BASF 6106 - Page 29

2. 2.
7. 2. READY
DETECTION
The
ready
detector
(Fig.
2
-
25
)
is
used to
on
i tor the
INDEX
pulses
for the
rotational
speed
of
the
disk.
The
INDEX-pulses
are
input
to
the
300
usee
hold-
over-
one
shot.
When
the tine
between
two
consecutive
INDEX- pulses
is
greater
than 3oo
msec,
the
index
counter
is
held
reset. If
the
tine is
less than 300
ms
the hold over
one
shot
is held fired
and
en-
ables the index
counter.
After two
consecutive
INDEX-
pulses
are
clocked
the index
counter
SPEED
is
high
and
the
READY/signal
is sent to
the host
system,
(see timing
diagram
Fig.
2
-
26
)
FROM
INPUT
INTERFACE
1/0 ENA
FROM
INDEX
DETECTOK
fr>
FROM
DC-
CONTROL*
S'iS'li.y.
SPEED/
TM THr
AC'-mm
Lhi) AM.
*
T0
THL
DOCK
l.CHf :„.!VII
i
THE
HEAD
LOAu
C
1
Ki
I 1
T
FIGURE
2
-
25
.
READY
DETECTOR
j,
300 msec
T
.
200
msex
INDEX
300
msec-
OS
FFA
SI'liKD
KHAUY
/
FIGURE
2
-
26 .
READY
TIMING
2-19