Spectravideo MKI, Сервисное – Техническое руководство

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To i n p u t da t a f rom I / O P o r t A to the
CPU
b u s
wou l d re qu i re the fo l l ow i ng :
1 .
La t c h a dd r e s s R7 ( s e l e c t Enab l e
re g i s t e r )
2 . Wr i te da t a t o PSG ( s e l e c t B6 t o R 7
r:o
''0" )
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 g
i
s
t
e
r
)
4 .
R e a d da t a f rom PSG ( d a ta f rom I /0
Port A )
N o t e t h a t once l o • d e d w i t h dat a i n the i n p u t mo d e , the d a t a w i l l rema i n on the
I / 0 Por t s un t i l changed e i t h e r by l o a d ing
d i f f e r e n t
d a t a , by app l y ing a r e s e t
( g r o und ing t he Re s e t p i n ) , o r b y sw i tch ing
to
t he i nput mode .
AY-3-8 9 1 0
P ROGRAM�� BLE S OUND GENERATOR
P IN
ASS IGNMENTS
DA -- DAO
( i npu t / ou t p u t / h i gh i mpe ndance ) : p i n s 30--3 7
The s e 8 l i n e s comp r i se t he 8-b i t b i d i r e c t i on a l b us u s e d by the m i c rop r oc e s sor
to se nd bo th da t a and a dd re s s e s t o the
PSG
and to rec e i ve da t a f rom the
P S G .
I n
t he
da ta mod e , DA7 --DAO c o r r e s p ond t o Reg i s t e r A r ray b i t s B 7 --BO . I n the
a dd re s s mod e , DA3 --DAO s e l ec t the 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
o r d e r
a d d r e s s ( c h ip
se l ec t ) .
AB ( i nput )
p i n 2 5
A9 ( i npu t ) p i n
24
A dd r e ss 9 , A dd r e s s 8
T he s e "ex t r a " add re s s b i t s a r e ma d e ava i l a b l e to enab l e the pos i t i o n i ng of the
PSG ( a s s i g n ing a 16 word memory space ) in a t o t a l 1 , 024 word memory a re a r a t he r
t h a n i n
a
2 5 6 wor d memor y a r e a as d e f i n e d by add r e s s b i t s DA 7 --DAO a l one . I f
t he memor y s i ze does n o t re q u i re t h e u se o f t h e s e ex t ra a dd re s s l i nes they ma y
be l e f t unconne c t tl d a s e a ch i s p ro v i d e d H i t h e i t h e r an on-ch ip pu l l down (A9 )
or pu l l - up ( AS ) re s i s t o r .
In "no i s y" envi ro nmen t s , howeve r , i t i s rec ommended
t h a t A9 and AS be t ie d t o an ex t e rna l g round and +5V , r e s p ec t i ve l y , i f they a re
no t t o be us e d .
RESET
( i npu t ) p i n 2 3
F o r i n i t i a l i z a t i on / powe r-on pu rpos e , a log ic
"0"
( g r ound ) to the Re s e t
p i n w i l l re s e t a l l reg i s t e r s to
110" .
The Re s e t p i n is p rov i d e d w i th an on-c h ip
pu l l - up res i s t o r .
CLOCK
( i nput ) p i n
22
Th i s TT L-compa t i b l e input supp l i e s the t i m ing re fe r e nce for the Tone , N o i s e and
Enve l ope Gene ra t o rs .
BD I R , BC2 , BC 1 ( input s )
p i ns
2 7 ,
28 , 29
4 . 48