Spectravideo MKI, Сервисное – Техническое руководство, Страница: 126 / 134

2 2
2 3
2 5
2 5
26
27
28
29
TEST
HEAD LOAD T IMING
READ GATE
( 1 79 1 / 3 )
S I DE SELECT
OUTPUT ( 1 79 5 ,
1 7 9 7 )
READ CLOCK
RAW
READ
HEAD
LOAD
TRACK GREATER
THAN 43
TEST
HLT
RG
s so
RCLK
RAW READ
HLD
TG43
4 . 93
Th i. s i Tlput i s us e d f o r t e s t i ng J ' u r ­
p .Yc c s
only
a n d sh ou l d be t ie d tu + 5 V
o r
l e f t o p e n by t h e u s e r un l e s s int e r ­
f" ,·
. .
:: f -1.:; to
voi�":e (' O i l act uated
m•
t o r s .
When
a
log i c h i gh i s f o und on tl e
HLT
i np u t the head is n s s ume d to
be
engage d .
A h i gh l e ve l on th i s ou t pu t i n d ca t e s
t o the d a t a s e p a r a t o r c i rc u i t ry tha :
a f i e l d of z e ro s ( o r ones ) h a s I e e n
enc o u n t e re d , and i s u s e d fo r
s y nchron i c z a t f on .
T he log i c l e ve l o f t he S ide Se l < c t
Ou t p u t i s d i r e c t l y con t ro l l e d b)
t � �
' S '
f l ag i n Type
I I
o r
I I I
comm< nds .
W h
e n
S -
1 ,
SSO i s s e t t o a l o g c 1 .
Wh en S
=
O , S SO i s s e t t o a l o g · c 0 .
The S i d e S e l ec t O u tp u t i s on l y
upd a te d a t t he beg i n n ing o f
a
Type ! 1
o
r I I I command . I t i s
f o r c e d
t<' a
l
o
g
i
c
0 up on
a HASTER
R
E S
ET
c on d i t i o n .
A nom i nal s qu a re-wave c l ock s ign
a l
d e r ive d f rom the d a t a s t r eam
mu�; t be
p ro v i d e d to t h i s i n pu t . P h a s ing
(
i . e .
R CLK
t ra n s i t i o n s
)
r e l a t ive
to
RAW READ
i s impo r t a n t
b u t p o l a r i t y
( RCLK h igh o r l ow ) i s no t .
The d a t a inp u t
s igna l d i rec t l y f rom
t he d r i ve . Th i s i nput
s ha l l be
a
negat i ve p
u l
s
e
f o r
each recorded
f l ux t ra n s i t i on .
The
HLD ou tp u t
c o n t r o l s
the l
o
a d
ing o t
t h e Rea d-Wr i te h e a d
ag a i n s t the me dia .
Th i s ou tput inf orms
the
drive tha t
l i
Re
a
d/
W r
i te head i s pos i t i oned betweP
t ra c k s
44- 7 6 .
Th i s ou t p u t i s
v2 l id
on l y du r ing
Read and Wr i te Comm�nds .