Spectravideo SVI 318 Service – Technical Manual page 81

T o i n p u t da t a f rom I / O P o r t A to t h e CPU
1 .
La t c h a dd r e s s R7 ( s e l e c t E n a b l e
2 . W r i t e d a t a t o PSG ( s e l e c t B6 t o R 7
3 .
La t c h a dd r e s s R 1 6 ( s P l e c t l O A
R e a d da t a f rom PSG ( d a ta f rom I / 0 P o r t A )
4 .
N o t e t h a t o n c e l o • d e d w i t h d a t a i n t h e i n p u t mo d e , the d a t a w i l l rema i n on the
I / 0 P o r t s un t i l c h a n g e d e i t h e r b y l o a d i n g
( g r o u n d ing t he Re s e t p i n ) , o r b y sw i t c h ing to t he i n p u t mode .
A Y - 3 -8 9 1 0 P ROGRAM�� BLE S OUND GENE RATOR P I N A S S I G NMENTS
DA -- DAO ( i n p u t / ou t p u t / h i gh i mp e n d a n c e ) :
T h e s e 8 l i n e s comp r i s e t he 8 - b i t b i d i r e c t i o n a l b u s u s e d by the m i c rop r o c e s s o r
t o s e nd bo t h da t a and a dd re s s e s t o t h e P S G a n d t o rec e i ve da t a f rom the P S G . t he
I n d a t a mod e , DA7 -- DAO c o r r e s p on d t o R e g i s t e r A r r a y b i t s B 7 --BO .
a dd re s s mo d e , DA3 -- DAO s e l e c t t h e reg i s t e r # ( 0 -- 1 7 ) and DA7 --DA4 i n
c on j un c t i on w i th a dd re s s i n p u t s A9 and A 8 f o rm t he h i gh
s e l e c t ) .
AB ( i n p u t ) p i n 2 5
A9 ( i n p u t ) p i n 2 4
A dd r e s s 9 , A dd r e s s 8
T he s e " e x t r a " add re s s b i t s a r e ma d e a va i l a b l e to enab l e t h e p o s i t i o n i ng o f the
a
PSG ( a s s i g n ing a 16 word memory s p a c e ) in a t o t a l 1 , 0 24 w o r d memory a re a r a t he r
t h a n i n
2 5 6 wor d me mo r y a r e a as d e f i n e d b y a d d r e s s b i t s DA 7 -- DAO a l one .
t he memor y s i ze d o e s n o t re q u i re t h e u s e o f t h e s e ex t ra a dd r e s s l i n e s t h e y ma y
be l e f t unc onne c t tl d a s e a c h i s p ro v i d e d H i t h e i t h e r an on-ch i p pu l l down ( A9 )
or pu l l - up ( AS ) re s i s t o r .
t h a t A 9 a n d AS be t ie d t o a n ex t e rna l g r ound and +5V , r e s p ec t i ve l y , i f t h e y a re
no t t o be u s e d .
R E S E T ( i np u t )
F o r i n i t i a l i z a t i on / powe r-on pu r p o s e , app l y ing a log i c
p i n w i l l re s e t a l l reg i s t e r s to
pu l l - up r e s i s t o r .
CLOCK ( i n p u t )
T h i s TT L- compa t i b l e i n p u t s u pp l i e s the t i m i n g re f e r e nc e for the Tone , N o i s e and
Enve l o pe Gene ra t o rs .
BC 1
BD I R , BC2 ,
( i nput s )
re g i s t e r )
i
e g
r
In " no i s y" e n v i r o nme n t s , howeve r , i t i s re c omme n d e d
p i n 2 3
1 1 0 " .
p i n 2 2
p i n s 2 7 , 2 8 , 2 9
4 . 48
b u s
wou l d re qu i r e the fo l l ow i ng :
r:o
' ' 0 " )
s e
)
t r
d i f f e r e n t
d a t a , b y app l y i n g a r e s e t
p i n s 3 0 --3 7
"0"
The Re s e t p i n i s p rov i d e d w i th a n on-c h ip
I n the
a d d r e s s ( c h i p
o r d e r
( g r ound ) to the Re s e t
I f