Spectravideo SVI 318 Service – Technical Manual page 117

F o r
r ea d o p e r a t i o n s ,
p u l s e pe r f l u x t r a n s i t i on and
n s
a 2 5 0
i f
f l ux t r a n s i t i on s p a c i n g s .
u t
b no t i t ma y be
u n t
c o e r t e c h n i qu e s .
2 5 ) wh i c h
( P i n c a n b e
r o e
s y n c h r o n i z a t i on . Wh e n
o f e h
b y t e s z s a r e d e t e c t e d .
ne x t 1 0 b y t e s ; o t
e
t r
be g i n s a l l o v e r ag a i n .
as t h e
u e a s l on g
S i m i l a r l y for
s t r e am .
d e t e c t e d . T he FD f 7 93
o t h e r w i s e i s re s e t a
RG
Du r i ng re a d ope r a t i o n s
l o op
s y n c h ro n i z a t i on .
HLT and
( a ) Bo t h HLD a r e T r u e
S e t in T i m e , if
( b ) t g
( c )
th e i s i n sp e c t i ng d a t a o f f the
1 7 9 3
I f
i s no t u s e d , l e a v e op e n or
WF /VFOE
D I S K WR I T E O P E RAT I ON
Whe n w r i t i ng i s
t o
a v t d ,
c t i a e a l low ing cu r r e n t t o
t
o e r r o n e o u s w r i t i ng t h e f i r s t d a t a b y t e mus t b e l o a d e d i n t o
t o
i n r e s p o n se
a D a t a R e q u e s t
be a c t i va t e d .
W r i t ing
W r i t e i i nh i b i te d wh en
s
r
an y command i s
n
i s t a t us b i t i s s e t .
i
W t e P r o t e c t
a u e
i
s g i f e s a w r i t i ng f a u l t
l d e t e c t wr i t e c u rre nt f low when t h e Wr i t e G a t e i s a c t i va t e d .
f i r t o
d e t e c t i on o f th i s f au l t t he FD1 7 93 t e rm i n a t e s t he cu rrent command , a n d s e t s t h e
W r i t e
b i t ( b i t 5 ) i n t h e S ta t u s Wor d .
Fa u l t
ma d e i na c t i ve wh en t he
F o r w r i t e ope r a t i o ns , t h e
ou t p u t s .
( P i n
3 1 )
1 ) and 2 50 ns p u l s e s i n MFM ( DDEN
( D DEN
=
a dd re s s ma rks i n bo t h f o rma t s .
t h e FD 1 7 9 3 r e q u i r e s RAW READ
T h e R C LK ( P in
d e r i v e d e x t e r n a l l y b y
a
I n a d d i t i on , R e a d G a t e
u s e d t o i n f o rm pha s e
f r om
r e a d i n g t h e me d i a
rw
T h e F D 1 7 9 3
i s e R G i s r e s e t a n d t he
I f a n a d d r e s s ma rk
FD 1 7 93 i s d e r i v i ng
a d
i s m
MFM , RG e
c
m u s t f i nd an a dd re ss mark w i t h in t he ne x t 1 6 b y t e s , r
r h e s u
a
n d s e m
0 ) , t h e
( WG VFOE
=
w i l l a c t i ve whe n :
go
V F O E
h a s e x p i re d
p ro g r amme d ,
t h e
t a k e p l a ce on d i sk e t t e
f l ow i n t o t he Read / Wh i t e
f rom t h e
mme
t he t W r i t e y P r
i di e
a l t e rm i na t e d ,
The
c o n d i t i o n
de t e c t e d
Wr i t e Ga t e ou t p u t b e comes i n a c t i ve .
p ro v i d e s Wr i t e G a t e ( P i n 3 0 ) and Wr i t e Da t e
F D 1 7 9 3
Wr i t e d a t a c o n s i s t s o f a se r i e s o f 500 n s pu l s e s i n
4 . 84
D a t a ( P i n
c l ock
a R e a d ( RCLK )
2 6 ) i s
s ig n a l p ro v i d e d b y
P h a s e l o c k l oop s ,
n a p rov i de d as an ou t p u t
S i g l is
l o o p s
l o c k wh e n
i n RG i s
FM ,
mus t
f i n d an a dd r e s s
s e a rc h for 2
found w i t h i n 1 0
i s
i n f o rma
u s e f u l
an y
a c t i ve whe n 4
b y t e s
e .
s
( P i n 3 3 ) i s prov i d e d f o r pha s e l ock
d i s k
a l OK res i s t o r to + 5 .
t i e to
the W r i t e Ga t e
h ea d .
e f re
b o t h e
F D 1 7 9 3
o t t i n p u t i s a l o g i c
e c
a n i n t e r r u p t
Wr i t e Fa u l t i n pu t , wh en a c t i va t e d ,
i n d i sk dr ive e l e c t r o n i c s suc h a s
T h e Wr i t e Fa u l t i np u t shou l d b e
0). Wr i te D a ta p ro v i d e s the u n i qu e
=
2 7 ) s i g na l
wh i c h
t o ind i c a t e
s i gna l
s ome d r i ve s
o sho t s , or
n e
u re
to c q i
a
true whe n 2
ma d e
ma r k w i t h i n t h e
b y t e s o f z e roe s
rema i n s
b y t e s , RG
f rom t he d a t a
t i o
n
o f "00" a re
o r
" F F "
ou tpu t i s
( WG )
As a p r e ca u t i on
t h e Data Reg i s t e r
W r i t e G a te s ig n a l can
low, i n wh i c h c a s e
e a t e a n d t he
i s g e n r d
O n
FM
i s