Sound Generator - Spectravideo SVI 318 Service – Technical Manual

SOUND GeNERATOR

PROGRAMMAB L E
T h e AY-3 -8 9 1 0
i s a r� g i s t e r o r i e n t e d
Commun i c a t i o n b e t w e e n
1 / 0 .
me mo r y-ma p pe d
me mo r y -m a p p e d reg i s t e r s .
so t h a t t h e m i c r o p r o ce s s o r
r e a d a b l e
o r s t o re d da t a va l u e � .
A l l f u n c t i on s o f t h e P S G a r e co n t r o l l e d
p ro g ramme d , g e n e r a t e and s u s t a i n th e
f o r o t h e r t as k s .
SOU N D
GENERAT ING BLOCK
B a s i c
The B l o c k s in the PSG wh i c h p ro d u c e
Tone G e n e ra t o r s
N o i s e G e n e ra t o r
M i x e rs
Amp l i t ud e Con t r o l
E nve l o pe G e n e r a t o r
Conve r t e r s
0 / A
To ou t p u t da t a f rom t h e C PU bus to a pe r i p he ra
A w ou ld re qu i re on ly t he f o l low ing s t e p s :
La t c h a dd re s s R 7 ( se l e c t Enab l e reg i s t e d
1 .
2 . W r i t e da t a t o PSO ( se t t i ng B6 o f R 7 to
3. La t c h a dd re s s
4 . Wr i t e dat a t o PSG ( d a t a t o be ou t p u t o n I / 0 P o r t A )
AY-3-89 1 0
t h e
p r o c � s s o r
Co n t r o l comma n d s a r e
Each o f the
p r oduce t h e
e a ch cha nne l
p roduce a f re q u e n c y m o d u l a t e d p s e udo random pu l s e
w i d th s qua r e
comb i ne t h e ou t p u t s o f the T o ne G e n e r a t o r s and t h e
N o i s e G e n e r a t o r .
p rov i d e s t h e
va r i a b l e amp l i t u d e pa t t e r n .
und e r d i r e c t C P U c o n t r o l l t he va r i ab l e amp l i t u de i s
accomp l i sh e d b y u s i n g t h e ou t p u t o f t h e E nve l op e
G e n e r a t o r .
p ro d u c e s a n enve l o p e pa t t e r n w h i c h can b e u s e d t o
amp l i t ud e m o d u l a t e t he ou t p u t bf e ach m i x e r .
the three D/A Conve r t e r s e a c h p ro d u c e up t o a
l e ve l ou t pu t s i g n a l a s d e t e rm i ned by t he Amp l i t ude
Coot ro l .
( s e l e c t 20A reg i s t e r )
R 1 6
4 .4 7
sou n d g e n e r a t o r ( PS G ) .
p r o g r a mm a b l e
P S G
and
i s s u e d
t h e i s ba s e d
to
t h e
1 6
r e g i s t e r s w i t h i n the PSG i s a l s o
a s ne c e s s a r y , p re s e n t s t a t e s
c a n d e t e r m i n e ,
1 6
i t s
t h r o u g h
f r e e i n g the s y s t e m p roc e s s o r
s o u n d s , t h u s
t h e
p r o g ramme d soun d s i nc l u d e :
b a s i c
s q u a re wave t o ne f re qu e n c i e s for
( A , B ,
C ) .
wave
ou t p u t .
One f o r e a c h channe l ( A , B , C ) .
c o n n e c t o r s w i th e i t he r a f ix e d o r
D / A
1
d ev i c e connec t e d t o
" 1 " )
on the conce p t o f
P S G by
w r i t i ng t o
r e g i s t e r s wh i c h once
T h e f i x e d amp l i t ude i s
1 / 0
P o r t
16
16