Specifications
2.4.2 MFM Read Data
2.6
GENERAL
TIMING
REQUIREMENTS
~
J.
50
nl.e
TVP
1+
~1~ciE;:.c
TYP
°1
-i
~
35l'sec
MAX
~--35I'I.c
MIN
-i
i
400
nlee
MAX
.j
r--
-.t
~
solnaec
MIN
to
150
nlee
MAX
____________
ruui
_
200naec
:t
0.1%
~
~
-
DRIVE
SELECT
--,
-
HEAD
SELECT
---,
81ls
ec
.J
f.
MAX
+MFM
VALID
READ
DATA
-WRITE
GATE
I_
+MFM
WRITE
DATA
(PRE·COMP =
12
nSle SINGLE LEVEL)
2.4.1
MfM Write
Data
This
pair of
signals
defines the transitions
(bits)
to
be
written
on the dlIk. +
MFM
WRITE
DATA
going
more
positive
than
-MFM
WRITE
DATA
will cause •
flux
reversal on the track under the selected head providing
WRITE
GATE
15
active.
This
signal must
be
driven
to
an
Inactive state
(+
MFM
WRITE
DATA
more negative than
-MFM
WRITE
DATA)
by
the host system
when
in
the
rod
mode. Figure 2·10
aho.WI
the
timing
for
MFM
WRITE
DATA.
The data recovered
by
reading a pre-recorded track are transmitted to the host system
via
the
differential
pair
of
MFM
READ
DATA
lines.
This
transition
of
the +
MFM
READ
DATA
line
going more positive than
-MFM
READ
DATA
lines
represents a
flux
reversal on the track
of
the selected head
whUe
WRITE
GATE
is
inactive. See
figure
2·10.
2.5 SELECT STATUS
2·8
FIGURE 2·10.
MFM
READ/WAITE
DATA
TIMING
The
timing
diagram
shown
in
figure
2-11
Ulustrates
the
nec811ary
sequence of eventl (with associated timing restric-
tions)
for
the proper operation of the drive.
Note
that a recalibrate to track 00 sequence
Is
Initiated
at
every
dc
power-on. For this auto-recall sequence
to
func-
tion, the
following
conditions must
be
met:
I Zl. The STEP input at
JS/PS
is
h.ld
active.
b. The spindle
Is
spinning at
Its
regular speed.
I A status
line
is
provided at the
J6/P6
connector to
Inform
the,host system
of
the
selection status
of
th~
drive.
The
DRIVE
SELECT
line
is
driven
by
a
Tn.
open collector
driver'
as shown
in
figure
2-8.
This
signal
will
go
active
only
when the
drive
is
programmed as drive X
(X
iii
1,
2,
3.
or
4)
by
proper placement
of
the shorting
plug
in
the
•
vicinity
of
J5. and
DRIVE
SELECT X
line
at
J5/P5
is activated
by
the host system. See
figure
2-4
for
the jumper
location.