WRITE P ROTECT
selects the Read/Write head on side zero,
the
lower head of th e d r i ve. A t r u e ( l ow) l evel on
this lin e selects the Read/Wr it e h ead on side
one, the upper head of
the drive. When switch-
i ng from one head to th e o t h er, a 100 m i c r o-
second delay is required before any Read or
Write operation can be initi a t ed.
T he Writ e P r o t ect si gnal i s p r o v ided to i n d i -
cate to the user that a wr it e protected diskette
is installed. This signal is t ru e (low) when th e
diskette's W r i t e P r o t ect n o tc h i s u n c overed.
When the Wr it e Pr otect signal is false (high),
t he wr it e e l ectronics ar e en abled, and w r i t e
operations can be
performed.
H EAD LOAD LINE/MOTOR CO N T R O L
READ DATA
T his lin e ma y b e u sed t o c on t rol t h e s p i n dl e
m otor a n d /o r
t h e l e v e r l o c k s o l e n oi d ( s e e
Section 3.6).
OUTPUT CONT ROL LINES
The Read Data line tr ansmits data to the con-
troller when the drive is selected and not
w riti ng. It p r ovides a pulse for each flux t r a n -
sition recorded and detected on
the diskette by
t he drive electronics. Normally, t hi s signal i s
f alse (h i g h) . I t b e c o mes t r u e ( l o w ) f o r t h e
active state.
The Read Data output line goes
true (low) for a duration of 200 nanoseconds,
~ 50 nanoseconds, for e ach c h a nge r ecorded
on the diskette.
There are eight output l i n es, five of which are
standard and three of which are strappable
f eatures. Th e s t a n d ar d o u t p u t s i g n a l s a r e :
I ndex/Sector, T r ac k 0 , W r i t e P r o t e ct , R e a d
D ata, and R eady. The st r a ppable output s i g -
n als ar e D i s k C h a n ge, T w o-Sided, and T r u e
Ready.
READY
INDEX
T he Ready i n t e r f ace signal i n d i c ates a d i sk -
ette has been inserted into the drive. Ready
w ill n o t r e t u r n t o t h e f a l s e s t at e u n t i l t h e
lever is
opened, and is not affected by Spindle
Motor Control.
W hen a
s i n g l e -sided d i s k e tt e i s in s t a l l e d ,
Ready is act iv e ( l ow ) i f s i d e zero is selected.
Ready is false (high) if side one is selected on
t he TM 848-1E. When a t w o -sided diskette i s
installed, Ready is act ive when ei ther side of
the diskette
is
selected on the TM848-2E.
T he Index signal represents the output of t h e
Index sensor. An Index pulse is
provided once
every revolution, 166.67 milliseconds nominal,
t o in dicate t h e b e g i n n in g o f a t r a c k t o t h e
c ontroller. T h e l e a d in g e d g e o f t h i s s i g n a l
m ust a l w a y s be u s e d t o en s u r e t im i n g
a ccuracy. The Index l i n e r e m a ins i n t h e t r u e
(low) state for the durat ion of the Index pulse,
which is nominally four mi l l i seconds.
TRACK 0
TRUE READY
W hen the drive is selected, the Track 0 i n t e r -
f ace signal indicates to the controller that t h e
Read/Write head is positioned on Track 0, the
o utermost t r a c k . T h i s s i g n a l r e m a i n s t r u e
( low) u n t i l
t h e R e a d / W r i t e h e a d i s m o v e d
away from Tr ack 0. This signal is f alse (high)
when the selected drive's Read/Wr it e head is
not on Track 0.
The True Ready int er f ace signal indicates the
d iskette i s r o t a t in g a t 3 6 0 R P M a n d a s e ek
operation is complete, i.e.,
the head has
settled. This may be used to indicate seek com-
plete when using the buffered seek operation.
3-5
