Pin
No.
Function
I/O
Description
21
WCLK
I
Write data
timing
signal
to
the drive.
250kHz
when in the
FM
mode, and
500kHz
when in the
MFM
mode.
32,31
psa,
1
0
Used
to
specify whether
writing
data
is
to
be
delayed
or
advanced by a specified interval during a
write
operation in the
MFM
mode,
to
ensure a read margin.
These
signals
control
the
WDATA
signal
as
follows:
PSO
PS,
FM
MFM
a a
No
time
change
No
time
change
a
,
LATE
-
225-
250
ns
,
a
EARLY
-
225-
250
ns
, ,
-
-
23
RDATA
I
Data read
from
the drive, comprising
clock
and data bits.
22
WINDOW
I
This
is
created in the
VFO
logic
to
sample the
RDATA.
Phase
synchronization between
RDATA
bits and the
WINDOW
signal
is
done
within
the FDC.
(1) Medium sensor
The host system identifies whether
or
not
a diskette
is
placed
in
the drive, by first sending a SENSE DEVICE
STATUS
command
to
the FDC, then reading the result
status (ST3) from the FDC, and identifying whether
the
MFD
is
in
the READY state or not.
If
the MFD remains NOT READY 800ms after its
motor
is
turned on, the host identifies
that
no disk
is
in
that
MFD.
8·9
VFO
LSI
(HA
16632P)
8·9·1. Characteristics
•
By
a high/Iow change
of
the
control pin, it makes
connection
possible
to
the
8"
or
5"
floppy disk drive.
•
By
a high/Iow change
of
the control pin, it makes input
possible
to
the double-density
or
single-density media.
•
By
a high/Iow change of
the
control pin, it makes
connection
possible
to
any
of
the
UPD765, MB8866,
or
FD1791 floppy disk controller.
•
The
input/output
circuit consists
of
the
LS-TTL circuit_
-42-
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