gm82c765b ETC-unknow, gm82c765b Datasheet - Page 4

• Manufacturer Part Number: gm82c765b
• Description: Floppy Disk Subsystem Controller
• Manufacturer: ETC-unknow

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DRV
XT1
CLK1
PCVAL
VSS
STEP
XI
HS
WE
WD
DIRC
DS
DS
MO
DS
1
1
2
3
1
,
DRIVE TYPE
XTAL1
CLOCK1
PRECOMPEN-SATION
VALUE
GROUND
SELECT
STEP
XTAL
HEAD
WRITE
WRITE
DIRECTION
CONTROL
DRIVE
DRIVE
MOTOR
DRIVE
1
PULSE
SELECT
SELECT
DATA
SELECT
ENABLE
ON
1
1
3
2
I
ST
O
ST
I
N
I
N
I
ST
O
HCD
O
HCD
O
HCD
O
HCD
O
HCD
O
HCD
O
HCD
O
HCD
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.
*
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
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
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
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.
4
DRIVE
DRIVE
XT1 (PIN 26) of 44-PLCC
HCD
HCD
SELECT
SELECT
1
2
output,
output,
in PC AT mode, enables the interface
WRITE
in PC AT mode, enables the
DATA
when
when
. Each failing edge of
active
active
GM82C765B
low,
low,
is
is