GM82C765B Datasheet, PDF (4/36 Pages) Hynix Semiconductor – FLOPPY DISK SUBSYSTEM CONTROLLER

GM82C765B
Drive type input indicates to the device that a two-speed
22 24 DRV DRIVE TYPE
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spindle motor is used if logic is O. In that case, the
ST second clock input will never be selected and must be
grounded.
25 _XI1
XTAL1
O XTAL oscillator drive output for 44 pin PLCC should
ST be left floating if TTL inputs used at pin 26.
26 XT1 XTAL1
I
N
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
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CLK1 CLOCK1
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timings for standard data rates. Frequency must be
N 16MHz ± 0.1%, and may 40/60 or 60/40 duty cycle.
* _{XT1 (PIN 26) of 44-PLCC}
PRECOMPENSATION VALUE select input. This pin
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27
PCVAL
PRECOMPEN-SATION
VALUE
I
ST
determines the amount of write precompensation used
on the inner tracks of the diskette. Logic 1 = 125nS,
Logic 0 = 187nS
25 28 HS
HEAD
SELECT
O
HCD
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.
26 29 WE
WRITE ENABLE
O
HCD
This HCD output becomes true, active low, just prior to
writing on the diskette. This allows current to flow
through the write head.
27 30 WD
WRITE DATA
28 31 DIRC DIRECTION
O
HCD
O
HCD
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.
29 32 STEP
STEP PULSE
CONTROL
O This HCD output issues an active low pulse for each
HCD track to track movement of the head.
This HCD output, when active low, is
30 33 _DS1
DRIVE SELECT1
31 34 VSS GROUND
O
HCD
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
32 35 _DS2
DRIVE SELECT2
33 36 ^{MO1 ,}
DS3
MOTOR ON 1
DRIVE SELECT3
O
HCD
O
HCD
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.
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