be seen in Figs. 28 and 29, are gunshot
and explosion. In both cases pure noise is used with a decaying
envelope. In the examples shown the only changes are in the length
of the envelope as modified by the coarse tune register and in the
noise period. Note that a significantly lower explosion can be
obtained by using all three channels operating with the same
parameters.
Fig. 28 GUNSHOT SOUND EFFECT CHART
Octal
Register # Load Value
Explanatlon
Any not specified
000
R6
017
Set Noise period to mid-value.
R7 007
Enable Noise only on Channels A,B,C.
RlO
020
Rll
020
Select full amplitude range under direct
R12
020
control of Envelope Generator.
R14
020
Set Envelope period to 0.586 seconds.
R15
000
Select Envelope “decay”, one cycle only.
Fig. 29 EXPLOSION SOUND EFFECT CHART
Register #
Any not specified
R6
R7
R10
R11
R12
R14
R15
Octal
Load Value
Explanation
000
000
Set Noise period to max. value.
007
Enable Noise only, on Channels A,B,C.
020
020
Select full amplitude range under
020
direct control of Envelope Generator.
070
Set Envelope period to 2.05 seconds.
000
Select Envelope “decay”, one cycle only.