GM82C765B
Drive type input indicates to the device that a two-speed
spindle motor is used if logic is O. In that case, the
second clock input will never be selected and must be
grounded.
XTAL oscillator drive output for 44 pin PLCC should
be left floating if TTL inputs used at pin 26.
XTAL oscillator input requiring 16MHz crystal. This
oscillator is used for all standard data rates, and may be
driven with a TTL level signal.
TTL level clock input is used to generate all internal
timings for standard data rates. Frequency must be
16MHz ± 0.1%, and may 40/60 or 60/40 duty cycle.
*
XT1 (PIN 26) of 44-PLCC
PRECOMPENSATION VALUE select input. This pin
determines the amount of write precompensation used
on the inner tracks of the diskette. Logic 1 = 125nS,
Logic 0 = 187nS
High Current drive (HCD) output selects the head (side)
of the floppy disk that is being read or written. Logic 1
= side 0. Logic 0 = side 1.
This HCD output becomes true, active low, just prior to
writing on the diskette. This allows current to flow
through the write head.
This HCD output
WRITE DATA
. Each failing edge of
the encoded data pulse stream causes a flux transition
on the media.
This HCD output determines the direction of the HEAD
step motor. Logic 1 = outward motion. Logic 0 =
inward motion.
This HCD output issues an active low pulse for each
track to track movement of the head.
This
30
33
DS1
22
24
DRV
DRIVE TYPE
I
ST
O
ST
I
N
I
N
25
26
XI1
XTAL1
XT1
XTAL1
23
CLK1
CLOCK1
24
27
PCVAL
PRECOMPEN-SATION
VALUE
HEAD
SELECT
I
ST
O
HCD
O
HCD
O
HCD
O
HCD
O
HCD
25
28
HS
26
29
WE
WRITE ENABLE
27
30
WD
WRITE DATA
28
31
DIRC
DIRECTION
29
32
STEP PULSE
STEP
CONTROL
DRIVE SELECT1
O
HCD
31
34
VSS
GROUND
32
35
DS2
DRIVE SELECT2
O
HCD
33
36
MO1
,
DS3
MOTOR ON 1
DRIVE SELECT3
O
HCD
output, when active low, is
DRIVE SELECT1
in PC AT mode, enables the interface
in disk drive. This signal comes from the Operations
Register. In Base or Special mode, this output is #1 of
the four decoded Unit Selects, as specified in the device
command syntax.
Ground
This HCD output, when active low, is
DRIVE SELECT2
in PC AT mode, enables the
interface in disk drive. This signal comes from the
Operations Register. In Base or Special mode, this
output is # 2 of the four decoded Unit Selects, as
specified in the device command syntax.
This HCD output, when active low, is MOTOR ON
enable for disk drive #1, in PC AT mode. This signal
comes from the OPERATIONS Register in the BASE or
Special mode, this output is #3 of the four decoded Unit
Selects as specified in the device command syntax.
HCD
4
HYNIX [ HYNIX SEMICONDUCTOR ]
